PLATINUM METALS REVIEW · PLATINUM METALS REVIEW VOL. 16 APRIL 1972 NO.2 Contents Platinum Catalysts in Lead-free Gasoline Production 42 Copper-Platinum 48 Alloys 48 Palladium-Silicon

PLATINUM METALS REVIEW

V O L . 1 6 A P R I L 1 9 7 2 NO. 2

Con tents

Platinum Catalysts in Lead-free Gasoline Production 42

Copper-Platinum Alloys 48

Palladium-Silicon Alloys 49

The Carbonyls of the Platinum Group Metals

The Organic Chemistry of Palladium

Wollaston’s Platinum Thermometer 57

Reference Data : Physical Properties of the Platinum Metals 59

Abstracts 60

New Patents 67

A quarterly survey of research on the platinum metals and of developments in their application in industry

Communications should be addressed to The Editor, Platinum Metals Review

Johnson, Matthey & Co Limited, Hatton Garden, London EClP 1AE

42

48

49

50

56

57

59

60

67

Platinum Catalysts in Lead-free Gasoline Production THE PROCESS TECHNOLOGY AVAILABLE

By E. L. Pollitzer Universal Oil Products Company, Des Plaines, Illinois, U.S.A.

Although general application of any process for the production of clear gasoline still has to await a number o j decisions, the necessary technology is already available. This article indicates that, while no single process is likely to provide the complete solution, a combination of processes - in which platinum catalysts will play a signijicant part - will probably be adapted to meet the requirements of individual rejineries.

Concern about air pollution has recently prompted serious consideration of the reduction or elimination of lead alkyls in gasoline. There are two separate and distinct issues involved. On the one hand, lead derivatives are certainly released into the atmosphere, where they are air-pollutants and may be health hazards. In addition to this, lead affects the performance of catalysts which can be used to reduce the level of other pollutants (hydrocarbons, carbon monoxide, nitrogen oxides) in automobile exhaust gas. It has been shown that catalytic converters exhibit excellent performance and durability characteristics when lead-free clear gasoline is used. When leaded gasolines are used, however, the catalysts tend to deactivate.

It is not the purpose of this article to go into details of the pros and cons of lead removal. Rather, we want briefly to address ourselves to the question of the processes that might be applied to the manufacture of clear gasoline and to the role that platinum catalysts are likely to play in such a conversion.

Since the octane number of the U.S. gasoline pool is about 89.5 Research Octane Number (R.O.N.) on a lead-free basis, it is obvious that a boost in octane will be required, although the exact target level is still the subject of discussion. Catalytic reform-

ing has been used to produce high octane blending components in a modern refinery and it would be the obvious process to turn to in any conversion to clear gasoline.

Advances in Catalytic Reforming As far as catalytic reforming is concerned,

the timing is propitious, since significant advances in the area have been made in the last few years. Some of these improvements have been mechanical. For instance, the operation of cyclic regenerative units (Power- forming, Ultraforming, etc.) has been op- timised and improved. In a new approach to the problems of catalyst stability at high severities, U.O.P. has designed and built a continuous Platformer (Fig. I) in which catalyst is continuously withdrawn from the lowest reactor in the stacked configuration, continuously regenerated in an external system and continuously returned to the lead reactor. The smooth, uninterrupted operation of such a unit is recognised as a great advantage.

But perhaps the most publicised advance in the area of catalytic reforming concerned the development of a family of new reforming catalysts which contain a modifier in addition to platinum. The first such catalysts to go into widespread commercial use involved

Platinum Metals Rev., 1972, 16, (2), 42-47 42

Fig. 1. Significant advances have been made i n catalytic reforming i n the last few years. I n this continuous Platformer i n a Texas refinery catalyst is continuously withdrawn from the lowest reactor, regenerated i n an external system and returned to the lead reactor. The smooth and uninterrupted operation of such n unit is a great aduantage

platinum-rhenium combinations. Several Platforming catalysts, Chevron’s Rheniform- such catalysts are available on the market ing catalyst, Engelhard’s E501 catalyst and today including Universal Oil Products’ R-16 one or two others.

Platinum Metals Rev., 1972, 16, ( 2 ) 43

The main characteristic of such catalysts is greatly improved temperature stability (Fig. 2) and, particularly, yield stability (Fig. 3). These comparisons are for runs made at low pressure, low space velocity and high octane number. It should be noted that the initial yield obtained with platinum-rhenium catalysts is identical to that achieved with conventional platinum reforming catalysts (the average yield is, of course, much higher because of improved stability). A new catalyst, called U.O.P. R-20, the composition of which has not as yet been disclosed, appears to differ qualitatively from the earlier versions in that higher yields are obtained from the very beginning of the operation (Fig. 4). (The data in Fig. 4 were obtained at different conditions from those of Fig. 3.)

We can take advantage of the improved performance of the new bimetallic reforming catalysts by making longer runs, using lower pressures, running at higher space velocities, increasing the product octane numbers, or any combination of these parameters. The bimetallic reforming catalysts in use today contain lower platinum levels (somewhat under 0.5 per cent) than some of the earlier all-platinum preparations which contained platinum approaching I per cent. However, it is expected that higher platinum levels may be used in the future as the severity of catalytic reforming increases.

The new reforming catalysts, and catalytic reforming in general, will undoubtedly play an important role in any conversion to clear gasoline. However, some reservations have


been expressed about the desirability of solving the clear gasoline problem by the use of catalytic reforming alone. In a recent seminar for refiners the U.O.P. Process Division pointed out certain shortcomings of such an “aromatic” approach to clear gasoline production. There are published reports, for instance, which claim that highly aromatic gasolines lead to “dirty” engine operation and the formation of excessive engine deposits. This may involve only high boiling aromatics but, in any event, there is a possibility that regulations will be established to limit the endpoint and/or aromatics content of gasoline. One additional factor that may affect such a decision is evidence which points to an increase in the concentration of carcinogenic polynuclear aromatics in automobile exhaust as the aromatics content of the gasoline is increased. It should be noted in this connection that the use of a catalytic exhaust control device would make this point redundant- polynuclear aromatics are very readily adsorbed and very efficiently converted.

There is also the consideration that the volume yields from even the best and most modern catalytic reformer are low compared with those attainable in other processes-an item of considerable importance to the refiner who has to sell gasoline on a volume basis. The most important point, however, has to do with Motor Octane Numbers (M.O.N.) which are receiving increased attention. The sensitivity (R.0.N.-M.O.N.) of aromatics is high and there is a real danger that very high Research Octane Numbers, laboriously attained by very severe reforming will, in some respects, be wasted if the gaosline is judged on a Motor Octane basis (or, according to recent proposals, on the average between Motor and Research Octane).

An Aliphatic Approach Taking all these points into account, it

was suggested at the U.O.P. seminar that we should consider an “aliphatic” rather than an ‘‘aromatic” approach to clear gasoline production. This does not advocate elimina-


Table I Typical Product Distribution Penex

CJC, Isomerisation -. I

Composition Wt %

;so-c, n-C,

cycfo-c,

;so-c n-C,

C, Naphthenes

Octane Number, Unleaded

Research

Motor

Charge

19.3 26.6 1.6

22.6 19.3

5.5

70.1 66.8

Product

36.5 10.9 1.2

38.5 4.8 4.8

83.8 81 .I

tion of catalytic reforming, but it suggests limiting both the volume reformed and the severity of reforming in favour of providing aliphatic high octane components. Basically, the proposal is to upgrade some of the lower octane gasoline components instead of trying to overwhelm them by the addition of high octane Platformate.

This approach will probably involve a number of different processes but it is more than likely that the first step will involve isomerisation of pentanes and hexanes. In many refineries this “light straight run” is blended directly into the gasoline pool with no processing-a procedure that is eminently feasible in the case of leaded gasoline because of the high susceptibility of the paraffins to lead additions.

However, in the casc of clear gasoline the 70 R.O.N. light straight run will be a definite drag on the pool octane. Technology is available today to isomerise these paraffins to more highly branched isomers, bringing the octane number up to well over 90 R.O.N. with little or no yield loss. Since “light straight run” might represent as much as 10 per cent of the total gasoline, such an isomerisation process can obviously mean a gain of 2 + octane numbers on the pool. The products are also high in Motor Octane

Fig. 5 Processes are now available to isomerise parufirrs to more highly brunched isomers, bringing the octane number up to u d over YO R O N with little or no loss of yield. This is a U.O.P. Penex unit, employing platinum catalyst on a highly acidic modijied alumina support, for the isomerisation of CJC, parafins

Number and, furthermore, they add vitally important “front end octane.”

Thermodynamic equilibrium favours the formation of branched isomers at low temperatures. The catalysts used comprise platinum on a highly acidic modified alumina support which permits operation in the temperature range where the equilibrium is favourable. Fig. 5 shows a U.O.P. Penex unit used for CJC, isomerisation, while Table I gives a typical product distribution. Separa- tion and recycle of low octane components is possible but relatively expensive.

Another process that is receiving increased attention in the “aliphatic” approach to clear gasoline is catalytic cracking. Interest in this process has been boosted by the recent development of high severity cracking which produces gasoline of considerably higher

octane number. This octane increase results primarily from the retention and concentration of aromatics and may be subject to some of the limitations mentioned above. However, high severity catalytic cracking also results in increased production of olefins which can be converted to alkylate. Alkylate is produced by the reaction of isobutane with C, or C , olefins and is an ideal clear gasoline component from the point of view of Motor and Research octane number.

A New Catalytic Cracking Process Increased production of alkylate naturally

requires careful consideration of refinery balances.

Low severity cracking does not produce an adequate amount of light olefins. High severity cracking leads to greatly increased


Table I I Overall I-Cracking Yields from

Mid-Continent Naphtha (Isobutane Used to Alkvlate Olefins from

Normal Butane

C, from I-Cracking

C, from Isomerisation

Catalytic Cracking)

Yield Based on Original

Naphtha Charge, LV %

2.7 14.2 12.4

C5+ Platformate

Alkylate

Total C,+ Gasoline

46.7 44.7

117.8 I

Research Clear

Octane Number

93.8 89.0 84.0

105.0 93.5

96.6

olefin yields but now results in a shortage of isobutane. In order to provide the necessary flexibility in a clear gasoline refinery, U.O.P. suggested a new process that has been called “I-Cracking” .

The heart of‘ this process is a very selective low-temperature naphtha hydrocracking step carried out over a highly acidic platinum catalyst. This results in the preferential hydrocracking of paraffins to produce isobutane in addition to some branched C5 and C, components. The remaining C,, product is

Table Ill Overall I-Cracking Yields from

Mid-Continent Naphtha (Isobutane Dehydrog

to Al

Normal Butane

C, from I-Cracking

C, from Isomerisation C,+ Platformate

C, Alkylate

Total C5+ Gasoline

iated and Converted late)

Yield Based ,n Original Naphtha Charge, LV %

2.7 14.2 12.4 46.7 19.1

92.2 -

Research Clear

Octane Number

93.8 89.0 84.0

105.0 98.4

98.4 _.


highly naphthenic and is, therefore, a superior feedstock for catalytic reforming. If the isobutane produced is used to alkylate oiefins from a catalytic cracker, we get the overall product distribution (based on pilot plant data) shown in Table 11.

In an alternate case, the use of I-Cracking need not depend on a catalytic cracker. In a process that is now under development, some of the isobutane is denydrogenated to isobutylene and the mixture is subjected to alkylation, ultimately converting all the isobutane to high octane C, alkylate. The dehydrogenation is carried out over a modified platinum catalyst at high space velocities and low pressures. Per pass conversions range up to 25 per cent or higher with excellent selectivity. The overall product distribution from such a combination process is shown in Table 111.

A Combination of Processes Most Likely

Wide scale application of any new processes for clear gasoline production will obviously have to await a number of decisions. These include not only a timetable for the conversion but also the octane number of the gasoline as well as possible limitations on the aromatic content.

Meanwhile, however, a number of con- clusions can be drawn:

(I) Technology that will permit conversion to clear gasoline at acceptable yield levels is already available.

(2) It is unlikely that there will be a single process that will carry the bulk of the new load-a combination of processes will probably be adapted to any given refinery situation.

(3) Platinum catalysts are likely to play a substantial role in a number of these processes.

Platforming, Platformer, Penex and I-Cracking are exclusive marks of Universal Oil Products.

Copper-Platinum Alloys THE EQUIATOMIC Cu-Pt SUPERLATTICE

R. S. Irani and R. W. Cahn Materials Science Laboratory, University of Sussex, Brighton, England

We have been trying to elucidate the mechanisms of ordering of the lattice structure in various copper alloy systems, among which the copper-platinum system is especially interesting because of its unique features.

The random f.c.c. solid solution in the equiatomic copper-platinum system shown in Fig. Ia is replaced below the critical temperature of 812°C by a long-range ordered rhombohedral lattice. The latter superlattice configuration consists of alternate layers of pure copper and pure platinum atoms arranged parallel to the (111) planes, there being the same number of nearest neighbours in both the ordered and disordered states, as shown in Fig. Ib.

CuPt is the only known superlattice with this structure but in fact surprisingly little work has been performed on the equiatomic alloy. The fact that there is no change in the number of nearest neighbours upon ordering has meant that most existing theories fail to account for the ordering in CuPt. However, Clapp and Moss (I) have attempted a formu- lation in terms of first and second nearest neighbours, the approach being referred to as the central pair-wise (CPW) model. The analysis predicts the long-range order behaviour from short-range order data, obtained by Walker (2) from diffuse X-ray scattering experiments on powdered samples, but there is no mention of why CuPt orders at all. The theory could be more rigorously tested using diffuse X-ray scattering from single-crystal samples of CuPt.

