Naidu, P. R.

Rangamannar, B.

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NO T E~S1..10.90.7w01o0.50.3Prtrnene J MTAmberlite LA2o TlOAt:. THA0.1- 0.7 -0.5 -0.3log [Amin~Fig. 2 -Extraction of Co(CsO,)f- into different amines fromhydrochloric acid: dependence on amine concentrationof these amines can be monomeric. In the case ofprimene JMT, the slope is 1. The order of extrac-tion obtained was primene JMT > TIOA > THA ~LA-2.The extraction of tris(oxalato)Co(III) decreasedwith the increase in concentration of primene JMTin xylene, at fixed aqueous phase concentration(0·003N) of HCl and H2S04, The decrease in the ex-traction of the complex may be due to amineaggregation which may explain also the low slopevalue of 1 obtained in the case of prirnene JMT inearlier experiments.Somewhat similar results were obtained with O·OINH2S04 also. For TIOA and THA, a slope of 3 wasobtained. But with primene JMT and LA-2, theextraction was more than 90% even with 0'2% solu-tions of amines and hence it Was difficult to makegraphical analysis. The order of extraction wasprirnene JMT ~ LA-2> TIOA ~ THA.When log E was plotted against log amine (%)in the case of extraction with CC14, the slopes weresimilar to those obtained in the case of toluene butextraction was less.Extraction with amines using nitrobenzene as thediluent - The amine salts usually exist as ion-pairsin organic diluents of low dielectric constants. Thedegree of the ion-pair formation depends on thenature of amine salt and the organic diluent. Ifthe ion-pair formation is more in diluents havinghigh dielectric constants,. the. extraction .may alsoincrease. To study this effect, the extraction ofTABLE 1- EXTRACTIONOF TRIS(OXALATO)Co(III) INTO2% TIOA IN NITROBENZENEFROMHCI SOLUTIONSOFDIFFERENT NORMALITY[HCI] Normality of acid 100 K ExtractionNxl03x-(%)Normality of complex 31'2 40 0'74 40'231-8 60 1·476 59'62·4 80 3·34 76'93·0 100 10'6 91tris (oxalato) Co(III) was studied from different HCisolutions into TIOA in nitrobenzene. It was seenthat the equilibrium (Eq. 2) shifts completely towardsthe right hand side. The extraction into 2% TIOAin nitrobenzene, from different HCI solutions, with-out pre-equilibrating the organic layer, is given inTable 1. It can be seen that the extraction isdependent on the stoichiometric ratio of amine hydro-chloride to complex concentration (Table 1).Extraction into a mixed solvent of toluene andnitrobenzene was studied from 0·003 M HCl by varia-tion method. A plot of E against ratio of nitro-benzene to total volume was linear in the case ofTIOA and Amberlite LA-2.For THA, the extraction was similar to that forTIOA in initial stages but afterwards, the effect isnot very prominent. Nitrobenzene did not have anyeffect in the extraction with primene JMT indicatingthat nitrobenzene has less or negligible influence insystems where amines aggregate.References1. KRISHNAN, G. U. & VENKATESWARLU,K. S., Indian J.Chem., (in press).2. GRINSTEAD,R. R. & DAVIS, J. C., J. phys. Chem., 72 (1968),1630.Exchange Studies of Complexes ofCo(II) with Oximes of 2.Hydroxyacetophenone,R.esacetophenone & 5-NitroresacetophenoneB. RANGAMANNAR& P. R. i\AIDUDepartment of Chemistry. Sri Verkateswara Ur.iversityTirupatiReceived 17 March 1975; accepted 25 A:tri1 1975Isotopic exchange data of the complexes of Co(H) with2-hydroxyacetophenone oxime, resacetophenone oximeand 5-nitroresacetophenone oxime in methyl ethylketone are reported. In all the three cases the exchangeobeyed second order kinetics. The energy of activationin the case of 2-hydroxyacetophenone oxime com-plex is determined to be 16'55 kcalfmole. Differencesin exchange rates were explained in terms of substi-tuent effects.STUDY of the exchange of metal ions betweenthe complex containing the metal and the freemetal ion gives evidence on the nature of bondingin the complex. Exchange reactions of the transi-tion metal complexes with the oximes of 2-hydroxy-14-1INDIAN J. CHEM., VOL. 1M., FEBRUARY 1976aldehydes have been studied extensively', How-ever, similar studies on 2-hydroxyketoxime complexeshave not been made. This prompted us to study theisotopic exchange of Co(II) complexes of the oximesof resacetophenone and S-nitroresacetophenone.Resacetophenone oxime was prepared by themethod suggested by Dey and Sitaraman-. 