Ghosh, S. P.

Prasad, K. M.

English

NOPR

II!IiIIiIndiantr0urnslaf ChemistryVol. 1¥, July 1977,pp.630-632iIIiII Molybdenum(lII)IComplexeswith UnidentateNitrogenDonorsS. P. GHOSHDepartmentof Chemistry,PatnaUniversity,Patna800005andK. M. PRASADDepartmentof Chemistry,H. D. Jain College,Arrah802301Received 18 October 1976;accepted 9 March 1977Complexesof stoichiometry[MoX3L3] (X =CI-, Br- or NCS- and L =J3-picoline,'Y-picoline,I piperidine or benzimidazole)have been prepared by the interaction of (NH4)2[MoClsH20],(NH4)2[MoBr5H20]and (NH4)3[Mo(NCS).]with the bases. The complexesare characterizedby magneticand spectralmeasurements.T:fIE study of the chemistryof molybdenum-(III) is becomingincreasingly importantIlbecauseof the suggestionsthat Mo(III) maybeiintolvedincatalysisbynitrogenase1andmolybdo-enzY$es2 and in the reductionof dinitrogeninmode)experimentsa.Severalcomplexesof Mo(III)with j unidentatenitrogen donors of composition[MoqaLaJ (L =py, MeCN Or PhCN) have beenpreParedby exchangereactionsof Ka[MoCI6Jwithorgarpcligands4,5. Allen and coworkers6obtaineda ser*sof complexes,[MoBraLaJ(L =MeCN,EtCNor !tCN), by treating MoBra with an excessof appropriatenitrilein a sealedtubeat 150°. WehaveIpreviouslyreportedthe preparation,spectraland tmagneticpropertiesof Mo(III) with SOmebiden~atenitrogendonors7• In the presentpaperpreparationand characterizationof the complexesof Mp(III) with someunidentatenitrogendonorheter~cyc1icbasesand benzimidazoleare reported.IMat~rialsand MethodsAmJuoniumsaltsofpentachloroaquomolybdate(III),pent~bromoaquomolybdate(III),and hexisothio-cyan tomolybdate(III)were prepared by theelectmlyticreductionas describedin literatures-1o.Alli reactionswerecarriedout in pure and drynitrogenatmosphere.But thecomplexesof Mo(III)with ipicolineswerepreparedin an ordinaryatmo-sphe~eas describedby Jonassenand Bailin4 in theprep~rationof [MoCla(pyhJ.Tr~hloro-tris(Y-picoline)molybdenum(III)- (NH4k[MoC15H20J(2 g) was refluxed with freshlydistiijedY-picoline(15 ml) for 4 hr. At the endof th~reactionandon cooling,a yellowprecipitatein darkbrownsolutionwasobserved.Theproductswereipouredin distilledwater (75ml) and stirredthorq'ughlyfor 2 hr. The yellow residue wasfilter¢d,washedwith wateranddriedin vacuooverKoHl (Found: Mo, 20'00; N, 8'88; Cl, 22'30.[MoC)a(Y-pichJrequires Mo, 19·94; N,8'87; c1,22-111%).Tr~chloro-tris(~-picoline)molybdenum(III) - (NH4k[MoC)5H20J(0'85 g) was refluxed with freshlyI630distilled~-picoline(8ml)for6hr. Like thepreviousexperimentthe reaction products were stirredthoroughlywith distilledwater. The yellowsolidwasfiltered,washedwith wateranddried in vaC',toover KOH (Found: Mo, 19'86;N, 8'76;Cl, 22·08.[MoCla(~-picJaJrequires Mo, 19'94; N, 8'87;c1, 22·11%).Tribromo- tris(Y-picoline)molybdenum(III) - Thiscompoundwas preparedby refluxingammoniumpentabromoaquomolybdate(III)with Y-pieolineandusing the conditionsidentical to thosedescribedabove (Found: Mo, 15'70; N, 6'78; Br, 39·15.