Our recent experimental study (3) has shown that Curt conforms to the earlier established thermodynamic criteria (4) that order-disorder transformations are first-order

phase reactions. Moreover, the structural change involved (a rhombohedral lattice replacing a cubic one) means that substantial internal stresses are created which sub- sequently strengthen the material during rhe course of transformation, as shown in Fig. 2.

Such hardening behaviour, coupled with the corrosion and oxidation resistance of the alloy, can be usefully employed when the


alloy has been annealed for intermediate times below the critical temperature (81zT). A thermal polishing technique (5) for producing strain-free surfaces without recourse to electrolytic polishing, which is impractic- able, has meant that it is now possible to perform polarised light metallography on bulk samples of CuPt (see Fig. 3) and thus interpret the mechanical characteristics in terms of the ordered morphologies.

Further work is in progress and a forth- coming publication will provide full details of our studies.

Palladium-Silicon Alloys The high affinities of both palladium and

platinum for silicon are well known, for dis- astrous consequences result when these metals are heated under reducing conditions in contact with siliceous materials. Although low melting point phases are formed, the alloying processes which result in this eutectic formation have been incompletely understood and since 1957 (I) it has been known that the palladium-silicon diagram originally published in Hansen was inaccurate. Rao and Winterhagen confirmed the existence of the compound Pd,Si but concluded incor- rectly that it reacted directly with pure palladium to form a eutectic melting at 760°C.

Dr E. Roschel and Dr C. J. Raub of the Forschungsinstitut fur Edelmetalle at Schwabisch Gmund (2) have now re-examined the system, using silicon of semiconductor quality, and have revealed a fairly complex situation. As silicon is taken up by palladium, the compounds Pd,Si and PdaSi are suc- cessively formed. Pd,Si and Pd$i melt congruently at 835" and 1070OC and the intermediate compound Pd,Si forms peri-

Fig. 3 Thermally polished sample of equiatomic copper-platinum ulloy observed under polarised light after annealing for 8% at 550'C, showing ordered domains growing from surface imperfec- tions, e.p. grain boundaries and pores

References I P. C. Clapp and S. C. Moss, Phys. Rev., 1966,

2 C. Walker,J. Appl. Phys., 1952, 23, 1x8 3 R. S. Irani and R. W. Cahn, Nature, 1970,

4 F. N. Rhines and J. B. Newkirk, Trans. A .S .M. ,

5 R. S. Irani and R. W. Cahn, Metallography,

142,418; 1968, 171,754; 1968, I7Ii 764

226, I045

19.53, 45, 1029

1971, 4, 91

tectically at 822'C. The first eutectic is formed between pure palladium and PdjSi and melts at 825OC. A second eutectic melting at 798°C then forms between Pd,Si and Pd,Si.

The diagram advanced by Roschel and Raub, although considerably more complicated than that previously accepted, is soundly based on the thermal analysis and metallographic evidence, both of which fix the eutectic compositions very precisely. Al- though the structures of Pd,Si and Pd,Si have not been completely elucidated, their diffraction lines are tabulated in considerable detail and the only remaining uncertainty in this system is the extent of the primary solid solution of silicon in palladium As previously showr? (3) this interstitially dissolved silicon causes discontinuous yielding effects.

A. S. D. References

I N. K. Rao and H. Winterhagen, Trans.

2 E. Roschel and C. J. Raub, Z . MetaZlkunde,

3 R. G. Hollister and A. S . Darling, Platinum

Indian Inst. Metals, 1956-57, 10, 139-148

1971, 62, (11), 840-842

Metals Rev., 1967~ IT, (3), 94-99


The Carbonyls of the Platinum Group Metals By C. W. Bradford Research Laboratories, Johnson Matthey & Co Limited

In recent years improved methods of synthesis have made it possible for the chemistry of the carbonyls of the platinum group metals to be studied more thoroughly. This article reviews the preparation, structure, chemical reactions and uses of these important and interesting compounds.

Complexes where the carbonyl group is the only ligand present have been reported for all the platinum group metals except palladium. These compounds are listed in the table.

The colourless volatile ruthenium and osmium pentacarbonyls are unstable in ultraviolet light at room temperature and decompose to give the trinuclear dodecacarbonyls. Recently irradiation of Os(CO), at -4o'C has led to the isolation of Os,(CO), (I). The analogous ruthenium compound has not yet been prepared although the iron compound Fe,(CO), has been known for many years.

Carbonyls of the Platinum Group Metals

Ru(CO), RhdCO) 12* Colourless Red m.p. -22T dec. I30-14Ooc

Orange Black m.p. 153°C dec. 197-208'C

OS(CO), Colourless Yellow m.p. -15°C dec. 23oOC

Orange-yellow Red dec. 6447°C

OS,(CO)l,* Yellow m.p. 220°C

m.p. -melting point dec. =decomposes * These compounds are now available from Johnson Matthey & Co. Limited.

RudCO) IL* RhdCO)1.5*

IrdC0)12 Ptn(C0) zn Cherry-red

0 s K 0 ) B Irdc0)I6

Platinum Metals Rev., 1972, 16, (2), 50-55

The existence of Rh,(CO), and Irz(CO)8 analogous to the cobalt carbonyl Co,(CO), was claimed by early workers in this field but attempts by others to repeat the original preparations have been unsuccessful. All that has been obtained is some infrared spectral evidence for the reversible formation of Rh,(CO), from Rh,(CO),, under high pressure of carbon monoxide at low temperature (-19°C).

No substantiated reports have been published on platinum or palladium compounds similar to the nickel carbonyl Ni(CO),. Thus the polymeric platinum dicarbonyl is the only known carbonyl of these two metals and even this compound is unstable in air.

A number of heteronuclear platinum metal carbonyls have also been prepared recently, e.g., Ru,OS(CO)~, and RuOs,(CO),,.

Methods of Preparation Until recently all the preparative methods

with the exception of that for Ptn(CO),, involved the use of carbon monoxide at moderately high pressures (10 to 200 atm).

The recommended method for the preparation of Ru,(CO),, is to treat ruthenium acetylacetonate in methanol solution with a 3 :I mixture of carbon monoxide and hydrogen at 160 atrn pressure at 165°C (2). The preparation can be simplified by preparing the ruthenium acetylacetonate in situ by using ruthenium trichloride hydrate and sodium acetylacetonate. Os,(CO) can be prepared

50

by treating OsO, in methanol (3) or xylene (4) solution with carbon monoxide at 175 atm, 175°C. The pentacarbonyls Ru(CO), and Os(CO), can both be obtained by the above methods using heptane as solvent. This increases the yield of the pentacarbonyls and decreases that of the dodecacarbonyls (5).

Recently Ru,(CO),, has been prepared by passing a stream of carbon monoxide through a solution of ruthenium trichloride hydrate in refluxing 2-ethoxy-ethanol to give a ruthenium carbonyl chloride solution, which was further carbonylated to the dodecacarbonyl by addition of zinc and ethanol and continuation of the refluxing and treatment with carbon monoxide (6). An alternative atmospheric synthesis is to pass carbon monoxide through a propanol solution containing ruthenium oxoacetate [Ru,O(O,CCH,),(H,O),]O,CCH, and a base such as triethylamine at 85°C (7).

The two rhodium cluster carbonyls were first prepared by reduction of anhydrous rhodium trichloride with carbon monoxide at 200 atm using a metal (e.g., copper, zinc or silver) as halogen acceptor. At temperatures of 50-8o"C the main product was Rh,(CO),, whereas at 8o-23o0C the only product was Rh6(CO)16. More recently Rh,(CO),, has been prepared at atmospheric pressure and room temperature in aqueous solution by reduction of [RhCI,]'- to [Rh(CO),Cl,]- with copper metal and carbon monoxide, followed by further reduction with carbon monoxide and water in the presence of sodium citrate buffer (8). Rh,(CO),, has also been prepared under similar mild conditions by reducing [Rh(CO),CI] , with carbon monoxide in water-alcohol solution in the presence of lithium acetate (9).

The iridium carbonyl Ir,(CO)l, can be prepared in 50 to 60 per cent yield by reacting iridium trichloride with carbon monoxide under pressure in aqueous methanol solution in the presence of sodium bicarbonate (10).

Reduction of a suspension of Ir4(CO)l, in tetrahydrofuran with sodium yields first the anion [Ir,(CO),,H]-, then [Ir,(CO),,]2- and finally [Ir(CO),]-. If the intermediate

hexairidium ion is isolated as the tetra- ethylammonium salt and suspended in acetic acid in a carbon monoxide atmosphere for several days the neutral red carbonyl 1r8(CO),* is precipitated (11).

The unstable polymeric platinum dicar- bony1 Ptn(CO)2n has been obtained as a cherry red precipitate by the action of carbon monoxide on aqueous (12) or ethanolic (13) solutions of Pt" compounds (e.g. K,PtCl,) a t temperatures up to 80°C; or as a purple colloidal precipitate by the action of water on a benzene solution of Pt(CO),Cl, under an atmosphere of carbon monoxide (13).

Structures The infrared spectra of Ru(CO), and

Os(CO), suggest that they both have the same trigonal bipyramidal structure as Fe(CO),.

In crystalline Ru,(CO),, and Os,(CO),, the metal atoms form an equilateral triangle, each being bound to four terminal carbonyl groups, two approximately perpendicular to and two parallel to the plane of the triangle (Fig. I). The mixed metal carbonyls Ru *Os( CO) and RuOs,( CO) I , probably have similar structures. It is interesting to note that in Fe,(CO),, two of the iron atoms are bridged by two carbonyl groups. The absence of bridging carbonyl groups in the ruthenium and osmium compounds, in which


the triangular cluster is held together by metal-metal bonds alone, is indicative of the increase in the strength of metal-metal bonds on going down a transition metal triad.

The structures of Rh,(CO),, and Ir4(CO)lz are shown in Figs. 2 and 3; that of the rhodium compound is similar to Co,(CO),,. Thus in this triad the transition from a carbonyl bridged to a non-bridged structure occurs between the 2nd and 3rd row transition elements and not between the 1st and 2nd row elements as in the iron group triad.

The structure of Rh,(CO),, is shown in Fig. 4. Four of the carbonyl groups are bridging three rhodium atoms.

It is thought that the platinum carbonyl Pt,(CO),, is monomeric in solution but pentameric in the solid state (12).

Bonding in Metal Carbonyls The ability of the carbonyl group to stabilise

metal atoms in low positive, zero, or low negative oxidation states is believed to be due to the fact that the carbonyl group not only donates a lone pair of electrons to form a cs bond but can also accept back electrons to form a r bond. More specifically there is first a dative overlap of the filled carbon 0 orbital with an empty metal 0 orbital and second a dative overlap of a filled dTi or hybrid dpx metal orbital with an empty antibonding pn orbital of the carbon monoxide (Fig. 5).

The effect is synergic as the drift of electrons to the metal in the 0 bond tends to make the CO positive, thus enhancing the acceptor strength of the x orbitals. Similarly, the drift of metal electrons into CO TC orbitals tends to make the CO negative and hence increase its basicity via the carbon cs orbital.

Carbonyls bridging two metal atoms are considered to be similar to organic keto-type bridges. The carbon forms sp2 c orbitals which means that there can be only one C-0


x bond. The metal-carbon T: bonding is more complicated than with terminal carbonyl groups and may be multicentre in character. For carbonyl groups which bridge three metal atoms simultaneously no simple picture is possible and multicentre bonding must be invoked with bonding electrons assigned to molecular orbitals.

Reactions During the last five years the reactions of

the noble metal carbonyls, cspecially those of Ru3(CO),, and Os,(CO),,, have been investigated in some detail. The most notable feature is the stability of the metal atom clusters and the increase in this stability on going from the second to the third row transition elements.

All the carbonyls react with neutral ligands such as triphenylphosphine to give substituted species. Whereas with Ru,(CO),, only the trisubstituted compounds Ru,(CO),L, (L =phosphine ligand) have been isolated, in the case of Os,(CO),, all three derivatives Os,(CO),,~,L, (x= 1-3) are obtained. In these compounds only one carbonyl group is substituted on any one metal atom. Further work with Os,(CO),, using less PPh, has led to the separation of six more products in which there are examples of bridging PPh groups, bridging phenyl groups, co-ordinated “benzyne” C,H,, and loss of hydrogen atoms from phenyl groups

with concomitant formation of 0s-C 0 bonds. The tetra- and hexa-rhodium carbonyls

react to give Rh,(CO),, .xL, (x = 1-4) and Rh,(CO),,~,L, (x =6 or 9) respectively, although the reactions may easily be taken further to Rh p ( CO),L,.

Ir4(CO)12 reacts to form Ir4(CO)12-xLx (x=2, 3). The structures of the substituted derivatives differ from the parent carbonyl by having three bridging carbonyl groups.

Substituted products have also been obtained with bidentate ligands and in in- stances where crystal struczures have been determined the ligands bridge adjacent metal atoms.

The reactions of the trinuclear carbonyls Ru,(CO),, and OS~(CO),~ differ significantly towards halogens. At low temperatures RU,(CO)~~ gives cis Ru(CO),X, (X-halogen) which on warming trimerises to Ru,(CO),,X,; this loses carbon monoxide to give [Ru(CO),X,], which on pyrolysis under vacuum at 2oocC goes to [Ru(CO),X,],.

