Osmim and Rythenium Deeksha

ASSIGNMENT

CHEMISTRY OF RUTHENIUM AND OSMIUM (GROUP 8 ELEMENT)

GROUP 8 ELEMENTS

Atomic no. Element Electronic configuration

26 Iron (Fe) [Ar]3d64s2

44 Ruthenium ( Ru)

[Kr]4d75s1

76 Osmium (Os) [Xe]4f145d6 6s2

THE ELEMENTS

Ruthenium is a chemical element that has the symbol Ru and atomic number 44.

Osmium is a chemical element that has the symbol Os and atomic number 76.

The chemistry of Ru and Os bears little resemblance to that of Fe .

There is an extensive chemistry of M=O species for both the elements.

RUTHENIUM

Name, Symbol, Number Ruthenium, Ru, 44

Element category transition metals

Group, Period, Block 8, 5, d

Electron configuration [Kr] 4d7 5s1

Appearance

silvery white metallic

Electrons per shell 2, 8, 18, 15, 1

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POSITION IN PERIODIC TABLE

technetium ← Ruthenium →rhodium

•Fe↑Ru↓Os

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OSMIUM

Name, Symbol, Number osmium, Os, 76

Element category transition metals

Group, Period, Block 8, 6, d

Electron configuration [Xe] 4f14 5d6 6s2

Appearance

silvery white metallic

Electrons per shell 2, 8, 18, 32, 14, 2

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POSITION IN PERIODIC TABLE

76 rhenium ← osmium → iridium

Ru ↑Os↓H

WIKIPEDIA

OXIDATION STATES

The oxidation states of ruthenium range from +1 to +8, and -2 is known, though oxidation states of +2, +3, and +4 are most common.

Although lower oxidation states are known but these are mainly in the bonding ligands.

Cordination numbers vary from 4,5,6,7 and geomerties shown are tetrahedral,tbp,oh,distorted pentagonal bipyramidal respectively.

Oxidation states of osmium

Oxidation statesof osmium

0 Os(CO)5

+1 OsI

+2 OsI2

+3 OsBr3

+4 OsO2

+5 OsF5

+6 OsF6

+7 OsOF5

+8 OsO4

The complexes of ruthenium and osmium

HALIDESThe most important are the chlorides. Ruthenium(III) chloride

Ruthenium(III) chloride is the chemical compoundwith the formula RuCl3."Ruthenium(III) chloride" more commonly refers to the hydrate RuCl3·xH2O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a varying proportion of water of crystallization,oftenapproximating to a trihydrate, is a commonly use starting material in ruthenium chemistry.

PREPRATION

RuO4 +HCl RuCl3.nH2O

Ruthenium(II) chloride

They are obtained from in HCl solution which is reduced electrochemically or chemically using ethanol or H2/Pt black.Deep blue air sensitive solution is obtained in a reversible reaction.

Ru2(CO2Me)4 Blue solution

(not crystalline) The blue solution made by reduction have been

much used as starting material for the synthesis of Cp2Ru ,phosphine complexes,[Ru(bipy)3]2+,[RuCl6],bipyridyl complexes and Ru(acac)3.

Ru(II) Complexes

RuCl2(bipy)2,RuCl2(NMe)4 ,they have Cl at the trans position.

Ruthenium(III) chloro complexes

These range from [RuCl6]3- to [RuCl(H2O)5]2+

[RuCl6]3- + H2O [RuCl(H2O)]2- + Cl-

[RuCl(H2O)5]2+ [Ru(H2O6]3+ + Cl-

Complexes like trans [RuCl4L2] where L =imidazole; have antitumor Activity.

Ruthenium(IV) chloro complexes It forms complexes with ligands like OH and water .

[RuCl6]2- Ion is formed only in high concentrations of chloride ion by chlorine oxidation of Ru(III) chlorocomplexes.The purple brown salts are isomorphous with other [MCl6] species of Os , Ir , Pd ,Pt.

DINUCLEAR COMPLEXES These are of the type [RuX6]n-;X=Cl,Br;n=1-4;all have

octahedral geometry.When n=4,there is a mixed valence,II-III and reduced species have been observed in electrochemical studies.

Fluoroanions [ RuF6]n-;n=1-3 are well established and can be obtained by reactions like

RuCl3+MCl+F2 MRuF6

Ru +MCl2 +BrF3 MRuF6

These salts can be reduced by water and oxygen is evolved

NITROGEN LIGANDS COMPLEXES

Ru complexes with N ligands and the chemistry is very extensive.

