Pachauri, P. C.

Rastogi, D. K.

Sharma, K. C.

Teotia, M. P.

English

NOPR

INDIAN J. CHEM., VOL. 15A, JANUARY 1977ion (it ",as usedin placeof NaHCOa to improvefiltrability of the precipitate) till a red-brown'pitate waS obtained. It was digested for halfan our on a water-bath, filtered and washedtho ughly with cold ",ater. The precipitate wasdrie by passinga streamof hot nitrogen gas. Thereac ion was carried out in the apparatus used forthe synthesis of oxinate. The dry solid was storedund r nitrogen. It is a brown amorphous solidbein slowly oxidized by atmosphericoxygen to awhi e powder.F r analysis,a weighedquantity of the compoundwas fused ",ith potassium pyrosulphate. This wasext cted with hot dilute sulphuric acid, neutralizedwit ammoniaand digestedfor 1 hy. The hydratedNb2 Iiwas filtered,ignited andweighed. Phosphoricacid was determinedin the filtrate by precipitationas agnesium ammonium phosphate [Found: Nb,37, ; P, 12·6. Nb20(P04)2.6H20requires Nb, 37,2;P, 2'4%].o idation number of niobium was determinedin t e complex by digesting a weighed quantity ofthe sample with standard potassium dichromatein M sulphuric acid for several hours and thendete mining excess of Cr(VI) by titration withstan ard Fe(II) solution. The oxidation numberof niobium was found to be +4·05 and +4·06 intwo 'independentdeterminations.T e complex is weakly paramagnetic (after dia-mag etic correction), the [.l.eff value being 0,68 BMat 3 0. The infrared spectrumshow~a strong bandat 40 cm-1due to v(Nb =0) in addition to the',1(0 ) at 3440, 8(H-0-H) at 1630 and v(P-O) at105 -1000 cm-I.T e presence of half equivalent of niobium inthe omplex in the trivalent state has been provedby t e potentiometrictitration of a known quarttityof t e compounddissolved in cold 2M hydrochloricacid (the complexis not easily solublein cold dilutesulp uric acid) with Fe(III) in a manner describedearli r6. 0·49 mole of the oxidant was consumedper ole of niobium. The EO value for the Nb(V)-Nb( II) couplehasbeenfound to be -0,230 ±0·004Vwit n =1·8. The value obtained from similarexp . iment with pure KNb(S04)2.4H20 under iden-tical condition was EO =-0,232+0'003 V. Thecom lex is thus regarded as a niobyl phosphonio-bate III) with the formula NbVO[NbIll(P04)2].6H20.T e authors express their grateful thanks toDr . Bandyopadhyay and to Dr (Miss) S. Rakshitof 0 Departmentfor their interest in the investiga-tion. Thanks are also due to the UGC, New Delhi,for nancial assistance.1.G TA, R. N. & SEN, B. K, Z. anorg.allgem.Chem.,3981973),312.2. SE , B. K, MAITI, R K, GUPTA, R N. & BANDYO-ADHYAY,P., Anal. chim.acta,81 (1976),173.EL, A. I., A textbookof quantitativeinorganicanalysisLongmans,Green,London), 1951,371.4. K STA,L. & DULAR,M., Talanta,8 (1961),265.5.CH RLES, R. G., FREISER, H., FRIEDEL, R, HILLIARD," E. & JOHNSTON, W. D., SPectrochim.Acta, 81956),1.'TA, R N. & SEN, B. K, ]. inorg. nucl. Chem.,371975),1044.Complexesof Pt(II) & Pd(II) with2-(2'-Aminoethyl)pyridineD. K. RASTOGI*,P. C. PACHAURI,K. C. SHARMA&M. P. TEOTIADepartmentof Chemistry,Meerut College,Meerut 250001Received3 March 1975; revised7 December1975;accepted6 APril 1976Square-planarPt(II) andPd(II) complexesof 2-(2'-aminoethyl)pyridine(AEP)ofthecomposition[M(AEP)X2] [M=Pt(II)orPd(II); X=CIorBr] havebeenisolatedandcharacterizedon thebasisof