With Os,(CO),,, however, one 0s-0s bond is initially ruptured to give Os,(CO),,X,. This compound loses two molecules of carbon monoxide on refluxing in benzene for 24 hours giving Os,(CO),,X, in which the two halogen atoms bridge the two osmium atoms which have lost the carbonyl groups. Further chlorination of Os,(CO),,Cl, breaks the remaining 0s-0s bonds yielding a mixture of [Os(CO),Cl,], and cis Os(CO),CI,.


The two rhodium carbonyls react with halogens to give Rh,(CO)&.

The type of structure exhibited by Os,(CO),,C1, has been found to be quite common among the derivatives of the trinuclear carbonyls. For example, thiols, RSH, react to give HM,(CO),,(SR), (M-Os, Ru) which contain bridging hydride and SR groups, and OS, (CO)~~ reacts with Ph,PAuCl to give Os,(CO)lo(AuPPh,)C1 with bridging chlorine and AuPPh, groups.

Reactions with other metal halides give different results, however. Stannic chloride reacts at room temperature giving M,(CO),,(SnCl,)Cl, while mercuric halides in boiling xylene form M(CO),(HgX),.

The rhodium carbonyls react with thiols to give thiolato bridged dimers Rh,(CO),(SR),, the tetrarhodium carbonyl reacting at room temperature and the hexarhodium carbonyl in boiling toluene.

Both the trinuclear carbonyls can be protonated by concentrated sulphuric acid to give the cations [HM,(CO),,]t (M =Ru, 0s ) which have been isolated as the [PF,]- salts. The cations decompose on heating to give [HM(CO)J+ which can also be obtained by direct protonation of M(CO),.

Rh,(CO),, decomposes in cold concentrated sulphuric acid but Rh,(CO),, dissolves to give a cationic species. Ir4(CO)lz dissolves slowly at room temperature to give a stable protonated species which has been formulated as [H,Ir,(CO)lz]2 +. Attempts to isolate solid [PF6]- salts of the hexarhodium and tetrairid- ium cations have not been successful.

Reaction of potassium hydroxide in methanol with RU~(CO)~, and Os,(CO),, gives anionic species which on acidification form the hydridocarbonyls H4M4(C0),,, H Z M ~ C O ) ~ ~ , HOs8(CO)dOH) and H,O%(CO),,.

Under reflux in carboxylic acids Ru,(CO),, reacts to give [Ru(CO),(RCO,)I,. The acetate forms the dimer [Ru(CO),(CH,CO,)], on reaction with carbon monoxide under pressure. With Os,(CO),, the dimer is obtained directly by reaction in a sealed tube

at 170°C. Rh,(CO)l, reacts slowly with acetic acid to give [Rh(CO),(CH,CO,)], and metallic rhodium.

Reaction of the trinuclear ruthenium and osmium carbonyls with acetylenes leads to the formation of numerous mono-, bi- and trinuclear compounds. Eight derivatives have been isolated from the reaction of Ru,(CO),, with diphenylacetylene and one of these Ru,(CO),[PhC,Ph], exists as two isomcrs, one containing a Ru, cluster with no bridging carbonyls which is easily trans- formed to a more stable isomer having a metallacyclopentadiene ring and bridging carbonyl groups.

Reaction of M,(CO)12 with silanes, stan- nanes and germanes (R,M’X), (M’=Si, Sn, Ge), under various conditions leads to the formations of compounds of the general formula (R,M’),M(CO), and in the case of osmium the hydrides R,M’Os(CO),H. Dimeric species such as [R,S~OS(CO),]~ and [(Me,Sn)Ru(CO),(SnMe,)] are also obtained. In the latter compound the two ruthenium atoms are bridged by two SnMe, groups.

Uses of the Carbonyls As well as being the starting materials for

the preparation of many other compounds as described above, these carbonyls, especially the ruthenium and rhodium compounds, act as catalysts in a number of organic syntheses.

For example, Ru,(CO),, promotes the homogeneous reduction of nitrobenzene to aniline by carbon monoxide and hydrogen at 200 atm, 160°C (14). Yields in the order of 66 per cent are obtained. The stoichiometry of the reaction is probably:

C&NO, + 2CO + H,---tCGHjNH, + 2COZ

At CO:H, ratios higher than I, diphenylurea is formed as a byproduct. A reaction mechanism has been proposed in which a phenylnitrene intermediate stabilised by bonding to ruthenium undergoes either hydrogenolysis to give aniline or carbon monoxide insertion and hydrogenolysis to give z,z’ diphenylurea. Other nitro com-


pounds have been similarly reduced to amines. Ru,(CO) 12 also catalyses the carbonylation

of acetylene to hydroquinone (15). Yields of 60 per cent are obtained in tetrahydrofuran solution at 200°C using 120 atm carbon monoxide plus 10 atm hydrogen.

0- 2CZHz + 2CO + HZ-+HO-

Water or alcohol can also be used as the source of hydrogen and similar yields of hydroquinone obtained.

A third example of the catalytic activity of Ru,(CO),, is in the hydroformylation of olefins. A typical reaction is the conversion of propylene to butyraldehyde which proceeds at a good rate at 150°C with carbon monoxide and hydrogen under pressure to give 70 per cent yields (16).

The two rhodium carbonyls have also been used as hydroformylation catalysts, e.g. Rh4(CO),, for the hydroformylation of r.-heptene at 75"C,40 atm (17)~ and Rh, (CO),, for the hydroformylation of cyclohexene (I 8).

It is not always the carbonyl alone that is used as the catalyst. For example, Rh6(CO),, together with PPh, catalyses the IOO per cent conversion of I-hexene to a mixture of 2-

methylhexaldehyde (27 per cent) and n- heptaldehyde (73 per cent) by reaction with with a I :I mixture of carbon monoxide and hydrogen at 82OC, 35 atm (19).

There are fewer examples of the use of the osmium and iridium carbonyls as catalysts. However, these compounds will probably be important in studying the course of reactions, the slower reaction rates enabling intermediates to be isolated.

Although no catalytic uses of Rn(CO),, as such have been described in the literature it has been postulated that carbomethoxy derivatives of platinum carbonyls are catalytically active in the electrochemical synthesis of methyl esters of c(, p unsaturated carboxylic

acids from olefins under 70 atm carbon monoxide (20). The platinum compounds are formed by electrolysis under carbon monoxide pressure of a solution of sodium methoxide in methanol using platinum electrodes.

It is hoped that now a number of the platinum group metal carbonyls are more readily available further uses will be found both for the carbonyls themselves and for their derivatives.

References References have only been given for the methods of preparation and the uses of the platinum metal carbonyls. For further details of the reactions of metal carbonyls in general the excellent reviews of E. W. Abel and F. G. A. Stone inQuartmh Reviews (1969, 23, 325 and 1970, 24, 498) are recommended.

I J. R. Moss and W. A. G. Graham, Chem. Comm., 1970,835

2 G. Braca, G. Sbrana and P. Pino, Chim. e Ind. (Milan), 1964, 46, 206

3 B. F. G. Johnson, P. A. Kilty and J. Lewis, J . Chem. SOC. (A) , 1968,2859

4 C. W. Bradford and R. S. Nyholm, Chem. Comm., 1967, 384;J. Chem. Sac. (A) , 1971, 2038

5 F. Calderazzo and F. L'Eplattenier, Inorg. Chem., 1967~6, 1220

6 J. L. Dawes and J. D. Holmes, Znmg. Nucl. Chem. Letters, I971,7, 847

7 B. R. James and G. L. Rempel, Chem. and Ind., 1971, 1036

8 S. Martinengo, P. Chini and G. Giordano, J . Organometal. Chem., 1971, 27, 389

9 P. Chini and S . Martinengo, Inorg. Chim.

10 S . H. H. Chaston and F. G. A. Stone,J. Chem. SOC. (A) , 1969,500

11 L. Malatesta, G. Caglio and M. Angoletta, Chem. Comm., 1970,532

12 K. I. Matveev, L. N. Rachkovskaya and N. K. Eremenko, Izvest. Sibirsk Otdel. Akad. Nauk. SSSR, Ser.Khim. Nauk, 1968,2, 81

13 G. Booth, J. Chatt and P. Chini, Chem. Comm.,

14 F. L'Eplattenier, P. Matthys and F.

15 P. Pino, G. Braca, G. Sbrana and A. Cuccuru,

16 G. Braca, G. Sbrana, F. Piacenti and P. Pino,

17 B. Heil and L. Marko, Chem. Ber., 1968,

18 N. S. Imyanitov and D. M. Rudkovskii, Zh.

19 G. Foster and M. J. Lawrenson, Ger. Offen.

20 T. Inoue and S. Tsutsumi,J. Am. Chem. SOC.,

Acta, 1969~31 315

1965,639

Calderazzo, Znorg. Chem., 1970, 9, 342

Chem. and Ind., 1968, 1732

Chim. e Znd. (Milan), 1970, 52, 1091

101,2209

Prikl. Khim., 1967, 40, (9), 2020

1,9013145

1965, 87,3525


The Organic Chemistry of Palladium The Organic Chemistry of Palladium, by Peter M. Maitlis. Vol. I, Metal Complexes, 324 pp., E8.85. Vol. 2, Catalytic Reactions, 234 pp., E7.45. Academic Press, New York and London, 1971

The notion that a metallic element should have an ‘organic chemistry’ associated with it should come as no surprise to anyone who has graduated in chemistry in the past decade, or who has kept even half an eye on the recent chemical literature. Of the platinum group metals, none has a more extensive, interesting and useful ‘organic chemistry’ than palladium, and the recently published two-volume work by Professor Peter Maitlis is both welcome and timely.

Metal Complexes The first of these two volumes is entitled

‘Metal Complexes’. It comprises a thorough and up-to-date review of the great variety of complexes formed by palladium (usually in the +2 oxidation state) with unsaturated organic molecules, especially olefins, acetylenes and diolefins. The nature of the bond between the metal and the organic molecule is quite well understood, and one of the valuable results arising from the discovery of these compounds has been the extension of our understanding of valency theory and a realisation of the limitations of classical bonding symbolism. This point is especially relevant in the chapter on it-allylic complexes and in the shorter final chapter on cyclo- pentadienyl and benzene complexes.

Catalytic Reactions The second volume, entitled ‘Catalytic

Reactions’, will be of greater interest to synthetic organic chemists and to those seek- ing to employ the powerful techniques of homogeneous catalysis in the design of new processes of industrial significance. I t is perhaps worth emphasising the pre-eminent position of palladium and its complexes in

this area. It appears to be a consequence of a fortunate concatenation of circumstances, in that palladium not only forms the right sort of complexes, but that they are sufficiently reactive to be effective intermediates in catalytic processes. This is, for example, not the case with platinum, where although similar complexes exist they are too stable to be reactive.

Professor Maitlis organises his material according to the type of bond which is formed or broken: thus there are chapters on the formation and cleavage of carbon-carbon bonds , carbon-oxygen bonds, carbon- hydrogen bonds and carbon-X bonds where X is halogen, nitrogen, sulphur or silicon. There is a fmal short chapter on heterogeneous reactions which has the value of comparing homogeneous and heterogeneous palladium catalysts.

It has been something of a disappointment to those who have worked long and hard in the fields of palladium complex chemistry and of homogeneous catalysis that so few large-scale industrial applications have yet emerged. It has not been for want of effort but those who place value upon the commercial relevance of their work may take heart; the difficulties which have inhibited industrial applications have been in the chemical engineering rather than in the chemistry of the systems. What is required now is more attention to the technology of homogeneous catalysis, so that what is known may be used fruitfully.

These two volumes are much to be wel- comed and will long continue to be consulted by those who are interested in the interface between inorganic and organic chemistry.

G . C. B.


Wollaston’s Platinum Thermometer By J. A. Chaldecott The Science Museum, London

The achievements of William Hyde WOllaStOn are well documented in the literature concerning the platinum metals and their early utilisation in science and industry. He it was who first showed the way to produce malleable platinum on a commercial scale - incidentally the first successful example of powder metallurgy - and he was the discoverer of two new elements in native platinum which he named palladium and rhodium (I , 2).

Fortunately he left a considerable quantity of notebooks and memoranda recording both his experiments and his financial transactions, most of these still preserved in the care of the University of Cambridge and others in the Science Museum, and it was in the course of examining his miscellaneous income and expenditure accounts that the writer came across an entry of particular interest. This records a payment to one Malacrida of the sum of 19s for two platinum thermometers (3).

It appears that one of these two thermometers was intended for the use of Wollaston’s scientific and financial partner Smithson Tennant, the discoverer of iridium and osmium, for among the miscellaneous Wollaston papers preserved at Cambridge there exists a loose sheet of paper on which is written “Platina Thermometer, for Mr Tennant”. The other was presumably employed by Wollaston himself.

So far as the writer is aware no reference has been made in the literature to such a thermometer, nor has any description of it been given. There is some reason to suppose, however, that it was of the bimetallic type, with platinum as one of the compound metals and that it was a forerunner of the many kinds of thermostatic element’s that are now so widely employed.

William Hyde Wollaston From a sketch made with thc camera lucida by

Sir Francis Chantrey

In his paper to the Royal Society, in 1805, “On the Discovery of Palladium” (4, Wollaston described his use of the bimetallic principle to obtain a rough idea of the linear coefficient of expansion of palladium:

I rivetted together two thin plates of platina and of palladium; and observing that the compound plate, when heated, became concave on the side of the platina, I ascertained that the expansion of palladium is in some degree the greater of the two. By a similar mode of comparison I found that palladium expands considerably less than steel by hcat; so that if the expansion of platina between the tcmpera- tures of freezing and boiling water be estimated at 9 parts in 10,000, while that of steel is known to be about 12, the expansion of palladium will probably not be much more or less than 10, or one part in 1,000 by the same difference in temperature.

