INDIAN J. CHEM., VOL. 16A, JUNE 1978

t,""in

Fig. 3 - McKay plot for Cs+/H+ system on tin(IV) anti-man ate

exchange of the cations, the entropy change issmall in the solid phase, suggesting that no signi-ficant structural change occurs in tin (IV) antimonate.

The financial assistance of the CSIR, New Delhi,and the UGC, New Delhi is gratefully acknowledged.

References

1. NANCOLLAS, G. 11, & PATERSON, R., J. inorg, nucl,Chem., 22 (1961). 259.

2. HEITNER-WIRGUIN, C. & ALBU-YARON, A., J. appl.Chem., 15 (1965). 445.

3. HALLABA, E .. MIZAK, N. Z. & SALAMA, H. N., IndianJ. Chem «, 11 (1973), 580.

4. AMPHLETT, C. B., McDoNALD, L. A. & REDMAN, M. J.,J. inorg . nucl . cu-«. 6 (t 958), 220.

5. l\IATHEW, J. & TANDON, S. N., Acta Chim. (Budapest),92 (1977), 1.

6. BOYD, G. E., ADAMSON, A. W. & MYRES, L. S., J. Am.chem, Soc., 69 (1947), 2036.

7. REICHENBERG, D., J. Am. chem, soi., 75 (1953), 589.8. l\IcKAY, H., Nature iLondi, 142 (1938), 977.9. BARRER, R. M., BARTHOLOMEW, R. F. & REES, L. V. C.,

J. phys. Chem, Solids, 21 (1961), 12.10. CONWAY, D. E., GREEN, J. H. S. & REICHENBERG, D.,

Trans. Faraday Soc .. 50 (1954), 511.11. GROSHKOV, V. I., PANCHENKOV, G. M. & IVANOVA, T. V.,

Zh. fiZ. xu«: 36 (1962). 19690.12. BARRER, R. 1\I. & REES. L. V. c.. Nature (Lond.), 187

(1960). 768.13. HARNETT, D. L., Introduction to statistical me/hods

(Addison-Wesley, Massachusetts), 1970.14. MATHEW, ]. & TANDON, S. N., Can. J. cu«; 55 (1977),

3857.

526

Mossbauer Study of Fe(III) Complexesof the Derivatives of Benzoic & Acetic Acids

D. C. GUPTA & N. D. SHARMA*

Department of Physics

and

D. M. Ptmr & M. S. SAINI

Department of ChemistryKurukshetra University, Kurukshetra 132119

Received 21 September 1977; accepted 7 February 1978

Mossbauer and IR studies of monochloroferricbis-(X-benzoates) and monochloroferricbis(X -acetates)have been made at room temperature. In the former,X stands for 3,5-dinitro-, o-chloro-, p-chloro-,o-amino- and in the latter, X denotes monochloro anddlchloro. The Mossbaue r parameters indicate thatall the compounds are high spin and monomeric andFe is trivalent pentacoor dinated. Molecular weightdetermination also confirms that the complexes aremonomeric. The effective magnetic moments havealso been determined, which show that these are weakfield complexes.

FOLLOWING the work of several authorsv+ onsome mononuclear, high spin, penta coordinated

complexes of Fe(III), we thought it worth whileto prepare a series of new complexes of Fe(I1I) andstudy their structure and bonding. It is possibleto use the Mossba uer pr ra meters without muchtheoretical deta ils to elicit inforrna tion regardir.gvalency st<1te5,6, nature of the ligands, etc. From thecharacteristic rangcS of the isomer shift (IS) andthe quadrupole splitting (QS) values observed for thecomplexes, it is inferred that all the complexesprepared by us arc high spin, monomeric a ndpositive V•• indica tes that iron is tri va let:t penta-coordina ted.

Anhydrous ferric chloride (BDH) was taken ar.dana lysed before use. The organic ligands, viz.3,5-dinitrober zoic ,:cid, 0- and p-chlorobenzoic acids,benzoic acid and monochloro- and dichloroa ceticacids were of high purity a nd used r s such.Benzene WiS dried by rcfluxirg with sodium piecesand then distilled with alcohol azeotropica lly. Mole-cular weights were determined by G: llenkc mpebulliometer.

The complexes ha ve bcen prepared by the follow-in.g method: An hydrous ferric chloride wa s tr kenin a flask and dry benzene (""SO ml) wr.s addedto it. To this ligand, monochloroccetic rcid W8S

added in the mob r ra tio of 1: 2. The mixtureW3S shaken when some hea t w: s evolveeI and thesolution became wa rm. The colour of the solutionalso changed to red. The mixture solution wasrefluxed for 15-18 hr till the evolution of hydrogenchloride gas ceased. The solution w: s cooled ar.dthe solvent benzene w..s removed in vacuo r.t 60-80°.A reddish brown solid was obtained. The analysisof the compound is given in Ta ble 1.

.Prescnt address: Department of Physics, University ofMosul, Mosul (Iraq).

NOTES

TABLE 1 - CHARACTERIZATIONDATAOF THE COMPLEXES*

Sl FeCl3 Acid (g) Colour Mol. formula Fe (%) CI (%)No. (g) ------

Found (Calc.) Found (Calc.)