2-Hy-droxyacetophenone (Fluka) was used to prepare itsoxime. S-Nitroresacetophenone oxime was preparedaccording to the method developed by Omer et al.3.Cobalt(II) solution in water was adjusted to pH7·S using acetate-borax buffer. Stoichiometricamount of the reagent to form a 1: 2 complex in~queous ethanol was added to the cobalt(II) solutionIn cold under nitrogen atmosphere. The precipitatewas allowed to settle, filtered, washed with warmwater and finally with 20% ethanol and dried at110°. The composition of the complex was ascer-tained by estimating cobalt gravimetrically. Methylethyl ketone, the solvent used in the exchange studywas purified by the method recommended byWalden4• Cobalt(II) perchlorate (BDH Analar),sodium perchlorate (E. Merck) were used as such.Solutions of cobalt(II) perchlorate labelled with6OCOand of the complexes were prepared in methylethyl ketone. Sodium perchlorate was used tomaintain the ionic strength. Predetermined volumesof the complex and labelled cobalt(II) solutions weremixed and the ionic strength of the mixture adjustedto the desired value. The mixture was kept in athermostat bath at 30·0± 0·010. The course of theexchange was followed by measuring the activityappearing in the initially inactive complex with timeafter separation from the reactants in the followingmanner. A 2 ml aliquot of the reaction mixturewas withdrawn and treated with 2 ml of water and0·5 ml of chloroform. Most of the complex wasextracted into the methyl ethyl ketone-chloroformlayer while cobalt remained in the aqueous phase.The organic phase was separated and washed withthe same volumes of water-chloroform and an ac-curately measured aliquot was transferred to acounting tube. The activity of the samples wasmeasured under the 1·3MeVphotopeak of 60COusinga gamma ray spectrometer type GRS 20B with asingle ch~nnel analyser and 3·6X 5·9 em NaI(TI)crystal WIth 1·6X 3·9 em well (Trornbay ElectronicInstruments) .The details of the procedure employed for thecalculation of the exchange rates has been reportedearlier+ The half-times and rates obtained for theexchange of cobalt between the complex and thefree cobalt (II) ion for the complexes studied aregiven in Table 1.In all the three complexes the exchange reactionwas found to obey the second order kinetics. Theenergy of activation of the exchange process wasdetermined in the case of bis-z-hydroxyacetophenoneoxime Co(II) complex from the exchange rates at 30°and 40° and the value was found to be 16·5Skcal.These ~actors indicate that the most probablemechanism for the exchange is the collision betweent~e. cobalt ion and the molecule of the complex,similar to that suggested by Calvin and Duffield forthe salicylaldoxime derivatives",142TABLE 1 - EXCHANGE DATA OF THE Co (II) COMPLEXES([Co(II] = 1·68 x 10-3NI; [complex] = 0·5 x 10-3M;[NaClO.) = 0·2M; temp. 30°}Complex Half-time ofexchange(min)Rate of theexchangereactionx 10· molelitre"! nun?Bis-Z-hydroxyacetophencneoxime Co(II)Bis-resacetophenone oximeCo(II)Bis-5-nitroresacetophenoneoxime Co(II)48·9(16·1)31·220·45·47(13·20)8·6813·lOValues in parentheses were obtained at 40°.As the rates of exchange for the three complexeswere determined under identical conditions of tempe-rature, ionic strength and solvent, the differencesin the rates of exchange observed could be attributedto the effect of substituents in the ligand. In thecase of the bis-resacetophenone oximeCo(II) complexthe hydroxyl group in the para position will decreasethe electron density due to resonance effect on thechelating nitrogen atom and hence the metal-ligand bonds in this complex would be weaker andthe cobalt is expected to exchange faster than thatcontaining unsubstituted ligand. This conclusionis in accordance with the experimental observation.Similar arguments hold good for the bis-Ssnitrores-acetophenone oxime Co(II) complex. The observedexchange rate is hence in order.References1. WEST, B., J. chem, Soc., (1952), 3115.2. DEY, B ..& SITARA~AN, M. V., Laboratory manual of organicchem%stry (S. Viswanatham, India), 1957, 264.3. OMER, R. E. & HAMILTON, C. S. J. Am. chem Sac 50.(1937), 642. ' .., 74. MULLER, R. & GRIENGL, F., Mh cu-«, 47 (1926), 88.5. RANGAMANNAR, B. & NAIDU, P. R. ]. inore. nucl Chem34 (1972). 379. '0··,6. DUFFIELD, R. B. & CALVIN. M., ] .. ~m. chem, Soc., 68.(1946), 557.Determination of Hexacyanoferrate(III)Using a Mercury ReductorL. s. A. DIKSHlTULU & DlNDI SATYANARAYANADepartment of Chemistry, And hra University, WaltairReceived 13 ]anua"y 1975; accepted 7 April 1975The method consists in reducing hexacyanoferrate(III)in O·S-l·SM hydrochloric acid in a mercury reductorand titrating the ferrate(I1) formed with cerium(IV)sulphate (in O·l-l·OM hydrochloric acid medium) usinaferroin as indicator. Amixture of hexacyanoferrate(III)an~ ferrate(II) can also be ana lysed by this methodUSlOgthe same oxidant. The method is accurate andconvenient.NU¥~RO~S methods are availablel-36 for thehtTnnetnc. de~ermination of hexacyanofer-rate(III) both In acid and alkaline media. In most

Exchange Studies of Complexes of Co(II) with Oximes of 2-Hydroxyacetophenone, Resacetophenone & 5-Nitroresacetophenone

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Exchange Studies of Complexes of Co(II) with Oximes of 2-Hydroxyacetophenone, Resacetophenone & 5-Nitroresacetophenone

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