It is clear that this particular experiment of Wollaston’s was not designed for measuring temperature, and the riveted device should in


A n extract from one of Wollaston’s notebooks. This includes referenres t o one Sylvester of Shefield soldering steel wire to platinum and platmum to zinc, and ( in the lower part) to his soldering of platinurn iLith gold by blot+ pipe while the metal was surrounded with hot rharcoul

no sense be regarded as a bimetallic thermometer. But from a short account given by Andrew Ure in 1821 in his Dictionary of Chemistry (5) we learn that in 1809 Wollaston had shown him

‘a slip of copper coated with platinum, which exhibited by its curvature, over flame, or the vapour of water, the expanding influence of heat, in a striking manner’.

It seems unlikely that Ure would have used the word “coated” to describe a bimetal formed by riveting, and it is interesting to speculate on the precise method of attaching the two metals.

Now among some of Wollaston’s notebooks covering the period 1807 to 1809 there are references to a Sylvester of Sheffield, almost certainly one Charles Sylvester, who has been described as formerly a plated wire worker and as becoming an eminent practical chemist. The notebooks record Wollaston as supplying Sylvester with 28 oz. g dwt. of platinum in December 1805 , and in the same month, the fact that Sylvester was soldering platinum with gold, using a blowpipe. In 1807 Sylvester also apparently soldered platinum to zinc and bonded together steel wire and platinum, using silver as his joining medium. One of the notebooks also records, in March 1807, Sylvester’s plating with platinum, and it seems further that he had

succeeded in rolling copper plated with platinum on one side until the bimetal was about 0.1 inch in thickness. The Wollaston material also contains a scrap of paper on which is listed the following sequence of operations :

‘ 1 Platina well anneald 2 Metal jlatted & then anneald 3 Clean Fled 4, Well tinned 5 Platina tinned 6 Metal hot enough to melt the solder 7 Platina rolled on’.

The handwriting is not that of Wollaston. Could this be Sylvester’s recipe for coating a metal with platinum ? And was it perhaps the method adopted for making a bimetallic strip for a platinum thermometer ?

The problem remains unsolved, and the writer has been unable to trace the identity of Malacrida or the nature of his connection with the platinum thermometers.

References I Donald McDonald, “The History of Platinum”,

London, Johnson Matthey & Co Limited, 1960 2 L. F. Gilbert, “W. H. Wollaston MSS. at

Cambridge”, Notes and Records, Royal Society,

3 J. A. Chaldecott, Annals of Science, 1971, 27, 409. This gives a more fully documented account of the entries in the Wollaston material, and forms the basis of the present article

4 W. H. Wollaston, “On the Discovery of Palladium”, Phil. Trans., 1805~95,316

5 Andrew Ure, “A Dictionary of Chemistry”, London, 1st edition, 1821, article on “Thermo- meter”

1952, 9, 311


PHYSICAL PROPERTIES OF THE PLATINUM METALS Platinum Metals Review last published a table o f the properties of the six platinum metals in October 1963. This revised table includes some more recently determined values and i s

expressed in SI units where appropriate.

Atomic number..

Atomic weight . . Thermal neutron

cross section, barns _ . ..

Lattice structure

Lattice constants atZO'C,A a

C/O

Density a t 20"C, kg!m3 .. ,.

Melting point, "C

Thermal conducti- vity at 0-IOPC, W / m K . .

Specific heat at O°C,JjkgK ..

C o e f f i c i e n t o f linear expansion at 20-1OO0C, XI06 . . ..

Vapour pressure a t 1500"C, Torr

Resistivity at WC, pohm.cm . .

Temperature coefficient of resistance at 0- 100°C . . . .

Thermal e.m.f. against platinum at 1000°C, mV

Mass susceptibi- l i ty x, cm3/g, XI06 . . ..

Thermionic function, A/cm2K2

W o r k function 9, v .. . .

Tensile strength, annealed, Ib/inz, xIO' . . kN/m2, x l o 3 . .

Modulus of elasti- city in tension, Ib/in2, x106 .. kNhn2, x106..

Hard ness,annealed, Hv .. . .

Platinum

78

195.09

9 5 1

F.c.c.

3.9229

21 450

1768

73

131 .2

9.1

10-6

9.85

0.0039

+0.9712

64

5.27

18 1 24

25 172

40-42

Iridium

77

192.22

425515

F.c.c.

3.8392

22650

2443

148

128.4

6.8

10-

4.71

0.0043

+ 12.73

+0.133

170

5.40

160 1100

75 516

200-240

Osmium

76

190.2

15.31t0.7

C.p.h.

2.7340 1.5799

22610

3050

87

129.3

6.1

10-'2

8.12

0.0042

+0.052

1 20

4.8

81 556

300-670

Palladium

46

106.4

6.0+1.0

F.c.c.

3.8906

1 lo20

1552

76

244.3

11.1

10-2

9.93

0.0038

-1 1.505

+5.231

60

4.99

25 172

17 117

4042

Rhodium

45 102.9055

150+5

F.c.c.

3.8029

12410 1960

150

246.4

8.3

10-6

4.33

0.0046

$14.05

+0.9903

100

4.90

100 688

46 31 6

100-102

Ruthenium

44

101.07

3.0&0.8

C.p.h.

2.7056 1.5825

12450

2310

105

230.5

9.1

10

6.80

0.0042

+9.760

$0.427

> 4.54

72 496

60 41 7

200-350


ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES Contribution on the Inner Oxidation of Platinum-(lOo/, Rh-)l% Zr Alloys G. REINACHER, Z. Metallkunde, 1971, 62, (11), 835-840 Thealloys I wt.q/,Zr-Pt(I)andr wt.?, Zr-1owt.x Rh-Pt (XI) can be internally oxidised by heat treatment in air at 850 and 1o0o"C. At 1400°C both alloys form oxides only in the grain boundaries, which stops further oxidation. The alloys suffer a decrease in hardness with increased heat treatment temperature, the reduction being 50% with I and I O ~ ; , in 11.

Interdiffusion and Compound Formation in Thin Films of Pd or Pt on Si Single Crystals J. DROBEK, R. c. SUN and T. c. TISONE, Phys. Status

Electron transmission observations of Pt- Si diffusion couples show that the compounds Pt,Si, Pt,Si and PtSi form during diffusion. Pt,Si disappears as diffusion proceeds, leaving a film of a mixture of 35-40:/0 Pt,Si and remainder PtSi. In PdSi diffusion couples the dominant phase is Pd,Si, with only small amounts of PdSi formed after vacuum annealing.

Sohdi, A, 1971, 8, (I), 243-248

On the Age-hardening of Fe-Pt-Mn Alloys M. TANAKA and T. SUZUKI, J . Japan Inst. Metals, 19713 35, (IO), 974-979 Strain-hardening due to formation of a coherent zone, probably Pt-Mn /3 phase, is a major factor of age-hardening. There is an extended miscibility gap island compared with Fe-Ni-Mn. The strain hardening response increases in Fe-Pt-Mn alloys when precipitation of the coherent zone occurs. The f.c.t. Pt-Mn ,B1 phase with Cu-Au type structure is observed in aged Fe-Pt-Mn alloys.

Electrical Resistivity and Magnetic Suscepti- bility of Amorphous Cr-Ni-Pt-P Alloys

5186 Amorphous alloys of the composition (Cr, Ni0.3n-XPt0.,0)0.,5P0.2j) where o <x i0.06, were synthesised by rapid quenching of the melt. The base alloy, for which x=o, is non-magnetic and has a negative temperature dependence of resistivity at 4.2 <T C400K. Cr additions give rise to an additional temperature dependent negative resistivity contribution. This can be correlated with the presence of localised magnetic moments on Cr atoms, and consequent Curie-Weiss behaviour of the I ~ L against T curves.

A. K . SINHA,J. Appl. PhyS., 1971, 42, (I2), 5184-

Thermodynamic Properties of the Gold-Pal- ladium System Measured with a Dual- chamber Knudsen Cell Mass Spectrometer Combination Technique D. c. BARTOSIK, Diss. Abstr. B, 1g71,32, (6), 3478B The activity and potential heats of mixing of the components in the solid Au-Pd system at I473K were measured. The activities of both exhibit negative deviations from ideality for alloys with >zoat.q;, Pd or with :>So at."a Au. The integral excess entropy and enthalpy are both negative for all alloys up to 80 at.yu Au. The electronic structure of the alloys is discussed.

imperiecx iviisni uisiocarivns iu inin r inns of Silver on Palladium

5640-5643 A study of the energy of complete and potential misfit dislocations indicates that the misfit between a (0 o I ) Ag film and a Pd substrate will be accommodated by partial misfit dislocations. The extrinsic stacking faults associated with these partials are expected to lie in the Ag film and to modify its crystal structure.

X-ray Determinations of the Debye Tern- peratures and Thermal Expansions for the Pd-Ag-Au System s. v. N. NAIDU and c. R. nousKA,J. Appl. Phys.,

X-ray measurements of the Debye characteristic temperatures Om and the coefficient of thermal expansion for the Pd-Ag-Au system are presented. Lattice parameters and integrated intensities of Bragg reflections are calculated for the temperature range 80-298K. For all alloys the pre- dominant lattice disturbance is due to thermal vibration. Griineisen's relationship between the mean square atomic vibration amplitude and the thermal expansion for cubic solids is valid for these alloys with yZ2=0.167.

The Field Dependence of Electron-Paramag- non Scattering in Nearly Ferromagnetic Pd- Ni Alloys A. I . SCHINDLER and B. c. LAROY, Solid State Covnmun., 1971,9, (zI), 1817-1820 The temperature dependence of the electrical resistivity of dilute paramagnetic Pd-Ni alloys was measured in applied magnetic fields of up to 93 kG. Increasing field strength causes the s electron-paramagnon scattering coefficient to decrease, this tendency being stronger with increasing Ni concentrations.

-

J. W. MATTHEWS, 3. Appl . Phyx., 1971, 42, (I?,),

1971, 42, (121, 4971-4975


The Structure of the Ternary Copper-Nickel- Palladium Allays at Temperatures from 400 to 700°C E. RAUB, 0. LOERICH, w. PLATE and H. KRILL, Z. Metallkunde, 1971, 62, (II), 826-830 The structure of ternary Cu-Ni-Pd alloys with up to 60 at.?(, Pd was investigated using X-rays at qoc-700cC. At low Pd concentration a miscibility gap exists in which two disordered f.c.c. phases are in equilibrium below 675°C. The w ~ P two phase region exists in a wide range of ternary alloys. I t is in equilibrium with the two phase region ctI + c t 2 below 500°C.

Levitation Calorimetry. IV. The Thenmo- dynamic Properties of Liquid Cobalt and Palladium J. A. TREVERTON and J. L . MARGRAVE, J . Pkys. Chew., 1971,75, b4), 3737-3740 Levitation calorimetry was used to study the thermodynamic properties of liquid Pd. AHm= 3940 f70 cal/g .atom, ASm = 2.16.ko.04 cal /degK/ g.atom, C,(I) =9.18 cal,'degK,g.atom. The emissivity of the liquid metal surface -0.374 i0.004.

Large Magnetic Scattering in Fe-doped Pd- hased Alloys R. P. GUERTIN, I. TURNER and w. s. WEINTRAUB, Phys. Lett. A, 1971, 37A, (41, 309-310 The low-temperature electrical resistivity of several paramagnetic Pd-based alloys with -1000 p.p.m. Fe was measured. A very large contribution to the resistivity by the Fe impurity is observed for both the Pd-Rh and Pd-Pt series.

Magnetic States in Amorphous Fe-Pd-Si Alloys R. HASEGAWA, J . Phys. Chem. Solids, 1971,32, (11), 2487-2492 The electrical resistivity, magnetic susceptibility and magnetoresistivity of amorphous Fex(Pd,, SilB)l,n-x, where x varies between 0.1 and 0.9, were measured. The polarisation of the d- electrons of Pd atoms around a Fe atom persists down to the lowest Fe concentration. No giant moment is observed. Interactions between the d-electrons of the Fe atoms, resulting in a supermagnetic behaviour of the alloys below a characteristic temperature, occurs only at higher fields.

Mossbauer Effect Study of Amorphous Fe-Pd-Si Alloys T. E. SHARON and c. c. TSUEI, Solid State Commun.,

The Mossbauer spectra of amorphous FexPds,, Si,, (where o<:x-:7), were measured at 4.2, 77 and 295K. Results are not typical of a superparamagnetic system and a model is proposed for the magnetism in these alloys based on a local ferromagnetic order whose direction changes randomly throughout the material.

1971, 9, (221, 1923-1927

The Palladium-Tungsten Phase Diagram below 1100°C H. R. KHAN and c. J. RAUB,J. Less-common Metals, I971,?5, (4), 441-442 The phase diagram for 5-90 at.?< W-Pd below I 100°C was investigated. Reduction at 500-700"c gave a homogeneous phase only with 5 at.':.; W, samples containing more W consisting of f.c.c. Pd and b.c.c. W phases. After annealing at 700°C for 1000 h, alloys containing up to 15 at. W con- sisted of the f.c.c. Pd phase only. For 20-70 at.?;; W the f.c.c. Pd and b.c.c. W phases were present. From graphical data it is concluded that the phase boundary of the f.c.c. Pd solid soiution exists between 15 and 20 at.#,!(" W at 700°C. Additional X-ray lines were observed which may be due to an intermediate phase.

