Dubey, K. P.

Wazir, B. L.

English

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1NDIAN 1. CHEM., VOL. iSA, JANUARY 1911Received13 February1976; accepted24 March 1976K. P. DUBEY & B. L. WAZIRDepartment of Chemistry, University of Kash~ir, SrinagarTABLE 1 - FORMATION CONSTANTSOF 1: 1:1MIXED LIGANDCRELATES AT TEMP.=30o±1° AND fL=O'l (KNOslH1±0'084-62±0'04S'30±0'08 (ref. 1)5-48±0·09 (ref. 1)6,55±0·03 (ref. 1)6·70±0·02 (ref. 1)SystemStabilityConstantsof SomeTransition MetalComplexeswith SchiffBasesDerivedfromSalicylaldehyde& m-Aminophenolorm-AnisidineStabilityconstantsof a numberof transitionmetalcomplexeswith Schiffbasesderivedfromsalicylalde-hyde,and m-aminophenol(SMAP) or m-anisidine(SMA)havebeendeterminedin 50%ethanolat1&=0·05M(KNOa). usin~the Calvin-BjerrumpH titrationtech·niqueas modifiedby Irvin~andRossotti. Theorderof stabilitiesfor thecomplexesof first row transitionmetalsis: Cu2+>Fe2+>Ni"+>CoZ+>ZnZ+>Mn2+. Theorderof stabilitiesin the caseof someothertran-sitionmetalcomplexesis: Cr3+>UO:+>Be2+>NdH>Prs+>La3+.PACHAURI, O. P. & TANDON, J. P., Acta chim. hung.,86 (1975). 39.PACHAURI, O. P. & TANDON, J. P., ]. inorg. nucl. Chem.,37 (1975), 2321.3. PACHAURI, O. P. & TANDON, J. P., Z. Naturforsch.,30(1975), 751.4. PACHAURI, O. P. & TANDON, J. P., Mh. Chem., 107(1976), 83.5. PACHAURI, O. P. & TANDON, J. P., Bull. Akad. pol. Sci.,24 (1976), 7.6. PACHAURI, O. P. & TANDON, J. P., Bull. Akad. pol. Sci.,22 (1974), 981.7. SHARMA, G. & TANDON, J. P., Z. Naturforsch.,25 (1970), 22.8. THOMSON, L. C. & LORAAS, J. A., Inorg. Chem.,2 (1963),89.BOGUCKI, R. F. & MARTELL, A. E., J. Am. chem.Soc.,80(1958), 4170.The lower stabilitiesof the ternary derivativeswith DTPA as comparedto theanalogousCDTAor EDTA complexesmaybe explainedon thebasisof the relativestabilitiesof their binary chelates9•Due to thehigherbasicityof 1,Z-pn,its complexeshavebeenfoundto bemorestablethanthecorres-pondingen derivatives.A plot of log K~~B againstlog KMA (whereA =EDTA, CDTA, or DTPA, and B =en or 1,Z-pn)was linear indicating that the relativestabilitiesof the tClI'narycomplexesfollowthe sameorderasthe binary complexes.Th(IV)-DTP A-enTh(IV)-DTPA-1,2-pnTh(IV)-CDTA-enTh(IV)-CDT A-1,2-pnTh(IV)-EDTA-enTh(IV)-EDTA-1,2-pnthe resultspresentedin this note. The diamines --- ,- "em oyed 'Were:ethylenediamine(en), 1,2-pro-pyle ediamine (1,2-pn) and 1,3-propylenediamine(1,3pn).A stocksolutionof metalnitrate(BDH, AR) waspre redin doublydistilledwaterandstandardizedas escribedearlier6• The hydrochloridesof thedia ines (Riedel)werefirst preparedand thenre-crysallized several times. Their solutionswerepre redin doublydistilled'Waterbydirectweighing.Tri tassiumsaltofDTPA wasusedforpreparingitssoluion in doublydistilledwater. Theligand50lu- .,------.---------------tion 'Werestandardizedpotentiometricallyagainsta s andardKOH solution. The ionic strengthofall he reactionmixtureswasmaintainedconstant({L 0,1)usingO·IM potassiumnitrateandlowcon-cen ations(5X 10-3M) of theligandandmetalion.T e hydrolysisconstant(PKH) of thenormal1:1Th( V)-DTPA chelateandthe dissociationconstantsof iaminesweretakenfrom the literature? Thefor ationCOf'stantsof the mixedligandcomplexesweT calculatedby the methodssimilar10 thoseem loyedby Thompsonand Loraas8•T e potentiometrIctitration curvesof dihydro-chI idesof enand1,2-pnindicatea smalldifferencein t eir pK valuesandonlyonewell-definedinflexionat =1 (m =molesof alkali addedper moleof Referencesthe igandor metalion) in both the cases. 