1 1·9526 3,5-Din itro benzoic Greyish Fe[C6H3COO(NO.)].Cl 12'13 (12-45) 8·11 (7-89)(5'104) yellow

13'51 (13-88) 17'31 (17'59)2 0'8578 o-Chlorobenzoic Reddish Fe[ o-C6H.CICOOhC1(1'655) yellow

Fe[p-C6H.CICOO.]CI 14'10 (13-88) 1741 (17'59)3 2'2910 p-Chloro benzoic Yellowish(5'191) brown

10'02 (9'77)4 1-5654 o-Aminobenzoic Blackish Fe[ o-C6H.NH.COO].Cl 15·11 (15,40)(3-452) brown

10'76 (10'64)5 1'8230 Benzoic (3'452) Brownish Fe[CeH.COO].Cl 16'70 (16'79)yellow

19'78 (19'78) 37·58 (38'24)6 2·5800 Monochloroacetic Reddish Fe[CH.CICOO] 2Cl(3·076) brown

7 2'1018 Dichloroacetic Yellowish Fe[CHCl.COO].Cl 15'58 (16,11) 50·49 (50'08)

*Time of refluxing for SI Nos. 1-6 is 15-18 hr and for SI No.7 is 25-28 hr.

TABLE 2- M6sSBAUERPARAMETERSOF THE COMPLEXES

IS (3) QS (6.E.) (Peak)LH3 (Peak)RHS(relative to Fe) mm/sec

Relativemm/sec (± 0'04) FWHM Relative FWHM(± 0'04) mmjsec depth mm/sec depth

(± 0'04) (± 0'04)

0·36 0'95 0·80 0·028 0'70 0'0240'41 1·26 0'63 0'032 0'50 0'0270'29 1'63 0'63 0·031 0'51 0'0250'54 1'76 1'00 0·032 0'76 0'0280'45 1'70 1'00 0·039 0'63 0·0340'41 1'51 0'75 0·014 0'50 0'0100'35 1'64 1'20 0'065 0'63 0·037

Compd*

1234567

·Sl Nos. refer to the compounds with ligands as given in Table 1.

Similarly, complexes with dichloroacetic acid.3,5-dinitrobenzoic acid, 0- and p-chlorober zoic acids.o-aminobenzoic acid and benzoic acid were prepared.The experimental conditions for the preparationof the complexes with these ligands are given inTable 1.

The infrared spectra were recorded in nujolon a Beckman IR-20 spectrophotometer for all thecomplexes.

M6ssbauer spectra of all the complexes weretaken on a constant acceleration electromechanicaltransducer drive set-up in transmission geometrywith ND-512 channel analyser. The source usedwas a 5 mCi 57CO in stainless steel matrix. Thecounts accumulated at each channel were 105 ormore.

The magnetic susceptibility was determined atroom temperature using the Gouy method", Theexperimental set-up was calibrated with FeS04 andCuS04 salts.

The general formula for the complexes is Fe(L)2Cl,where L stands for the ligands. The molecularweight of the complexes was also determined andthe complexes were found to be monomeric innature.

The infrared spectra of the complexes indicatethat vCO is lowered by 20-30 crrr? suggestingcoordination of iron to the carbonyl oxygen. How-ever. in the case of a-aminobenzoic acid, the vCO

shifts to higher frequency region (~v = 30 cm+)probably because of an increase in electron der.sityaround nitrogen atom resultirg in M-N bondformation rather than M-O bond formation.

The Mossbauer spectra recorded at room tem-perature and the computed partmeters, given inTable 2, indicate that the compounds are high spin.The presence of doublet asymmetry in all thecomplexes suggests a positive V" which in turnindicates that iron is pentacoordina ted. It wr.spossible to identify the lines in the que drupolesplitting of these complexes to 7t or rr transitionwithout resorting to the study of angular depen-dence of ratios of the areas in single crystalsv".The samples being polycrystalline, the Mossbauerspectra were also recorded in an externalfield magnetic of strength 15 ROe. This onlyin slight resulted broadening of the respectivedoublets",

An ana lysis=" of broadening of linewidth showstha t the left-hrr.d line in the spectrum correspondsto 3/2--*1/2 transition, resultir g in positive V"confirming tha t the ccmpour.ds are pente coordir a ted.The positive V" is explained only on the basis ofa square pyramidal array of ligands which havemore negative charge in the x-y plane than in thepyramidal axis. Thus, it W2S possible to proposesquare pyramidal structure for all the complexeswhich is shown in Fig. 1.

527

INDIAN J. CHEM., VOL. 16A, JUNE 1978

.0• CIo Fo

R'C=======-j..Fig. 1 - Proposed square pyramidal structure for all thecomplexes, where R stands for 3,S-(N02)2C.H3' o-CIC.H.,

P-ClC.H., o-NH2C.H., C.H., CICH2 and Cl2CH

The possibility of doublet asymmetry arisirgdue to acciden tal preferred crystal orientation inthese complexes has been excluded.