Influence of the Crystalline Electric Field on the Kondo Resistivity of CexLal_,Pd3 Ter- naries v. u. s. RAO, R. D. HUTCHENS and J. E. GREEDAN, J . Phys. Ckein. Solids, 1971, 32, (12), 2755-2759 The electrical resistivities of the cubic CexLa,, Pd, ternary alloys were measured at 2-300K; the alloys are all of single phase except between 0.3 <x .::0.5. Resistivities indicate the presence of the Rondo effect, and some alloys display a maximum in their resistivity/temperature curve and also an additional minimum at low temperatures. An explanation is given in terms of the influence of the cubic crystalline field on the Ce ions.

Thermoelectric Power of Pure Rhodium

2610-2612 The thermoelectric power of Rh was measured at 4-300K. A peak of +2~v/K was found at q 5 K , but none at 2gK, in contrast to previous results. The reasons for the peak are discussed.

Low-temperature Heat Capacity of Ni". 62RhO. 38 B. B. TRIPLETT and N. E. PHILLIPS, Phys. Lett. A, 1971,374 (9,443-444 The magnetic field dependence of the anomalous heat capacity of Ni,,.,,2Rh,,.38 at low temperatures is consistent with superparamagnetic behaviour of ferromagnetic clusters, but not with spin fluctuation effects.

Metastable F.C.C. Fe-Rh Alloys and the Fe-Rh Phase Diagram c. c. CHAO, P. DUWEZ and c. C. TSUEI, 7. Appl. Phys.,

Single phase metastable f.c.c. Fe-Rh alloys were prepared by rapid quenching from liquid, and the lattice spacings and Fe5: Mossbauer spectra were measured at room temperature, lattice parameters and isomer shifts both vary smoothly with Rh concentration.

D. J. HUNTLEY, CUn. 3. PhYS., 1971, 49, (20),

1971, 42, (111,4282-4284


The Ru-Sc Constitution Diagram E. M. SAVITSKII, V. P. POLYAKOVA and N. B. GORINA, Izv. Akad. Nuuk S. S. S. R., Metally, 1971, (6), 161-163 The Ru-Sc system contains the phases Ru,Sc, RuSc and RuSC,, the latter detected for the first time. Properties vary with alloy composition according to Kurnakov’s Law.

CHEMICAL COMPOUNDS On the Composition and Structure of Pt,O,

Nemg. Khim., 1971, 16, (IZ), 3190-3194 PtOl.ls is prepared by thermal decomposition of hydrated PtO , with subsequent chemical treatment. X-ray studies showed that the synthesised oxide agreed structurally with f.c.c. Pt,O,.

Tetracarbonyls of Palladium and Platinum in Low Temperature Matrices

OZIN, Nutwe Phys. Sci., 1972, 235, (57, Jan. 31), 98-100 Matrix isolation was used to stabilise simple carbonyl species of Pd and Pt for I.R. spectroscopic analysis. The species were produced by reaction of the monoatomic metal vapour and CO in Ar. Spectroscopic results indicate the presence of Pd(CO), and Pt(CO),.

Platinum. A Noble Metal, “Base” Atoms

A. M. SWHOTIN, E. A. GANKIN, YU. D. KONDRASHOV, YU. A. OMEL’CHENKO and B. YA. SHAL’MAN, Zh.

H . HUBER, P. KUNDIG, M. MOSKOVITS and G. A.

P. S. SKELL and J. J. HAVEL,J. Am. Chem. SOC., I971,93, (24), 6687-6688 Pt atoms generated in vacuo from a W filament at 1950°C were deposited simultaneously with a large excess of an organic compound on the walls of the container vessel which were cooled to -196°C. The Pt atoms reacted with C,H,, 1-C4H8, 1,s-cyclo-octadiene and 1,3-butadiene to form organometallic complexes, some of which are catalysts.

Investigation of the Conditions of Formation of Palladium Borides

IVANCHENKO, Zh. fiikludnoi Khim., 1971,4, (IO),

Thermal, X-ray and metallographic studies analysed the direct synthesis of Pd,B from its elements at 7m900OC for 5-6 h and of Pd,B, at 800-950°C for 60-70 h. These phases melt at I I IO&ZO and 11g0&zoOC respectively. The microhardness of Pd,B is 470240 kg/mm2.

Dissociation of Tris(tripheny1phosphine)- chlororhodium(I) in Solution H. ARAI and J. HALPERN,~. Chem. SOC., D, Chem. Commun., 1971, (23), 1571-1572 The equilibrium constant for the dissociation of

G. V. SAMSONOV, V. A. KOSENKO and V. G.

2304-2306

RhCl(PPh,), to RhCI(PPhs), and PPh, was found spectrophotometrically to be (1.4io.4) X IO-~M in C,H, at 25°C.

La,Sr,,RuO,: A New Perovskite Series

Chm., 1972, 4, (I) , 80-86 LaRuO, was prepared for the first time; it is metallic and antiferromagnetic. Solid solutions with ferromagnetic SrRuO, of the type LaxSrl.-x RuO, exist for all values of x; ferromagnetism diminishes rapidly with increasing La content. All compounds show Curie-Weiss behaviour at low temperatures. The properties and structure of LaRuO, are discussed.

Kinetics of Nitrogen Uptake by Ruthenium (11) Aquospccies L. A. P. KANE-MAGUIRE, 3. Inorg. Nucl. Chem.,

The kinetics of complex formation between N, and the Ru(I1) complexes ~~S-[RU(A-A),(H,O),]~+ (A-A =(NH,),, ethylenediamine, + triethyl- enetetramine) were studied. The species [Ru(A-A) z(H,0)N,12-’- and (TRu(A-A),(H,O)I , NJ4+ were identified by U.V. spectrometry. The kinetic results show the formation of the N, complexes to be almost independent of the Ru complex used.

Oxidative Addition Reactions of Triphenyl- phosphine with Dodecacarhonyltrios- mium(0): Benzyne-, Phenyl-, and Related Complexes of Osmium

J. M. GUSS, P. R. IRELAND and R. MASON,J. Chem. SOC., Chem. Commun., 1972, (z), 87-89 Reaction of Os3(CO)12 with PPh, in the mole ratio of I :2 gives a mixture of products, three of which were defined by X-ray crystallography as

(Ph)(PPhC,H,) and Os,(CO),(PPh,),(C,H,).

Beryllides of Ruthenium, Osmium, Rhodium, and Iridium of Composition M,Be,,

R. J. BOUCHARD and J. F. WEIHER, J. Solid state

1971,333 (111,3964-3966

C. W. BRADFORD, R. S. NYHOLM, G. J. GAINSFORD,

HOSs(CO),(PPhJ(PPh,C,HJ, Os,(CO),(PPh&

L. F. VERKHOROBIN, G. P. KOVTUN, A. A. KRUGLIKH, N. N . MATYUSHENKO, N. S. PUGACHBV and G. F. TIKHINSKII, Izv. Akad. hbuk S.S.S.R., Metully, 1971, (6), 168-171 7-16 at.?; M-Be alloys (M=Ru, Os, Rh, Ir) contain isomorphous M,Be,,, structure P 6 / m . Lattice parameters are Ru,Be,,, a =4.zo3 i0.004 and c=10.90&0.01~; Os,Be,,, a=4.221 k0.004 and c = ro.gg&o.or 1\; Rh,Be,,, a-4.19oio.004 and c-10.88 +O.OI A; Ir2BeI7, a==4.193+0.004 and c-10.89i0.01 A.

Synthesis, Structure and Reactions of Chelate Metal-olefin Complexes R. s. NYHOLM, P w e Appl. Chem., 1971, 27, (I+), 127-144 Organometallic complexes in which the metal is


coordinated to an olefinic bond in the ligand are reviewed. The bonding structure, coordination, reactions and isomerisation of such compounds, many of which include Pt metals and Au, are discussed.

The Development of Transition Metal Chemistry in the United States of America J. c. BAILAR, Ibid., 1-21

The study of complex inorganic compounds in the U.S.A. over the past century is reviewed. Some Pt metal organometallic complexes are discussed as examples of specific types of complex.

ELECTROCHEMISTRY Surface Films on Platinum and Tungsten Carbide Anodes K. VON BENDA, H. BINDER, A. KOHLING and G. SANDSTEDE, Battelle Frankfurt Inform., 1971, (I I), 46-52 The electro-oxidation of CH,OH, HCOOH, CO and H, on Pt anodes with adsorbed surface films was studied. The variations in oxidation rates at different potentials due to the nature of the adsorbed surface films are discussed.

The Hydrogen/Oxygen Titration of Platinum Films M. AKHTAR and F. c. TOMKINS, Trans. Faraday soc., 1971,675 (8),2454-2460 The surface area of evaporated Pt films was obtained by measuring uptake of H, subsequent to chemisorption of O2 at 196 K. The effect of raising the temperature in vacuo and in the presence of 0, was studied. The surface area obtained refers to the area catalytically active for the Hz + 0, reaction at that temperature. “Active” area determinations have an accuracy of 3-404.

Effect of Presorption on Platinum Films of Catalytic Oxidation of Hydrogen and Area Determination by Carbon Monoxide/Oxygen Titration Ibid., 2461-2468 The effect of presorbed H,O, CH,OH and NH, on Pt films on the catalytic oxidation of H, at 195 K was studied. Substantial amounts of H, molecules were associatively chemisorbed on the presorbed primary layer of water and were rapidly oxidised by O,(g). A mechanism for this process is proposed.

Role of Structural Factors in Electrocatalysis. I. Smooth Platinum Electrodes v. s. BAGOTSKII, YU. B. VASILIEV and I. I. PYNSHNOGRAEVA, Electrochim. Acta, 1971,16, (Iz),

Adsorption of H, 0, CH,OH, Br- and HS0,-, evolution of HZ and 0, and electro-oxidation of CH,OH were studied on different faces of a Pt monocrystal and on annealed polycrystal samples

2 I 4 1-2 I 67


with structural defects. Adsorption isotherms were almost identical, but process rates on faces with densest atomic packing were highest. Neither unsaturated surface atoms nor lattice defects act as active centres governing the catalytic properties of the whole surface. The bond energy changes little from one face to another of the monocrystal or with the number of defects. The shape of the adsorption isotherm seems to be governed by electronic properties.

Study of the Kinetics of Electrochemical Reactions by Thin Layer Voltammetry. IV. Influence of Chemisorbed Species on the Reactions of Platinum Complexes at Plati- num Electrodes A. L. Y. LAU and A. T. HUBBARD, J . Electroanal. Chem. Interfac. Electrochem., 1971, 33, (I), 77-93 The rates of electrode reactions of acidoammine Pt (11) and (IV) complexes were measured in halide solutions using Pt electrodes treated with irreversibly chemisorbed substances. The chemisorbed substances displaced most of the specifically adsorbed halide, shifted the potentials in the diffuse double layer to more positive values and sterically hindered the reactions.

Proton Injection in the Highly Conducting Mixed Valence Square Planar Platinum Complex K,.,,Pt(C,O,),.xH,O. New Solid State Proton Galvanic Cell F. N. LECRONE and J. H. PERLSTEIN, J . Chem. SOC., Chem. Commun. 1972, (z), 75-74 Single crystals of K,.,,Pt(C,O,),.xH,O display non-ohmic behaviour in applied electric fields which is associated with proton injection at the anode. The half cell reactions associated with this proton migration constitute a new solid state proton battery with cell potential in the range 0.3-0.5 v. Hydrogenation of Propargyl Alcohol at Controlled Potentials on Palladium

SOKOL’SKII, Zh. Fiz. Khim., 1971, 45, (IZ), 3097- 3101 The rate and selectivity of hydrogenation of propargyl alcohol on Pd can be controlled by imposing a potential on the catalyst. The absolute selectivity of saturation of pmpargyl alcohol in ally1 alcohol is reached at positive potentials.

N. A. ZAKARINA, G. D. ZAKUMBAEVA and D. V.

ELECTRODEPOSITION AND SURFACE COATINGS A Technique for Selective Electroless Plating N. FELDSTEIN and T. S. LANCSEK, R.C.A. Rev.,

A process for the selective electroless plating of metals on dielectric substrates involves the selective deactivation of an adsorbed stannous layer

1971, 32, (2)J 306-310

above specially patterned films. The principal reactions are discussed. The process results in the formation on the substrate surface of finely divided catalytic Pd nuclei which are essential for the initiation of the plating process.

Universal Electroplating Instrument for Gold, Rhodiuq Platinum Baths, etc. Pinturas y Acabados Znd. (Barcelona), 1971, 13,

A universal laboratory plating unit suitable for the electrodeposition of Au and Pt group metals is described.

(59), Io*IO4

HETEROGENEOUS CATALYSIS Sumitorno CNA/WNA Process. Integrated High Pressure Nitric Acid Plant Nitrogen, 1971, (74L 38-39 Sumitomo Chemical Engineering Co. have developed a system capable of producing 98 wt.Y(, and 70 wt.Oo HNO, in any desired proportion. NH, is burnt with air over a Pt-Rh gauze catalyst, giving an NO yield of 96O,,. The concentrated acid is obtained by adsorption of further N oxides in moderate strength acid followed by distillation.

Dual Catalysis Increases the Efficiency of Ammonia Oxidation Nitrogen, 1971, (741, 41 A procedure developed by the Polish Instytut Nawozow Sztucznych combines the use of a Pt or Pt-Rhgauze and a fixed bed metal oxide catalyst such as a mixture of Cr,O,, Fe,O,, graphite and an oxide promotor. This gives substantial reduction in the excess 0, required for a given conversion efficiency; NO, formation is kept to a minimum and the resultant condensate is of very low strength.

