bands at 225, 245, 300 and 345 nm and the spectraof parent phenyltin(IV) compounds used in thepresent study exhibit two bands at 220 and •......260 nm.In the spectra of the tin(IV) complexes bands appearin the ranges 2! 8-221, 244-246, 292-302 nm andone or two broad bands in the range 320-500 nrn.Slight shifts in the positions of the bands on com-plexation indicate the coordination of the ligandto tin(IV). The new band (320-500 nm range)appearing in the spectra of the complexes may beattributed to a charge-transfer transition.

The PMR spectrum of SPH in DMSO (d6) showssignals at 8 12.70, 11.67 and a multiplet between 9.10and 8.60 due to OH, NH and aromatic protonsrespectively. A marked up-field shift of the NHproton in the spectra of the adducts (8 6.32-3.75) ispresumably due to the coordination of the ligand totin(IV) through carbonyl oxygen. In the spectraof the deprotonated complexes the signal due to NHproton disappears while that of the phenolic proton(012.76) remains practically unchanged indicatingthat the deprotonation involves the removal of theNH proton through enolization of the keto group.

The authors thank Head of the Chemistry Depart-ment, Banaras Hindu University for providinglaboratory facilities. They are thankful to Sri V. N.Muley for microanalysis, to Shri R. C. P. Bipin andDr. N. P. Singh for recording the electronic and IRspectra.

References1. AGGARWAL,R. C. & RAO, D. S. S. VARA PRASADA, J.

inorg. nucl. Chem., (accepted for publication).2. AGGARWAL,R. C. & RAO, T. R., Transition met .Chem.,

2 (1977), 59.3. AGGARWAL,R. C. & RAO, T. R., Transition met. Chem.,

2 (1977), 21.4. AGGARWAL,R. C. & RAO, T. R., J. inorg . nuel. Chem.,

40 (1978), 171.5. PELIZZI, C. & PELIZZI, G., Inorg. chim, Acta, 18 (1976),

139.6. SACCONI, L. J., J. Am. chem. Soc., 75 (1953), 5434.7. GUTMAN,H. & GIST, (JR), L. A., J. org. Chem., 22 (1967),

368.8. HALLOWAY,J. H., MCQUILLAN, G. P. & Ross, D. S.,

J. chem, Soc. (A), (1971), 1935.9. VOGEL, A. I., A text book of quantitative analysis

(Longmans Green & Co., London), 1961,380, 568,569.

10. CoOK, D., J. Am. chem, Soc., 80 (1958), 49.11. SINGH, P. P. & PANDE, I. M., J. inorg . nuel. Chem.,

34 (1972), 1131.12. GEARY, W. J., Coord. chem. Rev., 7 (1971), 81.13. BRAIBANTI,A., DALLAWALLE,P., PELLlNGHELl,M. A. &

LEAPORATI,E., Inorg . Chern .• 7 (1968). 1430.14. RAo, C. N. R., Chemical applications of infrared spectro-

scopy (Academic Press, New York), 1963, 258, 265,351.

15. NAKAMOTO,K., Infrared and Raman spectra of inorganicand coordination compounds (Wiley Interscience, NewYork), 1970,211.

16. NORBURY, A. H., Adv. inorg . chem. Radiochem., 17(1975), 232.

17. TANAKA, J., Organometal. chem. uev., 5 (1970).1.18. MATSUBAYASHI,G. E., HIROSHIMA. M. & TANDKA,T.,

J. inorg . nucl, Chem., 35 (973),505.19. POLLER, R. C. & TOLEY, D. L. B., J. chem, Soc. (A),

(1967), 1578.20. CoTTON, F. A., WING, R. M. & LIMMERMAN,R. A.,

Inorg . Chem., 6 (1967), 11.21. FARONA, M. F. & GRASSELLl, J. G., Inorg . Chem., 6

(1967), 1675.

NOTES

Thermodynamics of Interaction of Thiamineortho-phosphate & Thiarninepyrophosphate with Bivalent

Metal Ions

BADAR TAQUI KHAN*, P. NAGESWARARAO &M.M. TAQUI KHAN

Department of Chemistry, Osmania University,Hyderabad 500 007

Received 6 November 1980; revised and accepted 1 January1981

Equilibrium constants fer the interaction of thlamineortho-phosphate (TOP) and thlaminepyrophosphate (TPP) with Cu(II),Ni(II), Co(II), Zn(II), Mn(II), Mg(II) and Ca(ID in 1:1 ratioof ligand to metal ion have been determined potentiometricallyat 5° and 45°C. The enthalpy and entropy changes for theformation of protonated and normal chelates have been calculatedfrom temperature coefficient data. The relatively small valuesof t,Hof and large positive values of t:,.sof indicate that theformation of the TOP and TPP chelates is mainly favoured bylarge positive entropy contribution.