1hen the reactionmixture containingTh(IV) .andtheprimaryligand(DTPA) in the molarratio 2.of :1 was titrated, an inflexion at m=2 ,,,asobsrved dueto the neutralizationof two protonsfro the ligand. This indicatedthe formationofthenormalhydrated1:1 Th(IV)-DTPA chelateinthebufferregion. Furtheradditionof onemoleofalk Ii resultedin asecondbufferregion,whichmaybeasc'bedto thehydrolysisof the1:1binarychelate9•T e potentiometrictitration curves of 1:1:1Th( V)-DTPA-en and 1:1:1 Th(IV)-DTPA-l,2-pnsys msexhibitinflexionsat m=2 andm=4. Inbot the casesupto m =2,thecurvesoverlapwith 9.tha of 1:1 Th(IV)-DTPA curve indicating thefor ationof 1:1binarycomplexin theinitialstagesof t tration., Occurrenceof a secondbufferregionbet een m=2 and m=4 correspondsto theneuralization of two hydrogenions from thedia inesresultingin thestep'Wiseformationof 1:1:1mi d ligandcomplexes.T eformationof themixedligandderivativeswasfurt er supportedby drawinga compositecurve[dr n by thehorizontaladditionof the 1:1Th(IV)-DT A curveto therespectivefreesecondaryligandcur eJ,whichwasfoundtobewellabovetheexperi-me talcurvebetweenm=2andm=4in thesecases.owever,in the Th(IV)-DTPA-1,3-pn system,defil'te supportin favourof the ternarycomplexfor ation was not availablefrom the pH-metriccur es. A similarobservationwasmadein thecas~of h(IV)-EDTA or CDTA-1,3-pn system. In thesesys ms,noa preciablel weringofpH i comparisonto e theoretical ompositecurvewasn ted.comparisonof the formationconstantslistedin3abiC1indicates,thatthestabilityofmixedligandco plexesin termsof primary ligand followstheord r: EDTA >CDTA >DTPA and in termsofsecndary ligandsl,2-pn > en.S8IIHIINOTES u - - -- - -- -- - 1-.- ._,-'--' -- - ':--JIfiIIIIIfThe valuesof the protonationconstantsare: ForSMAP: logKl> 9,90;logK2' 8·05;logKs, 4,65. ForSMA. log Kl' 8·18:log K2 4·25..Theaveragenumberof ligandmoleculesattachedper metalion (n) andthe freeligandexponentpLwerecalculatedfromthetitrationcurvesof solutions(ii) and (iii). Thestepwisestabilityconstantswereevaluatedfrom the formationcurves using themethodof intrapolationat n =0·5. Thevaluesaregivenin Table 1.In all thecasesthecomplexeshydrolyseandthemetalhydroxidesprecipitatein thepH range6-10.All thecalculationswerecarriedoutbelowtherangeof the formationof metalhydroxides.From the log Kl values of complexes8H(thermodynamicstabilizationenergy)valueswerecalculatedaccordingto the methoddescribedbyGeorgeand McClures. The values are given inTable1. Thevaluesfor stabilityconstantsat 25°,and the calculatedoverall changein free energy(I:1F =-R;I' In K) for someothertransitionmetalion complexesare recordedin Table2.The data in Table 1 show that the order ofstabilitiesof first row transitionmetal complexesis as follows:Cu2T>Ni2+>C02+>Zn2+>MnllT.Except for the ferrouscomplex,this sequenceisin agreementwith the ordergivenby Mellor andMaleyt.5.Abnormallyhighstabilitiesfor theFe(lI)complexeshave been observedin many cases,particularlywith aromaticligands,e.g.riboflavin',etc. Theeffecthasbeenattributedto theresonancesta.bilizationenergyof Fe(II) complexeson coor~dinationwitha ligandhavingaromaticringsystem'.The valuesof 8H observedfor Co(II) , Ni(II) andCu(I1)complexesare alsoof the sameorderas forsomeotherligandscoordinatingthroughonenitrogenand one oxygenatom. This indicatesthat theWE reportherestability constantsof CU2T,Fe2+,Ni2T,C02+,Zn2T,Mn2+,Cr3f,UO~T,Be2T,Nd3T,PrS+andLa3+with Schiffbasesderivedfromsalicyl-aldehydesand m-aminophenol(SMAP) or m-anisidine (SMA) using the Calvin-BjerrumpHtitration techniqueas modifiedby Irving andRossotti. Sincetheligandswereinsolublein water,measurementswerecarriedout in aqueousethar.ol(50%, v/v) at {J. =0·05M (KN03).A PhilipspH-metermodelPR 9405with a glasscalomelelectrodeassemblywasusedforpH measure-ments. TheSchiffbaseswerepreparedby refluxingsalicylaldehydewith the correspondingamine. Theproductsobtainedwererecrystallizedfrom ethanoland dried in an oven at 50-60°. Solutionsofligandswerepreparedin pureethanol. The metalion solutionswerepreparedfromthecorrespondingnitrates(BDH, AR) or sulphates(BDH, AR) andwere standardized by coventional methods1.Potassiumnitrate (AR) and nitric acid wereusedto maintain constantionic strength. All otherchemicalsused were also of AR grade. All themeasurementswerecarriedout at 25°+0.1°.Thefollowingsolutions(totalvolume-50ml)weretitratedagainstcarbonate-freestandardNaOH:(i) 5 ml KNOa (0'5M)+10 ml HNOs (O,OlM)(ii) 5 ml KNOa (0'5M)+10 m1HNOa (O'OlM)+5 ml ligandsolution(O'OlM)(iii) 5 ml KNOa (0'5M) +10 ml HNOa (O'OlM)+5 mlligand solution(O'OlM) +2 ml metalsolution(0·005M)From the titration curvesof solutions(i) and(ii), fiH at differentpH valueswerecalculatedusingthemethodof Bjerrumand Calvinas modifiedbyIrving and Rossotti2.'From the experimentallydeterminedfiR-pH data, protonationconstantswere evaluatedusing Bjerru,m'shalf fi method.TABLE 1- STABILITY CONSTANTS OF DIFFERENT TRANSITION METAL IONS WITH SMAP AND SMACations log Kllog KI(38Hlog Kl8HCOMPLEXES WITH SMAPCOMPLEXES WITH SMAMnl+4'74·49·10-3·452 756'20Fel+7·155 71 ·195· 54 610'20COI+6-8023-903-27 154NiI+49'3344 3ul10'3·87 6Zn5,5, ,6TABLE 2 - STABILITY CONSTANTS AND THERMODYNAMIC DATA FOR COMPLEXES OF SMPA AND SMACations log Kllog K.log K"(3"-t::.Fl l .(3n-t :.E(kcall(kcallmole)mole)COMPLEXES WITH SMAPCOMPLEXES WITlt SMABel+9,055·10-14·1519·36'8,5512 6 9DO;+11'305'807 027-43-8 5Cr"+2·1-98'0 672La"6·40 2 0NO9Nd"5-4,0313' 0391 'P62- 57-78 ·59-~INDIAN J. CHEM., VOL. 15A, JANUARY 1977meta ions in the presentcaseare also bondedthro h onenitrogenaT'.doneoxygenatomof theligan mol~cule.This is supportedby the slightshift to higheratomicnumbersin the curve6.HL(heatof complexation)againstatomicnumberascom red to the curveof 6.HH (heatof hydrationof tal ion) againstatomicnumber. A straightline oiningMn and Zn representsthesituationinthe bsenceof crystalfieldstabilization.Th orderof stabilitiesof othertransitionmetalion mplexesi,,: Cr3+>Uo~of>Be2+>Nd3+>Pr30f >La3+.In general,SMA complexesare lessstablethanSMA complexesbecausePKn of SMA is lo~erthanpKn of SMAP.Th authorsthank Prof. C. N. Kachru, Head,Che istry Department,Kashmir University, forprovoing facilities.1. Vo EL, A. I., A textbookof quantitativeinorganicanalysisLongmas,Green,London), 1962,497,523,540.2. IR lNG,H. M. & ROSSOTTI,H. 5.,]. chem.Soc.,(1954).2904.3. GE RGE,P.&MCCLURE,D. 5., Inner orbitalsPlittinginProg.norg.Chem.,Vol. I (Interscience,NewYork), 1959,428.4. M LOR,D. P. & MALEY, L., Nature, 159 (1947),370.5. M LOR, D. P. & MALEY, L., Nature, 161 (1948)436.6. AL ERT, A., Biochem.]