Effect of Electrolyte Composition on Charg- ing Curves of Skeleton Platinum-Iridium Catalysts

VOVCHENKO, Vest. Moskov. Univ., Ser. II, Khim., 1971, (51, 619-620 Electrolyte composition affects the amount of H, adsorbed by Pt-Ir catalysts and the adsorption energy. Adsorption capacity decreases in the order HCl, H,SO,, KOH.

Effect of Thermal Treatment on the Proper- ties of Platinum Catalysts L. I. STOLYARENKO and A. v. VASEV, Elektrokhimiya,

The amount of 0, absorbed during heat treatment was measured for three Pt black catalysts prepared by different methods. The increased stability of one catalyst was due to the preparation process in which intense reaction of Pt and O 2 took place. Increase in the surface 0, concentration increases the stability for heat treatment.

A. D . SEMENOVA, N. V. KROPOTOVA and G. D.

19719 7, (91, 1380-1382

Hydrogenation of 3,7'-Dimethylenebicyclo- [3,3,1]-nonane on Platinum Catalysts

A. G. YURCHENKO and A. P. KWNOSHCHEK, Zh. Org. Khim., 1971, 7, (IZ), 2516-2519 In addition to the three stereoisomeric 3,7- dimethylenebicyclo-[3,3, I,]-nonanes formed during the hydrogenation of 3,7-dimethylenebicyclo- [3, 3, I,]-nonane over Pt in various solvents there are products of incomplete hydrogenation.

The Preparation of Pt-Alumina Catalyst and Its Role in Cyclohexane Dehydrogenation

c. ADD INK,^. Catalysis, 1971, 23, (I), 105-117 The preparation from H,PtCI, and properties of Pt /Al,O, were studied. Catalytic activity for dehydrogenation of cyclohexane at 150°C de- pended on Pt concentration, not on the preparation method. Dehydrogenation is zero order at atmospheric pressure and 150°C.

F. N. STEPANOV, E. N. MARTYNOVA, L. A. ZOSIM,

R. W. MAATMAN, P. MAHAFFY, P. HOEKSTRA and

Catalytic Reforming of Petroleum on Plati- num/Alumina Catalysts Promoted by Rare Earth Elements

v. v. SHIPIKIN, Khim. Tekhnol., Topliv. Masel,

Tests on 0.5 wt.:', PtiAl,O, with 0.1 wt.76 Y and 0.05 wt. yo Ce additions showed that catalysts promoted by these elements possessed greater activity, selectivity and thermal stability in petroleum reforming than unpromoted catalysts.

Effect of the Pretreatment of a Platinum/ Alumina Catalyst Promoted by Yttrium on Its Activity in the Hydrogenation of Benzene V. A. POLIKARPOV and G . M. SEN'KO, Dokl. Akad. Nauk Belorus. S.S.R., 1971, 15, (6), 523-524 The activity of a Pt/Al,O, catalyst was increased when promoted by I wt.":, Y . The catalyst was preferably pretreated with H, at 300-400'C.

N. S. KOZLOV, V. A. POLIKARPOV, G. M. SEN'KOV and

1972, (11, 1-4

Catalytic Activity of Platinum on Delta- alumina in the Hydrogenation of Ethylene. I. Catalytic Activity of Non-calcined Catalyst G. PAJONK and s. J. TEICHNER, Bull. SOC. Chim. Fr., 1971, (111,3847-385s Pt/Al,O, catalyst was prepared by impregnating 6-A1203 with H,PtCl, in CH,OH. The Pt crystallite size was measured. The kinetics of hydrogenation of C,H, at 0°C over this catalyst followed the Langmuir-Hinshelwood model. CzH4 is adsorbed associatively and inhibits the reaction; H is weakly adsorbed. The support does not affect the catalytic activity. TI. Catalytic Activity of Granulated Cal- cined Catalyst Ibid., (IZ), 4235-4242 The activity of the calcined catalyst was roo


times less than that of the non-calcined catalyst. C,H, hydrogenation follows the same mechanism. C2H, is chemically and physically adsorbed on to the catalyst surface. Several explanations are advanced to account for the lower catalytic activity. 111. Catalytic Activity of the Calcined Cat- alyst in Powder Form Ibid., 4242-4246 When the Pt/Al,O, catalyst used above was ground into powder form the activation energy for C,H, hydrogenation was lowered; the order of the reaction was unchanged. The catalytic activity Im' of Pt was simultaneously increased. The activity of the catalyst is determined by its chemical not its diffusional character.

Catalytic Dehydrocyclisation of Hydrocar- bons. 111. Aromatisation of Hydrocarbons with Six Carbon Atoms on Chromium Uxide and Alumina or Platinum and Alumina

Bull. Sac. Chim. Fr., 1971, (12), 4463-4470 The aromatisation of hexane, I-hexene, a-hexene, 2-methylpentane and methylcyclopentane was studied. Highest yields of aromatic products were obtained using Pt!A1,0,; this catalyst, however, promotes isomerisation of normal hydrocarbons into branched or cyclopentanic hydrocarbons.

M. PERKEE-FAUVET, D. HERAULT and B. BIOURI,

Catalytic Activation of Platinum Deposited on Metallic Aluniinium S. WITEKOWA and P. MATYJEWSKI, Roczniki Chem., 19711 43Y (101, 1729-1737 Pt!A1 catalyst was prepared by precipitating Pt from H,PtCl, on to A1 dust. Activities of Pt/Al, Pt black and Pt /neutral carrier for oxidation were compared. The specific activity of PtiAl was intermediate between Pt black and Pt /neutral carrier. The Pt is dispersed on the A1 surface mostly in the form of a monoatomic layer.

Hydrogcn Chemisorption on Platinum Ca- talysts

H, chemisorption on Pt and Pd on active C and Also, was measured by rapid desorption effected by increasing the temperature from 21 to 370°C. The results show that dispersion of Pt on active C was 47, 32 and 23uh for 0.5, 1.0 and IO:;;, Pt/C.

Rapid Measnrement of Hydrogen Chemi- sorption by Supported Catalytic Metals H. A. BENESI, L. T. ATKINS and R. B. MOSELY, J. Catalysis, 1971, 23, (z), 211-213 Surface areas of catalytic metals such as Ptisilica gel can be found by measuring the evolution of chemisorbed H, in a flowing I mole H,-Ar mixture. The catalyst is equilibrated at 0°C and then heated to 500°C to desorb H,. Chemisorp- tion values obtained for the metal surface area agree with those obtained using static techniques.

C. E. HUNT,J. Catalysis, 1971, 23, (I), 93-96

Catalytic Hydrogenation of But-2-yne on Palladium-Gold Alloys H. G. RUSHFORD and D. A. WHAN, Trans. Faraday S0C.j I971,67, (Iz), 3577-3584 The hydrogenation of but-a-yne was investigated on Pd-Au wires at 263-638K. Pd-rich wires were active at the lower temperatures and Au-rich wires at the higher. Results suggest that Au acts as a diluent, the active sites being islands of four adjacent Pd atoms. The cisitruns ratio of but-2- enes produced fell from 99 : I for pure Pd to 4.2 : I for 97 at.:h Au-Pd.

Kinetics of Selective Hydrogenation of Dimethylethynylcarbinol on Palladium in the Vapour Phase

and S. L. K I P E W , Kinet. Kataliz, 1971, 12, (6), 1455-1463 Studies of the kinetics of selective hydrogenation of dimethylethynylcarbinol into dimethylvinyl- carbinol in the vapour phase over Pd in a cir- culating system showed that the ration of the rate of reaction to the degree of conversion passes through a maximum not connected with diffusion or change of selectivity, Kinetic equations define the mechanism of the process.

Dispersion and Activity of Palladium on Aluminium Oxide

D. 2. LEVIN, M. A. BESPROZVANNYI, F. A. MELAMED

N. T. KULISHKIN, A. V. IMASHKINA, N. E. BUYANOVA, A. P. KARNAUKHOV, I. D. RATNER and L. M. PLYASOVA, Ibid., 1539-1545 Various methods showed that the dispersion of Pd on A1,0, decreases as its concentration increases from 0.3 to 18 wt.:C. The decrease is not abrupt; the total Pd surface and the activity of unit weight of catalyst increase. The specific activity for unit surface of Pd in the hydrogenation of unsaturated sulphones is not related to the dispersion of Pd.

Hydrogenation Refining of Ethylene Frac- tion on a Palladium Catalyst M. SYKORA, Chem. Prumysl, 1971,21, (II), 546-550 Pd catalysts for the hydrogenation of C,H, to C,H, were studied. With Pd/kieselguhr at constant 0.1 wt.";" Pd content the activity de- pended on the specific carrier surface area and increased linearly with increasing surface area. The activity also increased with increased Pd content, Pd/cc-Al,O, catalysts containing 0.1 wt.oi; Pd showed higher activity than those on kieselguhr and the activity did not depend on the specific A1,0, surface area.

Properties of Palladium/Polyvinyl Alcohol Catalysts, Prepared with Alkali Additions L. A. CHIMAROVA and 0. A. TYURENKOVA, Zh. Fiz.

Khim., 1971, 45, (12)~ 3102-310s Studies of the effect of added alkali on the activity of Pd jpolyvinyl alcohol catalysts showed that


catalysts with small amounts of added alkali gave higher rates of hydrogenation of dimethylethynylcarbinol than catalysts without alkali. As the amount added rose the rate of reduction decreased. The catalyst with alkali was adequately stable for eight months and had high selectivity.

Dealkylation of Alkylbenzenes on Rhodium/ Alumina Catalyst G. L. RABINOVICH, G. N. MASLYANSKII and L. M. TREIGER, Kinet. Kataliz, 1971, 12, (6), 1567-1569 Studies of the dealkylation of toluene into C,H, over 0 . 6 ~ ~ Rh,'y-Al,O, at 430°C and at atmospheric pressure showed that the rate of hydrode- alkylation of toluene is 2.5-2.7 times greater than that of dealkylation with H,O vapour. Dealkyla- tion of m-xylene with H,O vapour is selective and gives toluene and C,H, as products.

HOMOGENEOUS CATALYSIS Role of Hydrogen Chloride and Characteris- tics of Catalyst Surface in the Oxycyanation of Ethylene H. NAKAJIMA, Kogyo Kagaku Zasshi, 1971,74, (S ) , 1539-1543 The synthesis of acrylonitrile from C,H,, HCN and 0, was studied over a Pd catalyst. The catalyst surface strongly adsorbs cyano ions and radicals. The rate of oxycyanation is slow but the reaction is highly selective.

Selectivity of Isomers in the Oxycyanation of Propylene over Palladium Catalysts Ibzd., 1544-1549 The oxycyanation of C,H, over Pd and PdCl, was studied to measure the distribution of isomers, viz. methacrylonitrile, crotonitrile and allylnitrile. The ratios were 5 : 40 : 55 respectively with a fresh Pd catalyst, 34 : 50 : 16 with a steady state Pd catalyst and 20 : 42 : 37 over PdC1,.

The Effects of the Ligands on the Oxy- cyanation Catalysts Ibid., 1549-1551 Effects of ligands on the Pd catalyst in the oxycyanation of C3H6 were investigated. Ligands of low rank in the spectrophochemical series gave high catalyst activity probably due to their decreasing the coordination strength of the cyano ion to Pd. Ligands containing I, such as iodide, iodate, periodate and o-iodobenzoic acid, gave the same increase in activity, due to co-ordination between the I atom and Pd atom.

A Study of the Inclusion of Dienes through x- Ally1 Bonds of x- Alkenylinetalhalides. 11. The Inclusion of Butadiene L. YA. AL'T, A. I. WUTKINA, A. M. LAZUTKIN and YU. I . ERMAKOV, Kinet. K a t a h , 1971, 12, (6), 1410-1416 With z-allylpalladiumchloride and -bromide the inclusion of the first molecule of butadiene at the

ir-ally1 bond occurs at a rate about two orders greater than that of subsequent development of polymer chain. When a-allylpalladiumiodide reacts with butadiene, x-crotylpalladiumiodideumidide is formed as well as polymerisation products. The reaction rate when using the chloride or bromide is in the ratio I : 2 to the initial catalyst concentration, and is directly proportional to the butadiene concentration.

Investigation of the Isomerisation and Hydrogenation of Olefins in the Presence of Homogeneous Palladium Catalysts on a Dimethylsulphoxide Base

KOPYTTSEV, Izv. Akad. NaMk S.S.S.R., Ser. Khim., 1972, (I), 201-203 The homogeneous catalyst of Pd with dimethylsulphoxide accelerates conversion of pentenes at ZOT, p H % z 1 atm. C = C bond migration in pentene-1 occurs at a greater rate than hydrogenation, and cis-pentene-2 is converted faster to trans-pentene-a than to pentane. The processes apparently occur with partial coordination of H,; no isomerisation is observed in the absence of H,.

Catalytic Coupling of Aromatics and Olefins by Homogeneous Palladium(I1) Compounds under Oxygen R. s. snw, J. Cham. SOC., D, Chem. Commun., 1971, (231, I510-15II The coupling of aromatics such as C,H, and olefins such as styrene, cyclohexene, etc., is catalysed by homogeneous Pd(I1) complexes, especially Pd(OAc), under mild 0, pressure.