AMMONIA COMPLEXES

The orange hexaammine [Ru(NH3)6]Cl2 is formed when ammonical solution of RuCl3( aq ) containing excess NH4Cl are reduced by Zn.

The hexaammine is a reductant

[Ru(NH3)6]Cl2 +e = [Ru(NH3)6]2+ ;E0 =0.24 V

=

Creutz-Taube Complexes The “Creutz-Taube Ion” is the metal complex with the formula

[Ru(NH3)5]2(C4H4N2)5+. This cationic species has been heavily studied in an effort to

understand the intimate details of inner sphere electron transfer, that is, how electrons move from one metal complex to another.

The ion is named after Carol Creutz, who first prepared the complex, and her thesis advisor Henry Taube who received a Nobel Prize in Chemistry for this and related discoveries on electron-transfer.

There is a series of complexes whose common feature is the presence of two or more Ru atoms bridged by bidentate ligands through which a potentially adustable degree of electron transfer can take place.

Such complexes are studied because of the information they give about the general characteristics of electron transmission through chemical systems, including spectroscopic phenomena.

Thus ion has mixed valancies,II-III ,II-II,III-III salts have been isolated .

This ion provides a model for study of intervalence transfer absorption bands characteristic of trapped valent species that correspond to the process

[Ru(II) – Ru(III)] 3+ [Ru(III) – Ru(II)] 2+

This reaction is done in the presence of light.

AROMATIC AMINE COMPLEXES

Complexes of pyridines,bipyridyls,terpydyls and other polypyridines differ considerably from that of ammonia and aliphatic amines.

They have been intensively studied because many of them have unusual properties of photo induced energy migrations,luminescence,photocatalytic reactions and water activation.

They are also involved in the construction of double helical complexes that bind to DNA and molecular rods and wires for fast electron transfer

Tris(bipyridine)ruthenium(II) chloride

Tris(bipyridine)ruthenium(II) dichloride is the chemical compound with the formula [Ru(bipy)3]Cl2. This salt is obtained as the hexahydrate, although all of the properties of interest are in the cation [Ru(bipy)3]2+, which has received much attention because of its distinctive optical properties .

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This orange crystalline salt is prepared by treating aqueous solution of ruthenium trichloride with 2,2'-bipyridine.

In this conversion, Ru(III) is reduced to Ru(II), and hypophosphorous acid is typically added as a reducing agent.

[Ru(bipy)3]2+ is an octahedral coordination complex. It is used as a sensitizer in photodriven chemical

chemical and physical processess such as photolysis of water

The bipyridyls of Ru and Os are quite similar and can occur in singly, doubly and triply reduced forms .

OTHER NITROGEN LIGANDS

It forms complexes with with nitriles ,porphyrins complexes with ligands like ammonia ,MeSO2 etc; like Ru2(porph)2 that have Ru-Ru bonds. Complexes can be both monomeric and dimeric.

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PHOSPHINE COMPLEXES

The phosphine complexes are same for both Os and Ru. They can be prepared when RuCl3.nH2O reacts with

alcohol in the presence of PR3 Sodiumborohydride can also be used as the reducing

agent . RuH2(PPh3)3 are active catalysts for hydrogenation of

C=C. Ru complexes of chiral phosphines notably BINAP- 2,2'-

bis(diphenylphosphino)-1,1'-binaphthyl are very useful for industrial hydrogenations and H-transfer hydrogenation of alkene and ketones.

BINAP

BINAP is an acronym for the organophosphorus compound 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl. This chiral ligand is widely used in asymmetric synthesis. BINAP is used in organic synthesis for enantioselective transformations catalyzed by its complexes of ruthenium ,rhodium, and palladium .

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Oxygen and sulphur ligands

There are many complexes such as [RuEDTA(H2O)]2-.Carboxylates have oxygen and sulfur bonding.carboxylates have Ru=O group. There are relatively few ruthenium complexes of sulfur ligand

Ruthenium oxo compounds RUTHENATES

1) Perruthenates ion ,RuO4- ;

RuO4 +( Prn4N) RuO4

-

The salt is soluble in organic solvents.There are vast array of oxoruthenium compounds in oxidation states from III to VII.These may have Ru=O ,-o bridge groups (which may be linear or bent)

Ruthenium oxo compounds

Ruthenium tetroxide It is a volatile ,toxic

solid ,mp=25.5 has ozone like odour.It is obtained when aq solution of RuCl3 is oxidized by KIO4 and then RuO4 swept out by a gas stream or extracted into CCl4.

It is decomposed by light and when pure it explodes above 180 0C,giving RuO2 and O2.