analytical,conduc-tall(~e,magneticmoment,electronicand IR spectraldata. Electronicspectralstudiesindicatethatthed-dbandsaremoreintensefor themixedbromocomplexascomparedtothoseforthechlorocomplexwhichcanbe ascribedto increasedligandparticipationin theoccupiedmolecularorbitallevelsderivedmainlyfromthemetald-orbitals_The IR spectralstudiesshowthatthemetalsarecoordinatedthroughthenitrogenoftheaminogroupandthepyridinenitrogenatom.THE present note describes preparation andphysico-chemical studies on the square-planarcomplexes of Pt(I1) and Pd(II) with 2-(2'-amino-ethyl)pyridine (AEP).2-(2'-Aminoethyl)pyridine, a known chelating re-agenP-3 (M-YTD grade 1614),was procured fromMidland Yorkshire Tar Distillers Ltd, England.The organic solventsand other chemicalsused wereof AR grade.Preparation of the comPlexes.'Dichloro-2(2'-amino-ethyl)pyridilept(I I) a!;d dichloro-2(2'-aminoethyl)-pyridhe Pd(I I) - Potassiumtetrachlorometalate(II)(10 mmoles)in 10 ml of water wa::treated with anaqueous solution of 2-(2'-aminoethyl)pyridine (20mmolcs)and the pH of the reactionmixture adjust-ed to ",,2,5 by adding dil. hydrochloric acid. Thereac'ion mixture Was heated on a water-bath andthe CO:1centratekept in a desiccatorfor severaldayswhen pale orange crystals of Pt(lI) complex andlight yellow crystals of Pd(I1) complex settleddown. These were filtered, washed thoroughlywith ethanol-acetoneand dried in an oven; yield50-60%.Anzlysel - Required for [Pt(C7HION2)(CI2)];C,21-65; H, 2'59; N, 7-22; CI, 18-27; Pt, 50-26%(Found: C, 21'49; H, 2'61; N, 7-15; Cl, 18-01;Pt,50'07%). Required for [Pd(C7HloN2)(C12)]:C, 28-07;H, 3·36 N, 9,35; Cl, 23,68; Pd, 35·53% (Found:C, 28-11;H, 3·29; N, 9'36; CI, 23-18;Pd, 35-58%).Dibromo-2-(2'-aminoethyl)pyridinePt(II) and di-bromo-2-('L.'-aminoethyl)pyridinePd(II) -A proceduresimilar to that used for the preparation of chlorocompounds was employed using sodium bromide(1 g) prior to the treatment of ligand. Orange-yellow crystals of Pt(lI) complex and dull-yellowcrystals of Pd(lI) complex wereobtained in 40-45%yield.AI~alyses-- Required for [Pt(C7H10N?)(Br2)]: C,17-62; H, 2·11 N, 5-83; Br, 33-50; Pt, 40-89%(Found: C, 17'59; H, 2-02; N, 5-81; Br, 33-10;Pt,40-94%). Required for [Pd(C7Hl0N2)(Br2)]:C, 21-64;*To whom all correspondenceshould be sent.NOTESH, 2·59; N, 7'21; Br, 41·15; Pd, 27'39% (Found:C, 21·62;H, 2'54; N, 6'99; Br, 40'92;Pd, 27'47%).Analyticalresultsshowthat the complexeshave1: 1 (metal-ligand) stoichiometry.Conduciancemeasurementsin N,N'-dimethylformamide(8-14ohm-Icm2mole-I)andnitromethane(4-8ohm-Icm2mole-I)showedthat the complexe&arenon-electro-lyte,>.A&expectedthe presentPt(II) and Pd(II)complexesof AEP arediamagnetic.ElectrMic spectra of [pt(C7HION2)C12]and [Pt-(C7HlON2)Br2J- The observedelectronicspectralbandsalongwith their assignmentsare given inTable 1.The first &pin-allowed-d transition(lAlg-+lA2g)in the 'ipectraof ptn2; i'i ob'iervedat 25000em-l.Tbi'i transition is reportedto undergoa shift of18000 cm-l towardshigher frequencyside in thespectraof Pt(II) complexeswith amine ligandsb~causeof spectrochemicaldifference'iin the amineand halide ligands4,5. This transiiion is observedat 34900and 32400cm-I in the presentchloroandbromo complexesre'3pectively.The 'iecondspin-allowedband due to the transition lAlg-+lEgisobservedat 29700cm-l in