Kinetics and Mechanism of Hydrogenation of Cyclohexene Catalysed by Chlorotristri- phenylphosphinerhodium(1) in Benzene s. SIEGEL and D. OHRT, Inorg. ATUcl. Chem. Letters, 1972, 8, (I>, 15-19 The kinetics and mechanism of the hydrogenation of cyclohexene catalysed by Cl(PPh,),Rh(I) in CBHa were studied. The complex w a s slightly dissociated. At low alkene concentration and I atm. H, most of the catalyst is present as Cl(PPh,),RhH, formed by dissociation of the complex followed by uptake of H, then of free PPh,.

ELECTRICAL AND ELECTRONIC ENGINEERING An Improved Autogenic Hydrogen Reference Electrode K. BINDER, A. KOHLING and G. SANDSTEDE, Chem.- I%.-Tech., 1971, 43, (IS), 1084-1088 The electrode uses Raney Pt, and can be used without calibration for galvanostatic, potentio- static, potentiodynamic and pulse measurements in strongly acidic or alkaline electrolytes. No additional Ha is required.

L. KH. FREIDLIN, N. M. NAZAROVA and YU. A.


The Effect of Corrosion, Electrical and Mechanical Loading on the Behaviour of Contact Materials E. BAIER, Verbindungstechnik, 1971, 3, (3), 17-18 The properties and applications of electrical contact materials made of a number of precious metals and alloys including Au, Ag and Pt group metals are reviewed.

Report on British Corrosion Group Meeting British CurrosiunJ., 1971, 6, (5), 192-193 The use of PtITi for impressed current anodes and their performance, wear and efficiency were discussed. Tests indicated that wear rates of Pt are -1-z;igiamp hour. Reduction in life-time is probably due to acidity. An anode with 100y in Pt should last 3-6 years at IOO amp/ftz.

TEMPERATURE MEASUREMENT Platinum Resistance Thermometers for Pre- cise Measurements up to 1100°C w. HEYNE, Exp. Tech. Phys., 1 9 7 1 , 19, (z), 1 4 3 -

150 Improvements of the IPTS at 630-1064°C were sought using Pt resistance thermometers for interpolation in place of Pt : Rh-Pt thermocouples. Low-resistance thermometers were made for 60 mm immersion having a 10 mm diam. ceramic insulator, with double wound coils of Pt wire 0.25,0.3 and 0.5 mm thick enclosed in quartz tubes. After 4oh the resistance change from thermal effects is to.008 deg Cih at 1060'C and less than io .001 at o'C. The thermal resistance changes did not depend on wire diameter unlike impurity effects. Only 0.5 mm wire had suitable precision as regards the latter.

NEW PATENTS METALS AND ALLOYS Nitrogen-free Platinum

British Patent 1,254,033 The manufacture of Pt powders, for use in metallising compositions and the production of printed circuits, which are relatively coarse- grained and free from N,, is described. Pt is precipitated by Zn from an aqueous PtCI4 solution, HCl is added until no further reaction is observed and the precipitate is filtered off, washed and dried.

E. I. DU FONT DE NEMOURS & CO.


Relative Pressure Dependence of Chromel/ Alumel and Platinum/Platinum-lO"~ Rho- dium Thermocouples D. LAZARUS, R. N. JEPPERY and J. D. WEISS, Appl.

Measurement of the relative thermal e.m.f.s of Chrome1 : Alumel and Pt : 1076 Rh-Pt thermocouples up to 7 kbar indicate a pressure correction for Pt couples of 0.57&0.03 deg C;kbar from 600-1000°C. Systematic differences of unknown origin are found between pressure corrections measured with increasing and decreasing pressure.

Control of a Steel Ingot Intermediate Heating Furnace H. KLAMMER, Inscrtim. Prac., 1 9 7 2 , 26, (I), 31-33 Pt : Rh-Pt thermocouples are used to sense temperature in a comprehensive instrumentation system which controls the furnace temperature automatically. The system is designed with a view to computer control in the future.

High Precision Therniometry Using Indus- trial Resistance Sensors A. THULIN,J. Phys. E: sci. Instrum., 1 9 7 1 , 4 , (10) ,

764-768 Stability tests on glass-embedded and glass- bonded Pt wire IOO ohm sensors show that reproducibility in temperature measurement of a few millidegrees can be obtained when working below 150'C if the sensors are thermally cycled over the intended range of measurement prior to calibration.

Thermocouples for above 1500 OC E. D. ZYSK and A. R. ROBERTSON, Instrum. Technol.,

The use of thermocouples made of Pt, Rh, Ir, W, Re and other refractory metals in a variety of combinations is described for high temperature applications.

P ~ Y s . Lett., 1971, 19, (101, 371-373

1971, 18, (111, 30-38

CHEMICAL COMPOUNDS Hydride and Carbonyl Triphenylphosphine Derivatives of Kuthenium and Osmium

U.S. Patent 3,597,461 Pentacoordinate complexes of Ru and 0 s have the general formula M(CO),-,[P(C,H,),],, where M is Ru, 0 s and n is 1,2. They are prepared by reacting the corresponding pentacarbonyls with triphenylphosphine. Dihydride compounds of formula MH,(CO),~(C,H,),], (M=Ru, 0s) are also described.

AMERICAN CYANAMID CO.

Reforming Catalyst CHEVRON RESEARCH co. British Patent 1,253,408 A catalyst for reforming of naphtha consists of a

ELECTRODEPOSITION AND SURFACE COATINGS Metal Plating of a Nonconductive Substrate R.C.A. CORP. British Patent 1,253,568

Porous solid carrier with 0.01-3 wt.?, Pt, 0.01-3 wt.:/o Re and 0.001 to 0.1 wt.", Ir.

A non-conductive substrate is coated with a film of rubber compounded with benzophenone and elemental. It is then exposed to actinic light in a desired pattern. The article is then sensitised and activated using PdCl,, but the unexposed areas contain free S which poisons the catalyst. This prevents the subsequent deposition of Ni.

Catalyst OLIN CORP. British Patent 1,254,204 Organic isocyanates are obtained by the reaction of nitro compounds with CO in the presence of a catalyst which includes one halide or oxide of a noble metal, including Ag and Au, but is preferably Pd, Rh, Pt or Ir.

Ruthenium Plating Bath R. MULLER-BORNIER German Offen. 2,I 141 19 Isomerisation Catalyst Ru is electroplated together with a second Pt metal SHELL INTERNATIONALE RESEARCH MIJ. N.V. (Rh, Pt or Pd) from a bath containing 0.5-50 g11 British Patent I~~559459 of Ru as the complex (NH,),,(Ru,Cl,(H,O),N Alkyliaryl hydrocarbons are isomerised by heating and 0.05-20 g:'l of the other metal. with H, in the presence of an acidic ceramic oxide

and Pd or Pt.

LABORATORY APPARATUS AND TECHNIQUE Oxygen Analyser BAILEY METER CO. U . S . Patent 3,598,711 An electrochemical cell has a ZrO, tubular electrolyte with porous Pt electrodes bonded to its inner and outer surfaces. A Pt lead from each electrode transmits the cell emf generated when the inner and outer surfaces of rhe electrolyte are in contact with gases having different O 2 contents.

JOINING

Hydrogenation Catalyst

British Patent 1,255,473 CH4 for use in nuclear reactors is obtained by the reaction of CO, with pure H, on Ru/AI,O,.

Hydroformylation Catalyst RUHRCHEMIE A.G. British Patent 1,255,537 Phenylpropanals and phenylpropanols are obtained by reacting styrene with CO and H, in the presence of Rh catalyst (e.g. Rh,O>).

Hydrocarbon Conversion Catalyst

BRITISH NUCLEAR DESIGN & CONSTRUCTION LTD.

UNIVERSAL OIL PRODUCTS CO. British Patent 1,255,544

Alloy for Brazing Powder A hydrocarbon conversion catalyst consists of a INTERNATIONAL NICKEL CO. INC. carrier material containing A1,0, and a finely U.S. Patent 3,597,194 divided crystalline aluminosilicate supporting A brazing alloy contains Ni, Pd and Zr; the alloy 0.05-1.0 wt.q/, of a Pt-group metal and 0.05- can be crushed easily and shows good adhesion 1.0 of Re. See also British Patent 1,256,000. for brazing ceramics and metals.

Catalysts British Patent 1,257,932 HETEROGENEOUS CATALYSIS OLIN 'ORP.

Organic isocyanates are obtained by reaction of Hydrogenation Catalyst nitro compounds in the gas phase with CO in the CONSOLIDATION COAL CO. presence of noble metal catalyst particularly Pd, British Patent 1,251,336 Rh, and their halides and oxides. Liquid fuel is obtained by extraction of coal with an organic solvent and hydrogenation of the extract Hydrogenation Catalyst in the presence of a Pt group metal oxide, prefer- STANDARD OIL CO. British Patent 1,259,297 ably supported on AI,O,. Phthalic acid is purified by the hydrogenation of

impurities in the presence of Pd on C. Catalyst UNIVERSAL OIL PRODUCTS CO. Hydrogenation Catalysts

Toluene is converted to C,H, and xylenes by British Patent 1,259,384 heating it in the presence of H, and a crystalline Naphthenes in a petroleum fraction are converted aluminosilicate, one of As, Sb, Bi, Se, T e or to parafiins in the presence of hydrogenation their compounds and a Group VIII metal, catalysts, preferably Pt or Pd incorporated with preferably Pt or Pd. a deionised mordenite.

British Patent 1,251,388 BRITISH PETROLEUM CO. LTD.


Disproportionation Catalyst TORAY INDUSTRIES INC. British Patent 1,260,529 Toluene is converted to C,H, and xylene in the presence of a catalyst such as Pd or Pt/A1203.

Oxidation Catalyst

British Patent 1,261,458 Olefins are converted to carbonyl compounds by reaction with O 2 and water vapour in the presence of a Pd or Rh salt adsorbed on to active C.

Reductive Amination

U.S. Patent 3,597,438 Reductive amination of aldehydes to give secondary amines is catalysed by Rh on Al,03.

Catalytic Exhaust Purifier KLEEN AIR CORP. U.S. Patent 3,598,543 An exhaust purifier consists of a chamber in the exhaust pipe containing alumina spheres which have been impregnated with a Pt salt.

Hydrocarbon Hydroprocessing

U.S. Patent 3,600,301 Hydrocarbons are hydroprocessed over a catalytic composite of a porous carrier material, a Re component, a Group VIII noble metal component and a Sn component. A specific example of a hydrocracking catalyst is a composite of a crystalline alumino-silicate, a Pt component, a Re component and a Sn component.

Hydroprocessing of Hydrocarbons

U.S. Patents 3,607,727 and 3,607,728 The hydroprocessing of hydrocarbons uses a catalytic composite of a porous carrier material, a Group VIII noble metal component and a germanium component. A specific example is a composite of a crystalline alumino-silicate, a Pt component and a Ge component, for use in hydrocracking. U.S. Patent 3,607,728 uses Pb instead of Ge.

Catalytic Purification of Terephthalic Acid MOBIL OIL CORP. U.S. Patent 3,607,921 Crude terephthalic acid is purified at elevated temperatures by contact in the presence of CO with solid particles of an adsorptive agent having substantial CO sorption capacity, e.g. Pd/C.

Catalytic Oxidation of Glucose

U.S. Patent 3,607,922 For the oxidation of glucose to gluconic or glucosaccharic acid, an aqueous solution of glucose containing Na or K carbonate or bicarbonate is contacted with an O-containing gas in a trickle column reactor in the presence of a

MITSUBISHI PETROCHEMICAL CO. LTD.

E. 1. DU PONT DE NEMOURS & CO.

UNIVERSAL OIL PRODUCTS CO.

UNIVERSAL OIL PRODUCTS CO.

JOHNSON, MATTHEY & CO. LTD.

supported Pt group metal catalyst. This corres- ponds to British Patent 1,208,101.

Production of Hydrogen Peroxide by Anthra- quinone Process F.M.C. COW. U.S. Patent 3,615,207 A catalyst for the production H,02 by the anthraquinone process contains 0.05-5')" Pd dispersed over A120, spheres. The spheres pores are less than 0.06 p. in diameter and have a BET surface area of 20-200 m'ig.

Hydrogenation Catalyst

French Patent 2,052,022 Unsaturated impurities in ethylenic gases are hydrogenated in the presence of a catalyst which is a supported mixture of Pd and V. The selectivity of the catalyst can be varied by altering the Pd : V ratio.

HCN Production

German Offen. 1,767,974 HCN and H, are produced from NH, and acrylonitrile at 1100-1400°C in the presence of a Pt catalyst.

Dehydrogenation Catalysts

Dutch Appl. 70.08,306 A supported dehydrogenation catalyst is produced by depositing a Group VIII noble metal, e.g. Pt on Al,O,or another support and then passing an inert gas containing Cd and/or Zn over the support so that elementary metal is deposited.

Activation of Supported Catalysts

Dutch Appl. 71.04723 The activity of noble Group VIII metal catalysts on porous supports is increased by treatment in three stages : oxidation, sulphiding and reduction.

Platinum Metal Catalysts

Dutch Appl. 71.05,986, German Offen. 2,121,765 Hydrocarbon conversion catalysts capable of regeneration are obtained by depositing a Pt metal and a second metal on a pretreated support and calcining the product. I n an example an A1,0, support is pretreated with Sn tartrate and calcined, Pt and additional Sn are then deposited and the product calcined a second time.

Alkyl Aromatic Compound Isomerisation

Dutch Appl. 71.07,053 The steam isomersiation of alkyl aromatic compounds is catalysed by a hydrogenating idehydro- genating metal deposited on a refractory metal acidic oxide, e.g. Pt/SiO,-Al,O,.

