References1. Soon, M. L. & CHOPRA,S. L., Pak J. Sri. Res., 29 (1977), 7.2. KAUR, G., M. Sc. Thesis. Punjab Agricultural University,

• Ludhiana, (1974).3. Soon, M. L. & CHOPRA,S.L., Paper presented at the Annual

Convention of Chemists, Jaipur (1977).4. Sooo, M. L. & CHOPRA,S. L., Indian J. Tech., 13 (1975),

329.5. Soon, M. L., Pak J. Sci. Res., (Accepted).6. SANNI,S. A. & HUTCHISON,H. P., J. scient, Instrum., Part-Il

(1968), 1101.7. STOKES,R. H., J. Am. chem. Soc., 73 (1951), 3527. )Jp

8. Soon, M. L. & CHOPRA, S. L., J. Indian Chern. Soc., ..,2(1975), 98.

9. STOKES,R. H., J. Am. chem. Soc., 72 (1950), 763.10. ONSAGER,L. & Fuoss, R. M., J. phys. chem., 34 (1932).11. H.I,RNllO,H. S. & OWEN, B. B., The Physical chemistry of

electrolvte solutions,' (Reinhold, New York), 1957, 181.12. Soon, M. L., Acta ciencia Indica., 2 (1976), 110.

Metal Terphthalates & Dithioterphthalates & TheirComplexes with Ethylenediamine

C. L. SHARMA*,T. K. DE & A. K. SINGHDepartment of Chemistry, University of Roorkee.

Roorkee 247 672

Received 28 October 1978; accepted 6 March 1979

Amperometric and conductometric titrations of terphthalicand dithioterphthalic acids with Cu(ll), Ni(ll) and Co(ll) chlo-rides indicate the formation of 1:1 complexes, which have alsobeen isolated in the solid form and characterised on the basis ofanalytical and IR data. The interaction of these compounds withethylenediamine in benzene gives [Cu(en)2Jt and [M(en)31t whereM = Co(JO or Ni(lI) and t = terphthalate or dithioterphtha-late. The thermal studies on metal terphthalates and dithioter-phthalates have also been wade.

METAL terphthalates have been studied inrelation to their preparation by metathesis-".

The magnetic studies" of only copper complexes ofaliphatic and aromatic dicarboxylic (ortho substi-tuted) acids are reported in the literature. Thepresent note deals with the determination of compo-sition and structure of Cu(II) , Ni(II) and Co(II)

NOTES

complexes of terphthalic and dithioterphthalic acidsusing amperometric, conductometric, magnetic andIR studies. The results arrived at have been con-firmed by chemical analysis, DTA, TG and DTG.The interaction of these compounds with ethylene-diamine has also been studied.

Metal chlorides, terphthalic acid, ethylenediamine(en), benzene and sodium hydroxide were all AR(BDH) reagents. Dithioterphthalic acid was obtainedfrom Evans Chemetics, USA. The solutions of acidswere prepared in two equivalents of alkali and ofothers in doubly distilled water.

The solid complexes were prepared by adding equalvolumes of O.lM of the reactants. The heavyprecipitates formed were filtered, washed severaltimes with distilled water and then dried in a desic-cator over anhydrous sulphuric acid.

These compounds were treated with more than twoequivalents of ethylenediamine in benzene and themixture reftuxed for 1 hr. The resulting complexeswere filtered, washed several times with benzene an jfinally with absolute ethyl alcohol and then driedat ,....800 in an oven The insolubility oft he com-plexes in water and organic solvents precluded tnemolar conductance and molecular weight determi-nations

The amperometric titrations carried out at -1.6,-1.8 and -0.6V in the case of Cu (II), Ni(eI) andCo(II) respectively indicated the formation of 1:1complexes. This stoichiometry was also confirmedby conductometric titrations and chemical analysisof the isolated products (Table 1).

The ethylenediamine complexes are stable in solidstate or in organic solvents but dissociate in watergiving parent acids. The electronic spectra of theethylenediamine complexes were found to be thesame, indicating the formation of [Cu(en)2F+ or[M(en)3]2+where M = Co(II) or Ni(lI) , in solutionand the acids in the form of precipitates.