PtCI2;. This assignmentis supportedby magneticmomentand circulardichroism studies. The band is observedas aweak shoulderin the presentchloro and bromocomplexesat 36000 and 34150 cm-I respectively.The bandat 38200cm-l in the chlorocomplexandat 36800cm-Iin thebromocomplexmaybeduetospin-allowedtransition. The first bandappearingat 20500cm-l in the chlorocomplexandat 19000cm-I in the bromocomplexmaybe dueto a spin-forbidden (IAlc+3Eg, 3A2g)transition6. The lastband at 44500 cm-l in the chloro complexand38100 cm-l in the bromo complexis a charge-transferband (ligand-+metal).In generalthebandsin thebromocomplexoccurat lowerfrequenciesbut aremoreintensecomparedto thosefor thechlorocomplex. This maybe dueto increasedligand participation in the mole-cular orbitals derived mainly from the metald-orbitals.Electronic spectra of [Pd(C7HloN2)C12Jand [Pd-(C7HlON2)Br2J- In contrast to the spectra ofPt(II) complexes,the spectraof Pd(II) complexesdo not showthe presenceof any spin-forbiddentransition. Only spin-allowedbandsare observedat 28000, 30600cm-l for [Pd(C7HloN2)CI2Jand at25200,27050cm-l for [Pd(C7HloN2)Br2Jalongwiththetwo charge-transferbandsat 37800,48500cm-Iand 34200,46000 cm-I respectively.The detaileda'isignmentsof thebandsaregivenin Table1.An additionalcharge-transferbandobservedat48500and46000cm-lin thespectraof the presentchloroand bromocomplexesmay be due to thetransitionLa-+da* (lAlc+blEu).IR spectraof Pt(II) and Pd(II) comPlexes- ThevasNH2and vsNH2modesabsorb in the region3333-3175cm-Iin thefreeligand. Oncoordination,both the bands are considerablyloweredalongwith changesin ~NH2'~wNH2and ~rNH2modes.This indicatesthat the nitrogenof the NH2 groupservesasa coordinationcentre7.Of the IR bandsassociatedwith the pyridinering, the vsC=C,vasC=Cand vC=N vibrationshavebeenobservedasstrongbands8at 1597,1663,1471 and 1429<;m-1in the freeligand. On com-plexation,new bandsappearas follows: band-I,1615-1595em-I;band-II, 1585-1564em-I;band-III,1480-1472 cm-I and band-IV, 1435-1430 em-I.Thepositionsof thesebandsin thespectraof com-plexesaresimilarto thoseobservedfor pyridiniumion9• In addition,the shiftingof thesebandstohigherpositionsccmparedto thosefor freeligandis an indicationof coordinationof the pyridiniumnitrogento the metalatom.Four bandshave beenobservedin the far IRspectraof the freeligandat 592, 516,415 and 395em-1whichmay involveskeletalvibrationsof theframeworklo,ll.The presenceof weak bands inthe spectraof presentcomplexesin the regionTABLE1- ELECTRONICSPECTRALDATAOFSQUARE-PLANARPt(II) ANDPd(II) COMPLEXES*CompoundBandpositionAssignmentlAI aPt(C7HlON,)CI.20500IAIg_ 8E ,8A2g34900IA2g36000(wsh)lEg82Bl445l 2 ••, a IE ••3840026007Pt(C7H1oN.)Br.190l l3240015_l8",5932585d( 7 1o .)CI.8l l _l , lEg67I15153148500_blE"Pd(C7H1oN.)Br.521 l2705lg lE••2 7360blE*Energiesin em-I;interelectronicrepulsionparametersare calculatedtakingB =500 cm-l and C =3500cm-l(ref. 4).Ou(II), Pd(II) and Pt(II) complexesof tridentateSchiff base derived from 2-(2'-aminoethyl)pyridine;and salicylaldehydeor its derivatives(x-Salaep), 0-hydroxyacetophenone(Hapaep),o-hydroxypropiophe-none(Hppaep)ando-hydroxybutyrophenone(Hbpaep)havebeenobtainedas colouredcrystallinesolids. Onthe basis of analytical,magneticsusceptibility,IR andelectronic spectral data, the complexes have beenassigned square-planar