The isomer shift, a-va lues of ber zoic a r.d ; ceticacid complexes fall in the rar-ge (0·29± 0·04) a r.d(0·54 ± 0·04) mm/sec and the quadrupole splittir.g,!lEQ-v< lues are in the rar ge from (0·95 ± 0·04) to(1'76± 0·04) mm/sec suggesting that the compoundsore high spii." ar.d the iron is trivalent. However,the large difference in the II-values of monochloro-ferricbis(3,5-dinitrober.zoa tel and monochloroferric-bis(o-a mir.obei zot.te) may probe bly arise because thenitro group is much more electronegative than theamino group. The difference in the 6.EQ-values ofmonochloroferricbis(3,5-dinitrobenzoa tel and mOI~O-chloroferricbisfc-i.mir.obar zoa te) compounds may bea ttributed to the varying electric field gradient(EFG) of the iron atom in the two cases. Therel« tive depths of both left-hand and right-h<lr.dpeaks of the Mossba uer spectra for a 11the complexesr.rc clso listed in T, ble 2 a long with full width athalf maximum (FWHM). Much broadened quadru-pole doublet in the case of monochloroferricbis-(o-aminobe..r zoate) may be due to the preser.ce ofthe, mino group at the ortho position which ca usesdistortion in the structure.

The effective magnetic moments, (l-efl at roomtemperature for different Fe(III) complexes werefound to be in the range from 5·88 to 6·07 BM.This is in ; greement with the observa tior.s ofGerloch et al.lo ar.d suggests that the environmentof the iron a tom in a ll the complexes is in we a k field.

The authors are thankful to Kurukshetra Univer-sity, Kurukshetra, for providing facilities for carryingout this work. Two of the authors (D.C.G. andM.S.S.) are grateful to UGC and CSIR, New Delhi,for the fi. ancial support in the form of senior andjunior research fellowships respectively.

References

1. MATHUR, H. B. & GUPTA, M. P., Indian J. cte«; 5(1967), 208.

2. BANCROFT,G. M., MADDOCK,A. G. & RANDL, R. P.,J. chem; Soc. (A). (1968), 2939.

3. Cox, M., cu»: COmmun., (1969), 183.4. MAHESH, K., SHARMA,N. D. & PURT, D. M., Indian

J. Chem., 14A (1976), 338.S. MAY, L., Ado. Chem., Series No. 68 (American Chemical

Society, Washington), 1967.6. REIFF, 'w. M., M.E. Methodology, Vol. 7, edited by

I. J. Gruvcrrnan (Plenum Press, London), 1971, 222.7. FIGGIS, B. N. & LEWIS, J., Modern coordination chemis-

try, edited by J. Lewis & R. G. Wilkins (Interscience,New York). 1967, 400.

528

8. RUBY, R. L. & FLINN, P. A., Rev. mod. Phys., 36 (1964).351.

9. COLLINS,R. L., ]. chem. Phyg., 42 (1965), 1072.10. GERLOCH,M., LEWIS, J., MABBS, F. E. & RICHARDS,A.,

J. chem, Soc. (A), (1968), 112.

Temperature Dependence of Frequency ofOscillation of Belusov-Zhabotinskii Reaction

Using Different Organic Substrates

R. P. RASTOGI, J OKHOORAM SHUKLA&ANIL KUMAR SINGH

Chemistry Department, University of GorakhpurGorakhpur 273001

Received 17 April 1978

The energy of activation of frequency of oscillationin B-Z-reagent having different organic substrates hasbeen estimated. It is found that these are different fordifferent organic substrates showing that the fre-quency-controlling reaction steps are different in diffe-rent cases. An explanation has been advanced.

IT has been observed by Rastogi and coworkers-that the logarithm of the frequency of Mn2+

catalysed oscillatory reaction between malonic acidand bromate ion depends inversely on reciprocalof the absolute temperature. This observationhas been subsequently confirmed by Blandamerand Morris for cerium catalysed oscillatory reaction",Quite recently Blandamer and Roberts" have esti-mated the activation energy of oscillation frequencyand their computer calculations indicate that thefrequency is controlled to a significant extent bythe rate of reaction between bromide and bromateions to form HOBr and HBr02• We report in thiscommunication energies of activation of frequencyof oscillation for Belusov-Zhabotinskii reaction in-volving different organic substrates for the sakeof comparison. This is expected to give an insightin the difference in mechanism, if any.

Least square values of energy of activation ofoscillation frequency for different reactions wereestimated using the available experimental data.The values are recorded in Table 1.

The values of energy of activation for malic acidsystem is in excellent agreement with that f?r. theoxidation of malonic acid by bromate ions in acidifiedsolution containing cerium ions, viz. 63·8 ± 1·3 kJmol-l as reported by Blandamer and Roberts. Inother cases, there is deviation. This shows thatin the former two cases the mechanism of oscillationmay be similar and the reaction between oxybrominespecies may be more significant but the results forthe last three systems in Table 1 show that theorganic substrate considerably influences the energyof activation and the nature of intermediates mustbe playing an important role in the overall sequenceand final frequency as is also suggested by computeranalysis.

The frequency v would be a function of the rateconstants of individual steps and the concentration