THE stability constants! of metal chelates ofthiamineorthophospate(TOP) and thiaminepyro-

phosphate(TPP) at 35° and equilibrium and kineticstudies" on TPP-metal complexation have beenreported. In the present work stability constantswere determined at 5° and 45°C. The correspondingthermodynamic parameters LHJ LG'f and LS,}have also been calculated.

The experimental procedure and the methods ofcalculation have been reported earlierv". Thetitration curves of TOP and TPP in the absenceand in the presence of the metal ions under investi-gation at 5° and 45°C are similar to those at 35°C(see ref. 1).

The dissociation constants and thermodynamicparameters 'of TOP and TPP are given in Table 1.The stability constants of metal TOPjTPP complexesand the corresponding thermodynamic parametersare given in Table 2.

The stabilities decrease in the order Cu(II»Zn(II) >Ni(II»Mn(II) >Mg(II) >Ca(II) for thenormal complexes of TOP with the exception ofMn(II) and Mg(II) for the normal complexes ofTPP at 45"C. However no definite trend of stabi-lity order is observed for protonated complexes.

The stabilities of the metal chelates of TPP arehigher than those of TOP chelates. This is as perexpectation since TPP offers more potential donorsites, due to the presence of additional phosphateresidue.

For the dissociation of protons in TPP theenthalpy changes become less endothermic comparedto those of TOP due to the additional phosphateresidue. This trend is the same as observed forADP and AMp3. The enthalpy changes for thefirst dissociation in TOP and TPP is less endothermicthan that of the second dissociation. However itis difficult to explain the third proton dissociationfrom the phosphate residue on the basis of enthalpychange value.

The entropy changes for the dissociation of the

857

INDIAN J. CHEM., VOL. 20A, AUGUST 1981

first protons are positive in TOP and TPP. Thisin combination with the corresponding small posi-tive enthalpy values accounts for the high acidityof the first dissociable proton. The entropy valueis less positive in TOP than in TPP. The entropychanges are negative for the dissociation of secondand third protons, because the increased negativecharge on the ligand makes the dissociation of theseprotons difficult. The entropy of the last ionizationfrom the phosphate residue increases by 2.90 e. u.from TPP to TOP. The difference is comparable tothat observed for ATP, ADP and AMp3.

The en thai pies for the formation of the metalchelates of TOP and TPP are small exothermic, withthe exception of Mg(II) chelates, for which 6.HJis positive due to comparatively high heat of hydra-tion of Mg(II). The enthalpies of the TPP metal

chelates are, in general, more exothermic comparedto those of corresponding TOP metal complexes,with the exception of Mg(II) chelates.

The entropy values for the normal chelates ofTOP and TPP are higher compared to the values ofcorresponding protonated chelates, though thereis not much change in the enthalpy values. Theentropy values for the formation of TPP metalchelates are, in general, more positive than thecorresponding TOP chelates, may be due to thepresence of additional phosphate residue in TPPwhich offers more potential donor sites and to themore negative charge on TPP which causes theeffective release of water molecules from the metalaquo ions. On the basis of the overall observationof the 6.H'} and 6.SJ values it can be concludedthat the entropy is the principal factor which favours

TABLE1- DISSOCIATIONCONSTANTS*OFTOP ANDTPP ANDTHECORRESPONDINGTHERMODYNAMICPARAMETERS

5°

r IL = 0.1 M (KN03)]

pKapK.apK3a

2.905.396.51

1.814.866.30

pKapK.apK3a

1.935.426.50

1.604.926.52

·Standard deviation = 0.03 log units.

t:.H~ t:.G~ t:.S?(kcal/rnol) (kcal/mol) (cal deg? mol")

TOP

+3.55 ± 0.7 +2.62 ± 0.03 +2.55 ± 2.10+4.84 ± 0.7 +7.06 ± 0.03 -7.03 ± 2 10+1.94 ± 0.7 +9.17 ± 0.03 -22.74 ± 2.10