., 54 (1953),646.7. IR lNG,H. & WILLIAMS,R. J. P.,].chem.Soc.,(1953),3206.IStatility Constantsof Complexesof VO(II),C (II), Co(lI) & Ni(lI) with 2-Hydroxy-I-naphthaldehyde-4-m-chlor phenyl-I 3-thiosemicarbazoneII Y. N. BHATT & K. J. SHAHDtpartment of Chemistry, Saurashtra UniversityI Bhavnagarf""'''d 3 M",,' 1976,""if"d12M"y 1976Th stabilityconstantsof thecomplexesof VO(II),Cu(I , Co(II) and Ni(II) with 2-hydroxy-l-naphth-aIde de-4-m-chlorophenyl-3-thiosemicarbazonehavebeen eterminedin 70%aq.dioxane mployin~modi-fied orm of Irvin~andRossottititrationtechniqueat25±0·1°.Theorderof stabilityin termsof lo~Klis V 1+>CU2+>C02+>N{2+.ITH~OSEMICARBAZONES as ligands have not~een much studied pH-metrically. In thisnote the formationconstantsof the complexesofVO( I), Cu(II), Co(II) and Ni(II) ~ith 2-hydroxy-1-r.ahthaldehyde-4-m-chlorophenyl-3-thiosemicarba-zone (m-CINPT) employing Calvin and WilsonpH-t tration techniqueas modifiedby Irving andRoss tti in 70% aq. dioxaneare reported.m- lNPT wassynthesi.zedandcrystallizedto getanal tically purecompound.Its solutionwaspre-pare in dioxaro.e(BDH, AR) which was purifiedby t estandardmethod2.Metalnitratesusedwereof A gradeandtheirstocksolutionswerestandar-dize by gravimetricand volumetricmethods.A60TABLE 1- STABILITY CONSTANTSOF THE COMPLEXESIN70% Ag. DIOXANEMetallog Kllog K2~2ionCu2+9·54±0·059-46±0'0519· 0±0·O5Co2+·27 ··07 ·O8 34 ·0V0'83 '8'91 'Ni298 347- 6 'Philips pH-meter calibratedwith buffer solutionhaving pH 4·33and 9'1 at 25'2°±0'1°was usedfor pH measurements.All titrationswerecarriedoutat 25'2°±0'1°.Eachof the titrations ~as repeatedto get reproducibleresults. Themetal-ligandratiowasmaintained1:5.Follo~ingsolutions(totalvol. 50ml)weretitratedagainst0'2M NaOH:(i) 2 ml of O'lM HN03+5 ml of 1·0M KN03+35ml diaxane+8 ml of water.(ii) 2mlof O·lM HN03+5 mlof 1·0M KN03+5 mlof O'OIM ligand+30rulof dioxane+8mlofwater.(iii) 2 ml of O·IM HN03+5 ml of KN03+5 mlof 0·91M ligand +1 ml of O'OlM metal nitratesolutiop(iDcaseof cobalt0,5ml sclution~astaken)+30 ml of dioxane+7 rul of water.The practical proton-ligandstability constant(logpK~) fortheligandwascalculatedwith thehelpof nA valuesat differentB values(pH-meterread-ings). nA is then calculatedby the method ofIrving and Rossotti3as adoptedby ]abalpurwala.et al.4• The valueof log PK~ (=9'S2±0'05)wasthen obtainedfrom linear plotsof log nAIl - nAagainstB andusingrelation(1)P H nA )log Kl =B+log--_ ...(1I-nAFor metal-ligandstability constantsn and pIwere calculatedby the methodof ]abalpurwalaet al.4• The valuesof n are plotted againstpL.Thevaluesof logKI werecalculatedby halfintegralmethodwhilethoseof log K2 werecalculatedusingOlerup's5andleastsquaresmethods6sincetherewasnot muchd;fferencebetweenlog Kl and log K2•Theaveragestabilityconstantsaregivenin Table1. The order of stability in terms of log Kl isV02+ >CU20f>C02+'>Ni2ol'Theauthorsarethankfulto Dr K A. Thaker,Head,Departmentof Chemistry,SaurashtraUniversity,Bhavnagar,for providinglaboratoryfacilitiesandto the CSIR, New Delhi, for awardingscholarships(to Y.N.B., R.S.P. and KKP.).References1. TISLER, Z. analyt. Chem., 149 (1956),164.2. VOGEL, A. I., A textbook of practical organicchemistry(Longmans,London), 1961.177.3. IRVING,R. & ROSSOTT!,R., J. chem.Soc., (1954),2904.4. JABALPURWALA,K. E., VENKATACHALAM,K. E. & KABADI,M. B., .J. inorg. nucl. Chem.,(1964),1011.5. OLERUP, R., .rarnakloridernaskomPl e~itate(diss.) (Lind-stendtsUniversities-Bokhandel,Lund), 1944.6. IRVING, H. & ROSSOTTI,H., J. chem.Soc., (1953), 3397.

Stability Constants of Some Transition Metal Complexes with Schiff Bases Derived from Salicylaldehyde & m-Aminophenol or m-Anisidine

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Stability Constants of Some Transition Metal Complexes with Schiff Bases Derived from Salicylaldehyde & m-Aminophenol or m-Anisidine

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