geometry. IR studies showthat the metals are coordinatedthrough the nitrogenatoms of the imine group and heterocyclicring; andthe oxygenatom of a phenolicgroup.A NUMBER of planar complexesof Cu(II),Pd(II) and Pt(II) of the type (MLX) whereL is a mono-negativetridentateSchiff baseandX is a mono-negativeanion have beenreported___~~.,...,_,n 'T"L .J. '- ...l ~.:L __andagainKej)rln relflgeraTor lOT a LUUPlI:; UL u"'y".The crudeproductso obtainedwasrecrystallizedtwicefromethanolyieldingdark green,brownandred crystalsof Cu(II), Pd(II) andPt(II) complexesrespectively;yield ,...,55%.(iv) Complexesof Hbpaep were prepared.asabove employingo-hydroxybi..tyrophenone(0'025mole)and refluxingthe reactionmixtureat 60-70°for 24 hr. Concentrationof the reactionmixtureand subsequentrefriger~tionfor sevCi"aldaysresultedin the formationof complexeswhichwererecrY3tall'zed.from ethanolas paleyellow[Cu(II)~,brown [Pd(II)J and red [Pt(II)J crystalsin 40%y~W. , .•Copper(II) comPlexes- An~lyticalresults(Table1) showthe formationof 1:1 (metal-ligand)com-plexesin all the cases. _The magneticmomentvaluesin the range1·70-1·82 BM observedfor Cu(Il) .complexesare verycloseto thatexpectedforspin-onlyvalueindicating.1 •• , '~J "I i ~,_ .L~_ ~__ 1 .L .•.•• ~1_..~_".) _Complex* Colour10DqB~(em-I)(cm-I)Cr.GlY3·3H20Violet18·293466'680'50Cr.Ala3·3H20do17·95748·4.Vala·3H2O8'22973,1Leu ·3 2O9 9'4[Cr.G1Y2· H20]ClGre n1 47 2, 3l Al 2 2H ]Cl5 716[ V I2 2O]Cldo· 2[Cr.Leu2· ]CI6 434 55*All the complexesgavesatisfactoryelementalanalyses.be obtainedby heatingthe reactionmixture. Forleucir.ethereactionmixturehadtobekeptforabout70 hr with repeatedheatings.All thecomplexesi olatedin thepresentinvesti-gationare shownin Table 1. In all the casesthesolidstatereflectancespectrashowedtwoabsorptionbandsaround17,000and 23,000cm-1whichwereassignedtothetransitions4A2g-+4T2gand4A2g-+4TIg(F)respectively. Using the method describedbyFiggis5 the valuesof lODq, B and ~ have beencalculatedassumingoctahedralsymmetryfor thecomplexes,andthevaluesarelistedin Table1. Theresultsin Table1 indicatethattheaminoacidcom-plexesare weakcomplexes,yet are strongerthanthe aquo complexes.Furthermore,the valuesof~ are indicative of more iO'Jic characterin thepurple complexestha'] for the green complexes.The resultsof co;]ductivityexperiments,however,indicatethatthegreencomplexesare1:1electrolytes.This impliesthat the Cl- is presentin the outersphereof coordination.The infraredspectraof the complexesin nujolshoweda strong ba'ld ,.....,1600 cm-1 indicatingcoordinationthroughcarboxylateas well as aminogroups6. The broad absorptionaround3100-3400cm-1is dueto theoverlappingof both-NH2 aswellas HOH frequcp.cies.However,the shift in thefrequencyof the carbon-nitrogenbondat 890 cm-1(symmetricstretching)'is indicativeof coordinationthroughaminogroup. Thepeakdueto coordinatedwaterat 880cm-1(ref.8) is maskedby theaforesaid'IC-N. Howeverhigher intensity of the peak inthecomplexeshavebeenattributedto thepresenceof coordinatedwater.Amino acid complexesare strong enoughtocompetewith OH- ions. Possiblyin thebiologicalsystemstoo,aminoacidscanactasstrongerligandsfor Cr(III) and may weakenthe olationeffectofthecation. In addition,becauseof thelowstabilityof the complexes,Cr(III) canbe madebiologicallyavailableif' the activeformby complexformationwith