TPP

+3.34 ± 0.3 +2.33 ± 0.03 +3.17 ± 0.80+4.07 ± 0.7 +7.16 ± 0.03 -9.72 ± 2.10+1.33 ± 0.7 +9.49 ± 0.03 -25.66 ± 2.10

TABLE2- STABILITYCONSTANTSI OFMETAL-TOPAND-TPPCoMPLEXESAND THECoRRESPONDINGTHERMODYNAMICPARAMETERS

[IL = O.IM(KN03)]

5° 45° t:.H?(kcal/mol) t:.G?(kcal/mol)1 t:.sf (cal deg-1 mol.r-)Metal

ion logKJ::HL logKl logKJ::HL logKI KJ::HL Kl K~HL Kl KJ::HL KI

METAL-TOP CHELATES

corrn 2.33 3.32 2.54 3.45 -1.66- -1.84d -3.70 -5.02 +6.42 ± 2.1 +10.00 ± 2.7Ni(lT) 2.19 3.11 2.13 3.04 -0.60b -0.71b -3.10 -4.42 +7.83 ± 0.8 +11.67 ± 0.8Com) 2.12 3.20 2.29 3.09 -1.33" -O.64d -3.33 -4.50 +6.28 ± 2.1 +12.14 ± 1.8Zn(Il) 2.20 2.93 2.46 3.24 -0.85- -0.78d -3.58 -4.71 +8.58 ± 2.1 +12.36 ± 1.8Mn(ll) 1.85 2.75 2.00 2.85 -0.50b -1.15" -2.91 --4.15 +7.58 ± 0.8 +9.44 ± 3.0Mgfll) 1.34 2.15 2.00 2.62 + 1.08a + 1.30· -2.91 -3.81 +12.53±2.1 +16.07 ± 2.1Ca(!!) 1.51 2.25 2.03 2.61 -0.43" -0.291 -2.95 -3.80 +7.92 ± 0.5 +11.04 ± 0.2

METAL-TPP CHELATES

Cum) 3.79 5.12 3.85 5.34 -3.24" -2.75" -5.60 -7.77 +7.42±2.1 +15.79 ± 2.1Ni(Il) 2.53 3.64 2.36 3.53 -1.72b -l.11b -3.43 -5.14 +5.39 ± 0.8 +12.67 ± 0.8Co(II) 2.22 3.39 2.67 3.83 -10811 -3.91R -3.89 -5.57 +8.84 ± 1.2 +5.24 ± 21Zn(lI) 2.65 3.85 2.76 4.20 -0.53b -1.00b -4.02 -6.11 +10.97 ± 0.8 +16.07 ± 0.8Mnm) 2.51 3.82 2.65 4.03 -0.93b -1.24b -3.86 -5.86 +9.21 ± 0.8 +14.53 ± 1.5Mg(ll) 2.12 2.84 2.46 3.55 +1.99" +4.11" -3.58 -5.17 +17.52 ± 2.1 +29.18 ± 2.1csrrn 1.94 2.53 2.21 3.32 -0.561 -0.88d -3.22 --4.83 +8.36 ± 1.2 +12.42 ± 1.8

Standard deviations a.b.c.d.e.f.g.h.i are 0.7, 0.3. 0.2, 0.6, 1.0,0.1. 0.4, 0.5, & 0.03 respectively.

858

the formation of both protonated and normal chelatesof TOP and TPP.

One of the authors (P. N. R.) is thankful to theUGC, New Delhi, for financial support in the formof a junior research fellowship.

References

1. TAQUI KHAN, M. M. & AMARA BABU, M., I. inorg: nucl,Chem., 40 (1978), 2110.

2. KARTZ, H. B. & KUSTIN, K., Biochem, Biophys. Acta.313 (1973), 235.

3. TAQUI KHAN, M.M. & MARTELL, A.E., I.Arn. chern. Soc.,89 (1967), 5585.

Determination of Mixed Benzoic-DithiocarbamicAnhydrides Using Chloramine-T

K. K. M. YUSUFF* & M. GOPALANDepartment of Chemistry, University of Calicut,

Kerala 673 635

Received 18 August 1980; revised and accepted20 January 1981

A back titration procedure with ehloramine-T as oxidantin acidic medium is described for the estimation of mixed ben-zoic-dithiocarbamic anhydrides. The oxidation, with the con-sumption of 14 equivalents of chloramine-T per mol of the re-ductant, is quantitative in 15 min at room temperature.