The IR spectra (vrnax in em-I) of metal terphtha-lates and of the acids indicated shift of v C=O,v C-O and v C-O + v O-C = 0 bands ofthe ligand appearing at /"oJ 1660, /"oJ 1410 and /"oJ 1270to 1570, 1380 and 1140 respectively in the complexes;

TABLE 1 - ANALYTICALDATA AND MAGNETIC MOMENTSOF THE COMPLEXES

Reqd.(%) Found(%) !l-eUComplexes (B.M.)

M C H M C H

[Cu (A)]a- 3H2O 24.96 37.71 2.73 24.81 37.35 2.71 1.54[Ni (A)] . 1.5H2O 23.51 38.44 2.80 23.45 38.38 2.78 2.82[Co (A)] . 2H2O 22.46 37.07 3.08 22.30 36.69 3.05 4.26[Cu (ens]A 18.28 41.43 5.75 18.20 41.06 5.71 1.89[Ni (en.IA 14.58 41.70 6.95 14.50 41.35 6.90 2.85[Co (en3)]A ·14.62 41.69 6.94 14.80 41.29 6.90 4.20[Cu(B)]2·12H20 17.28 26.11 4.35 17.20 25.89 4.31 1.45[NI(B)] . 3H.O 19.00 31.09 3.23 18.91 30.78 3.21 2.89[Co (B)] . 4H2O 18.02 29.36 3.67 18.18 29.08 3.63 4.28(Cu(en).]B 16.74 37.94 5.26 16.56 37.55 5.22 1.93[Ni (en).]B 13.50 38.64 6.44 13.38 38.38 6.37 2.84[Co (en).IB 13.55 38.62 6.43 13.77 38.24 6.36 4.24

en = CaHaN.; (A) = C.H,O, (terphthalate); and (B) = CSH.02S. (dithioterphthalate)

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rINDIAN J. CHEM., VOL., 18A, AUGUST 1979

(ii) The bands due to the presence of water appearedat 3400 and 810 and ~M-O at,..... 600 or v-- 720.

In the case of metal dithioterphthalates, the bandsat 2460 due to v S-H disappeared in the spectra ofcomplexes. The v M-S appeared at ,.....500 and theband due to the presence of water at ,.....3400.

The ethylenediamine complexes exhibited vN-Hat ,.....3280 and vC-N,..... 1140 and 1080. A strongband ,.....730 and a weak band e-- 490 may be assignedto the combined effect of ·,M-N and 'IM-Oor vM-S and vM-N bonds. The bands due tovC=O and vC-O shifted to 1650 and 1395 res-pectively. This small shift indicated that theterphthalate and dithioterphthalate ions are presentoutside the coordination sphere in the case of ethyle-nediamine complexes.

Copper terphthalate and dithioterphthalate exhibit,magnetic moments of 1.5 B. M. The decreased valuesindicate the existence of cupric complexes in thedimeric form. These values of magnetic moments(,.....1.5 B.M.) are still higher than the momentsobserved for the copper (II) alkanoates+ which maybe due to a structure in which layers of copper ionsare held together by bridging terphthalate or dithio-terphthalate ion. The magnetic moment valuesobtained for Ni (II) and Co (II) complexes lie wellwithin the range normally expected for their highspin complexes. Ethylenediamine complexes alsoshow a normal behaviour.

[Cu(C8HP4)]2.3H20 is stable up to 100° and itloses one molecule of water > 100°. The TG curveshows an intermediate stage with the composition[Cu(C8H404)] 0.5H20 in the temperature interval140°-200° and this starts losing water above 140°.The decomposition of the anhydrous form startsalmost immediately after it is formed. The DTAcurve also shows a broad endothermic peak in thetemperature region 100°-300° corresponding tothe loss of water of crystallizations. The endo-thermic peak at 360° represents fusion and indicatethe decomposition of the compound (Eq. 1). Thedecomposition to cupric oxide is shown by the DTApeak at 450°.[Cu(C8H40 4)]-+ CuO + 4C + 3CO + CH4 •• (1)

The weight of the residue left after completedecomposition corresponds to CuO and four carbonatoms, indicating oxidation of formed CO to CO2,Further the reaction is exothermic in nature as indi-cated by the peak at 440°.