Aqua ions of Ru (II),(III),(IV)

There are aqua ions in II,III,IV oxidation states of which the divalent,diamagnetic,pink[Ru(H2O)]2+

is the most important as it is a useful starting material for the synthesis of numerous ruthunium complexes.

PREPRATION

RuO2 +NaIO4 RuO4 [Ru(H2O)]2+

Reduction/Pb

The lead ions are removed with sulphuric acid and [Ru(H2O)]2+ is isolated as the toluene sulfonate after ion exchange treatment .the tosylate is readily converted to triflate by ion exchange.

The 2+ ion is readily oxidized by air to yellow [Ru(H2O)]3+ is for which the reduction potential is 0.23V.

The water in [Ru(H2O)]2+ can be readily substituted by chloride ions and other anions and by neutral ligands like DMSO and MeCN.

The +2 aqua ion catalyzes several reactions in solution such as dimerization of ethylene via intermediates [Ru(C2H4)(H2O)5]2+ and [Ru(C2H4)(H2O)5]3+ and that were isolated as tosylates.

It also catalyzes polymerization of norbornenes

Ru (IV) ions are Hn[RuO6(H2O)12](4+n)+

Ruthenocene

Ruthenocene, C10H10Ru, is an organometallic compound consisting of a ruthenium ion sandwiched in between two cyclopentadiene rings. This structure can be classified as a sandwich compound and more specifically, as a metallocene.

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OSMIUM COMPLEXES

Halide complexesThe interaction of the osmate ion with aqueous HCl leads

via complex transformations to species in oxidation states III and IV some with Os=O or OH groups .The most common and useful salts for synthesis are those of hexachloroosmate(IV) ion,which are readily obtained by reducing HCl with OsO4 by Fe(II) ,the salts are brown-orange.

The ion can further be reduced to [OsCl6]3-by .The Os (V) ion is obtained by the reaction

OsO4 +SCl2+Cl2 [SCl3]+[OsCl6] Os2Cl10+SCl2 +Cl2

Oxo ,imido and nitrido compounds

The higher oxidations of both Ru and Os have a very extensive and important chemistry .

The oxo species are widely used as oxidizing agents for organic compounds.

Since M=O and M=NR are isoelectronic ,it is convenient to discuss them together and they come under nitrido chemistry.

Osmium oxo compounds

Osmium tetroxide Osmium tetroxide exists as a pale yellow-

brown crystalline solid with a odor similar to ozone.

OsO4 is volatile: it sublimes at room temperature.mp=400C

It is soluble in a wide range of organic solvents, and moderately soluble in water.

It is obtained by burning Os with oxygen .

Os + 2 O2 → OsO4

It is toxic and hahadrous to eyes. It form coloured but weak complexes with

arenes

WIKIPEDIA

It undergoes cis hydroxylation which involves [3+2] or [2+2] cycloaddition.

ANSWERS.COM

Osmium complexes with nitrogen ligands Much of the ammonia complexes resemble

that of Ru

Os

CH2 CH2

CH CH

en en

Compounds with M-M multiple bonds

Both Ru and Os form many compounds in which the multiply bonded M2n+ cores are bridged by four ligands such as carboxyl anions.

CRCR

R’NR’N O

O

Both form dinuclear porphyrin complexes such as M2(Oep)2.

Carbon monoxide derivatives RuCl3(H2O)x reacts with carbon monoxide under mild

conditions.In contrast, iron chlorides do not react with CO. CO reduces the red-brown trichloride to yellowish Ru(II) species. Specifically, exposure of an ethanol solution of RuCl3(H2O)x to 1 atm of CO gives, depending on the specific conditions, [Ru2Cl4(CO)4], [Ru2Cl4(CO)4]2-, and [RuCl3(CO)3]-. Addition of ligands (L) to such solutions gives Ru-Cl-CO-L compounds (L = PR3). Reduction of these carbonylated solutions with Zn affords the orange triangular cluster [Ru3(CO)12].

3 RuCl3·xH2O + 4.5 Zn + 12 CO (high pressure) → Ru3(CO)12 + 3 H2O + 4.5 ZnCl2

Triruthenium dodecarbonyl

Triruthenium dodecarbonyl is the chemical compound with the formula Ru3(CO)12. This orange-colored metal carbonyl cluster is a precursor to other organo-ruthenium compounds.

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Triosmium dodecarbonyl

Triosmium dodecarbonyl is a chemical compoundwith the formula Os3(CO)12. This yellow colored metal carbonyl cluster is an important precursor to organo-osmium compounds. Many of the advances in cluster chemistry have arisen from studies on derivatives of Os3(CO)12 and its lighter analogue Ru3(CO)12

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