THE mixed benzoic-dithiocarbamic anhydridescan be used as effective benzoylating agents'.

Recently, the mixed anhydrides have also been usedas starting materials for the synthesis of 5-coordinatemonohalogeno bis(dithiocarbamato )iron(I1I) comple-xes2 and bis(dithiocarbamato )-wdichlorodicopper(II)complexes",

These mixed anhydrides undergo decompositionon keeping, to the corresponding amides with theloss of carbon disulphide; such decompositionappears to be accelerated by light".

RzNCS2COCoH5 -+ CoHsCONR2 + CS2It was, therefore, thought worthwhile to estimate thepurity of the mixed anhydrides, for which no conve-nient titrimetric methods are available.

Chloramine-T (CAT), the sodium derivative ofN-chloro-p-toluenesulphonamide, in acidic media iscapable of breaking the S-S, N-S and C-S bonds invarious types of sulphur compounds and of oxidizingthe entire sulphur quantitatively to sulphuric acids.It has now been found that the mixed benzoic-dithio-carbamic anhydrides undergo quantitative oxidationwith CAT, and this is the basis of the method reportedin this note.

The mixed benzoic-dithiocarbamic anhydrides wereprepared and purified as described in the literature'».All other reagents used were of analytical reagentgrade purity. Just before the estimation, the mixedanhydrides were kept in a vacuum desiccator for5 min to remove any traces of carbon disulphide,which would otherwise react with CAT. A solutionof the anhydride is prepared by dissolving it (1-2mmol) in glacial acetic acid (50 ml). Chloramine-T(O.l N) and sodium thiosulphate (0.1 N) solutions

NOTES

TABLE 1- TYPICAL RESULTS OBTAINED WITH MIXED BENZOIC-DIETHYLDrrHIOCARBAMIC ANHYDRIDE AND MIXED BENZOIC-

PENTAMETHYLENEDITHIOCARBAMICANHYDRIDE

CAT consumed Equivalents of CAT(mmol) consumed/mol

reductant

Error (%)

1.4841.4861.4881.481

13.9713.9914.0113.95

-0.21-0.07+0.07+0.35

REDUCTANT TAKEN = 0.2142 mmol

3.059 14.02 . +0.14

1.391 13.94 -0.431.395 13.98 -0.141.399 14.02 +0.141.398 14.01 +0.07

REDUCTANT TAKEN = 0.2001 mmol

2.795 13.97 -0.21

were prepared and standardised using standardprocedures=",

Recommended procedure - The sample solution(5 ml) of the anhydride was taken in a stopperedconical flask, and to this was added an excess of CATsolution (0. IN, 50ml) and sulphuric acid (1M, 15 ml).The reaction mixture was allowed to stand for 15 min.Potassium iodide solution (10%, 25 ml) was added,and the liberated iodine was titrated against standardsodium thiosulphate solution. No blank correctionswere found necessary.

It was found that 14 equivalents of CAT areconsumed per mol of the anhydride. The followingreaction may be suggested for the oxidation of theanhydrides.RzNCSzCOC6Hs + 7[0] + 4H20 -+ R2NH +2H2S04 + HCOOH + C6HSCOOH

Some typical results obtained with mixed benzoic-diethyldithiocarbamic anhydride and mixed benzoic-pentamethylene-dithiocarbamic anhydride are pre-sented in Table 1. The results clearly reveal that themethod can be recommended for the micro-determi-nation of the anhydrides. The method could be mademore sensitive by employing more dilute solutions ofCAT and thiosulphate solutions.

Professors S. S. Moosath and C. G. R. Nair arethanked for their interest in this work.References

1. NAIR, P. G. & JOSHUA, C.P., Tetrahedron ie«.. 47 (1972).4785.

2. NAIR, C. G. R. & YUSUFF, K. K. ·M., Inorg . nucl, chern.u«: 11 (1975), 753.

3. NAIR, C. G. R. & YUSUFF, K. K. M., J. inorg : nucl,Chem., 39 (1977), 281.

4. TARBELL, D. S. & SCHARRER, R. P. F., J. org. Chem., 27(1962), 1972.

5. NAIR, C. G. R. JOSEPH, T. & JOSEPH, P. T .• Chemist-Analyst, 54 (1965), 111.

6. VOGEL, A. I., A text book of quantitative inorganic analysis(Longmans, London), 1961, 348.

859