PRODUITS CHIMIQUES PECHINEY-ST. GOBAIN

DEUTSCHE GOLD- UND SILBER-SCHEIDEANSTALT

SHELL INTERNATIONALE RESEARCH MIJ. N.V.





Rhodium Catalyst

Dutch Appl. 71.07,603 A highly reactive Rh catalyst is obtained by contacting a Rh solution with a silica gel so that ion exchange results in the deposition of Rh on the gel surface. A suitable solution contains Rh[Cl(NHAI(OW 2.


HOMOGENEOUS CATAlLYSIS Palladium Carbouyl Complexes OLIN CORP. British Patent 1,251,744 The compound PdL(CO)X,, where L is a Lewis base, is prepared by the reaction of (for example) pyridine, quinoline or lutidine with a Pd dihalide and CO. It is a useful catalyst for the conversion of nitro compounds to organic isocyanates. British Patent 1,252,331 uses Pd(py)(SCN),.

Dimerisation Catalyst B.P. CHEMICALS LTD British Patent 1,254,776 Acrylonitrile is dimerised in the presence of a Ru compound, preferably the chloride.

Hydroformylation Catalyst

British Patent 1,255,858 Olefins are converted to aldehydes by hydroformylation with a Rh-dicarbonyl-8-diketone.

Catalysts

British Patent 1,258,045 Hydrogenation, hydroformylation and carbonylation processes using tertiary phosphine complexes with halides on psuedohalides of the Pt group metals may be improved by the use of triphenyl phosphines substituted in the para position with an electron releasing substituent.

Oxidation Catalyst

Butene is oxidised to methyl ethyl ketone in the presence of an aqueous solution containing ferrous sulphate and a Pd compound. The sulphate, nitrate or chloride are preferred.

Production of Cyclic Hydrocarbons

British Patent 1,259,973 A 1,4-cyclohexadiene is combined with a cyclo- pentadiene at elevated temperature and pressure in the presence of a Rh catalyst such as RhClL,, where L is a tertiary phosphine, arsine or stibine.

Preparation of Aromatic Isocyanates

U S . Patent 3,597,466 Organic isocyanates are made by reacting an organic nitro compound with carbon monoxide

BRITISH PETROLEUM CO. LTD

JOHNSON MATTHEY & CO. LTD.

MARUZEN OIL CO. LTD. British Patent 1,259,145

IMPERIAL CHEMICAL INDUSTRIES LTD.

OLIN MATHIESON CHEMICAL CORP.

in the presence of a halide of a noble metal and a cyanamide compound. Preferred cyanamide compounds include alkyl, dialkyl, aryl, diaryl, aralkyl and diaralkyl cyanamides. The noble metal is preferably Pd, Rh, Ir, Re, Pt.

Rhodium Polymerisation Catalyst U.S. SECRETARY OF THE ARMY U.S. Patent 3,607,850 Conjugated dienes are polymerised in aqueous emulsion by a water-soluble Rh salt or complex.

Nitrile Polymerisation

ET LUBRIFIANTS French Patent 1,603,107 Nitrile polymerisation through the C-N triple bond is catalysed by Group VIII (e.g. Pd) cyanides and unsaturated amines.

Ruthenium Carboxylate Catalysts JOHNSON, MATTHEY & CO. LTD. French Patent 2,055,059 New hydrogenation catalysts are Ru carboxylates of formula Ru,(OCOR),, where R is alkyl or aryl, and their adducts with arsines, phosphines or stibines, e.g. a Ru(I1) acetate-triphenyl phosphate adduct.

Transition Metal Catalysts

French Patent 2,055,060 New catalysts are compounds containing the cations MP+, M,(OCOR)i-i, M,(OSCR)y-k or M2(SCSR):-L, where R is alkyl or aryl and M is a transition metal, especially a Pt group metal, Mo, Cr, Cu or Re.

INSTITUT FRANCAIS DU PETROLE, DES CARBURANTS

JOHNSON, MATTHEY & CO. LTD.

FUEL CELLS AND BATTERIES Fuel Cell Electrodes

Activated fuel cell electrodes are prepared by electrodeposition of a noble metal catalyst on a solid foil or porous electrode substrate. The electrolyte is an alkali metal hydroxide solution, preferably molten alkali metal hydroxide. Pd black is a preferred noble metal catalyst and Pd or Pd-Ag alloy foils and porous sintered Ni structures are the preferred electrode substrates.

UNITED AIRCRAFT CORP. U.S. Patent 3,615,862

CHEMICAL TECHNOLOGY Solderable Stainless Steel

British Patent 1,256,147 A wet electrolytic capacitor includes a glass-to- metal seal. The metal is stainless steel which is coated first with a layer of Ni, Cr or Co and then with a layer of an alloy of Ag or Cu with one or more of the following: Au, Pd, Pt, Re or 0s.

P. R. MALLORY & CO. INC.


Photographic Composition

British Patent 1,260,722 A photosensitive medium includes a composition which on exposure to light will generate ions of a metal more noble than Ag, preferably Pd.

Flame Resistant Polymer Composition GENERAL ELECTRIC co. British Patent 1,261,637 A flame-resistant elastomer contains an organopolysiloxane, a Si hydride, filler and a Pt- containing material to give 0.5-250 parts of Pt per million parts of the organopolysiloxane.

Palladium Photographic Material EASTMAN KODAK CO. U S . Patent 3,597,206 Light sensitive Pd compounds are used in a vinyl alcoholvinyl anthranilate polymer to form a photographic material. The compounds are complexes of Pd salts and carboxylic acids.

MINNESOTA MINING & MANUFACTURING CO.

Heat Source, Suitable for Use in a Cardiac Pacemaker

U.S. Patent 3,600,586 A heat source consists of an wemitting material in a leak-tight container. The container consists of an inner sheath of T a or W and of an outer sheath of Pt.

COMMISSARIAT A L'ENERGIE ATOMIQUE

Gold Flakes

US. Patent 3,615,731 Flake Au is made by milling Au powder in a liquid hydrocarbon medium containing I-zo:~, fatty acid. The flakes are used in metallising and decorative compositions. Harder and brighter flakes are obtained by introducing up to 19.:~ Rh powder into the hydrocarbon media.

E. I. DU PONT DE NEMOURS & CO.

GLASS TECHNOLOGY Coating for Glass

British Patent 1,251,947 A glass article, e.g. the envelope of a Na-vapour discharge lamp, is provided with a transparent heat-reflecting surface film consisting of doped Ir oxide. The dopant is preferably Sn.

Manufacture of Glass Fibres

British Patents 1,259,553 and 1,259,554 Apparatus for melting and homogenising glass and drawing out glass fibres, is described. Channels and pans of Pt are included.

Platinum Coating

A material suitable for use in contact with molten

PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES LTD.

P.P.G. INDUSTRIES LTD.

CORNING GLASS WORKS U.S. Patent 3,598,635

Platinum Metals Rev., 1972, 16, ( 2 )

glass is obtained by spraying the surface of a refractory with Pt or a Pt alloy in a plasma flame, and heating the coated refractory to 1250°C.

Glass Bushing with High Emissivity Coating P.P.G. INDUSTRIES INC. US. Patent 3,600,146 Pt and Pt alloys such as those used for bushings in the manufacture of glass fibre have relatively low emissivity values. Parts of such bushings are exposed to radiant energy, and to increase the radiant heat exchange a coating of a material having a relatively high emissivity is applied.

ELECTRICAL AND ELECTRONIC ENGINEERING Ohmic Contacts for Semicondnctive Wafers HEWLETT-PACKARD CO. British Patent 1,253,092 In the manufacture of ohmic contacts, the contact area required on a Si substrate is coated with Pt and the PtSi subcontacts so formed are sputtered with LMo-Au.

Switching Device PHILIPS ELECTRONIC &ASSOCIATED INDUSTRIES LTD. British Patent 1,254,249 In the manufacture of a switching device, reed contacts of magnetic Ni-Fe alloy are coated with a layer of Au in which is dispersed at least I vol. of C, P, S, Si or metal oxide. A further layer of Ru or Rh is then applied.

Porous Anode Capacitor GENERAL ELECTRIC CO. British Patent 1,254,633 It has been found that Ti- and Ni-case capacitors enhanced with Ru are significantly superior to those enhanced with Pt, Pd or Rh.

Electrodes

British Patent 1,258,619 Pt :Ti or Pt foil on graphite is used as the anode in the production of adiponitrile by electrochemical hydrodimerisation of acrylonitrile.

Ceramic Metallising Compositions

British Patent 1,260,023 A brazeable metallising composition consists of 90-99 wt.% of at least one of Pt, Pd, Au, Ag, Rh, Ru, 0 s and Ir, and 1-10 wt."/o of a glass.

Printed Circuits

British Patent 1,260,440 A photopolymerisable composition suitable for forming patterns on inorganic dielectric substrates consists of an organic solvent, and a solid component containing 5-85 wt.O, of an organic compound of Ru, Os, Rh, Ir, Pd, Pt, Ag or Au, together with a photopolymerisable aliphatic

BADISCHE ANILIN- & SODA-FABRIK A. G.



71

compound, an organic sensitiser, an organic S compound and flux.

Anodes P.P.G. INDUSTRIES INC. British Patent 1,260,645 Anodes which may be used for electrolysis of aqueous alkali metal chloride solutions are coated with an electroconductive oxygen-containing compound which includes a Pt group metal and an alkaline earth or rare earth metal. Examples are Ca or Sr ruthenate or ruthenite.

Anodes FARBENFABRIKEN A.G. British Patent 1,261,1 14 Anodes suitable for use in the electrolytic production of olefin oxides from olefins may be made of Pt, T i coated with one or more Group VIII noble metals (especially Pt with Ir and Rh), Pt:Ta or a Pt-coated inert support.

Electrode for Cardiac Stimulator MEDTRONIC INC. U.S. Patent 3,596,662 A cardiac stimulator electrode has a pair of electrical conductors encapsulated in a flexible nonconductive plastic material, such as silicone rubber. The electrical conductors are Pt alloy coil springs with space coils.

Electroconductive Glaze

US. Patent 3,607,789 A conductive glaze consists of conductive particles in a Pb germanate glass. A suitable composition contains Au, Pt oxide and Ru oxide.

Metallising Material ALPHA METALS INC. US. Patent 3,609,105 A metallising composition for forming electrically conductive areas on dielectric materials is a mixture of 63.7",> Au, 32.3u/: Pd and 4.0": Ag.

Bismuth Titanate Film Capacitor SYLVANIA ELECTRIC PRODUCTS INC. U.S. Patent 3¶609,482 A film capacitor is made by depositing a base electrode of a Au-Pd alloy on an A1,0, substrate. A dielectric paste of a mixture of Bi titanate, a Pb borosilicate glass and a resin solution is silk screened on to the base electrode and then baked and fired. An upper electrode of Ag is deposited on the Bi titanate.

High-temperature Semiconductor

U.S. Patent 3,609,472 A contact for a semiconductor device capable of withstanding high temperature, chemical attack by silicon etchant and high oxidation atmospheres has a bimetallic layer of an alloy of Pt and Ni on the active regions. The Pt-Ni layer is coated with Pt and this is protected by a covering layer of Rh. A layer of Au is then placed on the Rh.

PRECISION ELECTRONIC COMPONENTS LTD.

T.R.W. SEMICONDUCTORS INC.

Brazeable Metallising Compositions

U.S. Patent 3,615,734 Brazeable compositions which can be fired below 14oo0C consist of 90-99oi;, noble metal(s) and I-IO?~, of a low-alkali aluminosilicate glass. The noble metals contain at least SO:;, Pt with a surface of 0.05-5 m2/g.

Oxygen Sensor

U.S. Patent 3,616,408 An oxygen solid-electrolyte cell has two longi- tudinal holes, the interiors of which are coated with porous Pt. The holes are connected to separate sources of gas to permit flow of different gases over the electrodes within the holes.

Electrolysis Electrodes

Electrolysis electrodes consist of a T i or other conducting base coated with an electroconductive oxy-compound of a Pt group metal and either a Group IIA or Group IIIA metal. A typical coating is produced by applying Rh and Mg resinaces and heating the resulting film.

Electrode for Formic Acid Combustion

German Offen. 1,671,418 An electrode for the electrochemical combustion of formic acid consists of a combination of Pt or Pc alloy plus a Group V or VI element on a conducting base.

Plasma Electrodes

German Offen. 2,025,897 Electrodes for the plasma heating of gases containing O,, e.g. for TiO, production, consist of an alloy of 10-6576 Pd, 20-657', Au and 15-50?; Ag.

E. I. DU FONT DE NEMOURS & CO.

WESTINGHOUSE ELECTRIC CORP.

P.F.G. INDUSTRIES INC. U.S. Patent 3,616,446

ROBERT BOSCH G.m.b.H.

FARBENFABRIKEN BAYER A.G.

TEMPERATURE MEASUREMENT Thermocouple S. COUDRIER British Patent 1,251,081 A thermocouple is produced by depositing separated areas of two different metals on to an insulating substrate of suitable geometry. Electric leads are provided from the metal areas to a measuring instrument. The metals used may be Pt and Pt-Rh.

Determination of Oxygen

British Patent 1,255,417 An apparatus for determination of dissolved 0, in molten steel includes a Pt : roc!& Rh-Pt thermocouple.

UNITED STATES STEEL CORP.


Documents

PLATINUM METALS REVIEW · PLATINUM METALS REVIEW VOL. 16 APRIL 1972 NO.2 Contents Platinum Catalysts in Lead-free Gasoline Production 42 Copper-Platinum 48 Alloys 48 Palladium-Silicon