otherliga',dsin thepresenceof aminoacids9.Furthermore,the covalentcharacterof thesecom-plexessugge~;tthat the chargeon themetalion issufficientlydelocalizedthroughcoordinationas aresultof whichthecomplexesca'1belipid solubilizedtherebyaidingthetransportof aminoacidsthroughcell membrane.Grateful thanksof the authorsare due to theCSIR, New Delhi, for financialsupport.TABLE1- Cr(III) COMPLEXESOFGLYCINE,ALANINE,VALINEAND LEUCINEINDIAN J. CHEM., VOL. 15A, JANUARY 1977332-3J2cm- may be due to vM-X (X=Cl, Br)vibra1ionswhile thosein the region318-2;0cm-1may ~dueto v'M-N (pyridine)vibrations.Th authorsare thankful to UGC, New Delhi,for fit an ialsupport.STOGI,D. K & SHARMA,K C., J. inorg.nucl. Chem.,(1974),2219.TOGI,D. K., SHARMA,K. C., DUA, S. K. & TEOTIA,. P., J. inorg. nucl. Chem.,37 (1975),685.TOGI,D. K., SHARMA,K. C. &. TEOTIA,M. P., Indian. Chem.,(in press).4. M SON,W. R. & GRAY, H. B., J. Am. chem.Soc., 90( 968), 5721.5. J rf> GENSEN, C. K., Absorption spectra and chemicalb nding (Addison-Wesley Publishing Co., Reading,.. ass), 1962,Chap. 15.6. B SCH,H. & GRAY, H. B., Inorg. Chem.,6 (1967),365.7. STOGI,D. K., ]. inorg.nucl. Chem.,34 (1972),1449.8. CO TRUP,N. B. & DALY, L. H., Introductionto infraredd Raman spectroscopy(AcademicPress, New York)1 64, 233.9. G EENWOOD,N. N. & WADE, K, J. chem.Soc., 1960,1130.10. G EEN, J. H. B., KYNASTAN, W. & PAISLEY, H. M.,pectrochim.Acta, 19 (1963),549.11. G RBI, G., OVERLAND,J. & CRAWFORD,B., J. chem.,hys.,6 (1953Y,341. .i'Co4Plexes of Cr(III) with Glycine,Alanine,I Valine & LeucineiV~ANT BRAGWAT,VANDANASHARMA& N. S. PaONIASchoollof Studies in Chemistry,Vikram University, UjjainIeceived11 March 1976; accepted5 May 1976Cr(~I) forms1:3 (metal-li~and),~reenas well aspurpl complexeswith ~lycine,alanine,valineandleuci . The coordinationthrou~hcarboxylateandamin ~roupis revealedby the IR spectraof thecompexes. The IR dataalsorevealthepresenceofcoordnatedwatermolecules.CHfOMIUM(III) is the re'centaddition to the1" t of elementswhic a biologicallyimp r antin tr ce amounts. Cr(III) is involved n glucosetOl':'~'nceandin themetabolicprocessesof fatsandprot ·ns1.Thecharacteristicpropertyof chromiumat t physiologicalpH is the olation,i.e. formingpoly~eric structuresthrough OH- bridging andits corsequentdeactivation~·3.Theextentto whicholatidnwill be inhibited,thus renderingchromiumbiologicallyavailable,dependson the complexingabi it~of the lig ndsfor chromiumagainstOH-.Such'ligandsincludethe naturallyoccurringketoacidsand the aminoacids. Partly for this reasonand artlyfor thereasonthatchromiumaidsin thetrans ortationof aminoacidsthroughthecellmem-bran 4, promptedus to study the am;no acidcom exesof Cr(III).Th complexeswereisolatedby a directreactionbetwen the hydratedmetal salt and the aminoacid n the ratio 1:3 (metal-ligand)in 50% aq.etha 01. The productthus obtainedwas washedwith!Cthanolanddriedin vaCWJ. With eachaminoaCidJreenaswellaspurplecomplexeswereobtained.The reencomplex,however,changedtopurpleonstan ·ng. A permanentpur l complex coul46Ilir I ,I ill I III ~~ ' II' III~flllil'II' I I 11111' 'I

Complexes of Pt(II) & Pd(II) with 2-(2' -Aminoethyl)pyridine

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Complexes of Pt(II) & Pd(II) with 2-(2' -Aminoethyl)pyridine

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