The TG curve of [Cu(C8H402S2)]2' 12H20 showsthat it remains stable up to 40° and then loses watermolecules with simultaneous formation of anhydroussalt. The latter begins to decompose before all thewater has been driven off. DTA and DTG curveshow closely spaced two peaks at 130° and 160°where the rate of decomposition of the hydrated formto the anhydrous form is maximum. The anhydrousform melts at 320° as shown by a small endothermicpeak in the DTA curve and a sharp peak in the DTGcurve. The decomposition of the anhydrous form toCuO and CuS takes place in two stages as shown bythe two peaks at 400° and 460° in the DTA curve.

Similarly, [Ni(C8H404)]. 1.5H20 is stable up to60°, anhydrous form is obtained at 280° and the

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plateau due to the formation of NiO and carbonbegins at 430°. [Ni (C8H402S2)]. 3H20 remainsstable up to 100°, anhydrous form is obtained at300~ and the plateau due to the formation of NiOand NiS begins at 500°. In the case of [Co(CSH404)].

2H20, a rapid loss of water is observed from 80 to160° followed by a slower loss up to 340°. Theplateau due to the formation of CoO starts at 500°.[Co(CSH402S2)]· 4H20 remains stable up to 60°.loses three molecules of water up to 2000 and com-pletely dehydrated salt is obtained at 380°. Theplateau due to the formation of CoO and CoSstartsat 480°.

References1. FAWZY, S. G. (East Lab. E.l. dupont de Nemours & Co.)

Ind. Eng, Chem. Prod. Res. Develop., 9 (1970), 408; Clzem.Abstr., 73 (1970), 87605 e.

2. OKAMURA,HAYASHI,S., SHIODA,K. & TETSEEYA(ReesearchInstitute for Production Development) Japan, 6914,575 (CI. 25 AI) June, 1969, Appl, 7, Mar. 1964; Chem.Abstr., 72 (1970), 13376 p.

3. LEWIS,J., LIN, Y. c., ROYSTON,L. K. & THOMPSON,R. c.,J. chem. Soc., 64 (1965), 1194.

4. MARTIN, R. L. & WATERMAN,H., J. chem. Soc., (1957),2545; (1959), 1359.

A Diagnostic Criterion for Back-bonding in Organo-silicon Compounds from Diamagnetic Susceptibility

Data

R. R. GUPTADepartment of Chemistry, University of Rajasthan,

Jaipur 302 004

Received 7 August 1978; accepted 30 January 1979

A diagnostic criterion based on diamagnetic susceptibilitycontribution of silicon ion (1(SIH) is reported for back-bondingin organosilicon compounds. XSIH values calculated fromYang's method for compounds containing Si-X (X = C, 0, CI, S)bonds are reported. Values of XS1+' depend on the nature ofSi-X bond. Its value for Si-C bond (-7.54 to -7.84 X 10-'egs units) is decreased when back-bonding exists between Si andX: the extent of decrease being dependent on the extent of back-bonding between Si and X. The decrease in XSIH for a particularbond (Si-X) forms the basis of diagnosis of back-bonding in Si-Xbond.

THE recent applications of diamagnetic studiesl-5

in studying structures of organosilicon com-pounds have prompted the author to undertake thepresent work. In this note a diagnostic criterionto study the nature of bonding between silicon andX (C, 0, Cl, S) atoms is reported. Diamagneticsusceptibility contributions of silicon ion (X-S1H)calculated from Yang's method" for compoundscontaining Si-C, Si-O, Si-Cl and Si-S bondshave been used as diagnostic tool for studying back-bonding in organosilicon compounds. In Yang'smethod two shared electrons of a covalent bond areconsidered as forming a doubly charged negative