[MoBr3(Y-pichJrequiresMo, 19·61;N, 6'83; Br,39·02%).Tribromo- tris(~..Picoline)molybdenum(III)- Thiscompoundwaspreparedas abovefromthe ammo-nium pentabromoaquomolybdate(III)and freshlydistilled~-pieoline(Found:Mo, 15'67;N, 6'77;Br,39·16;[MoBr3(~-pie)aJrequiresMo, 15·61;N, 6'83;Br, 39·02%).Tribromo-tris(pij)eridine)molybdenum(II1)- Ammo-nium pentabromoaquomolybdate(III)(1 g) waskeptin a 125ml flaskunderdrynitrogenandabout20 ml piperidinedistilledinto it. It was stirredthoroughlyand filtered. The brownishyellowfil-tratewaskept in vacuooverCone.H2S04for 24hr.The pale yellow solid was filtered,washedwithpetroleumetheranddriedin vacuooverKOH/CaC12(Found:Mo, 16·09;N, 7·14;Br, 40,58.[MoBra(pip)3JrequiresMo, 16·24;N, 7,11;Br, 40·61%).Triisothiocyanato- tris(Y - Picoline)molybdenum(III)- A mixture of Y-picoline (10 ml) and(NH4MMo(NCS)6J(0·5g) wasstirredfor 3hr. Ondilution with largevolumeof water,a fine yellowsolidwasseparatedfromthereactionmixture. Thesolidwaswashedwithwateranddried in vacuooverKOH/CaCI2(Found:Mo,17·52;N, 15'45.[Mo(NCSk(Y-pielaJrequiresMo, 17'48;N, 15·30%).Triisothiocyanato- tris(~- picoline)molybdenum(III)- This compoundwas preparedas aboveby thereactionof ~-pico1ineand(NH4MMo(NCS)6J (Found:Mo, 17·56;N, 15·38. [Mo(NCSh(~pichJrequiresMo, 17·48;N, 15·30%).GHOSH & PRASAD: Mo(UI) COMPLEXES WITH NITROGEN DONORSTriisothiocyanato- tris(piPeridine)molybdenum(III)- (NH4MMo(NCS)6J(0'8g) was allowedto reactwith piperidine(15ml) in dry nitrogenatmospherefor 8 hr with constantstirring. The yellowishredsolutionwasfilteredand the filtratekept in vacuooverconc.H2S04 for 24hr. The separatedyellowsolid was filtered,washedwith minimumvolumeof water-ethanol(2:1) and dried in vacuo overKOH/CaC12(Found: Mo, 18'18;N, 16·10. [Mo-(NCSJa(piphJrequiresMo, 18'28;N, 16'00%).Triisothiocyanato-tris(benzim,idazole)m,olybdenum(III)- A solutionof0·5g (1mole)ammoniumhexisothio-cyanatomolybdate(III)in 15mlmeth2nolwasstirredthoroughlywith 0,36g (3moles)benzimidazoledis-solvedin 10mlmethanolundernitrogenatmosphere.Whendeepeningof yellowcolourtookplace,it wasfilteredand the filtratedilutedwith largevolumeof wateruntil a deepyellowsolid separated.Itwas filtered,washedwith water-ethanol(1:1)anddriedin vacuooverKOH/CaC12(Found:Mo, 15'42;N, 20·22.[Mo(NCSh(BzH)aJrequiresMo, 15·38;N, 20'19%).Physical measurements- Conductivity measure-mentsweremadewith WTW conductivitymeter,typeLBR. Magneticsusceptibilitiesweremeasuredon a Gouymagneticbalanceat roomtemperature;diam3.gneticorrectionsweremadeusing Pascal'sconstantsll. The electronicabsorptionspectraofthe solutionsweremeasuredon a HilgerandWattsUvispekspectrophotometermodelNo. H 700withsilicaprism. A Hilger-Uvispekstandardreflectanceattachmentwas used to measurethe reflectancespectra,with MgCOaasreference.IR spectrawererecordedon Perkin-Elmer 237and 621recordingspectrophotometerswith samplesmountedin KBrdiscs.ResultsandDiscussionReactionof ~-orY-picolinewith ammoniumsaltsof pentachloroaquomolybdate(III)or pentabromo-aquomolybdate(III)at reflux temperatureleadsto the isolationof heterocomp1exesof composition[MoXaLaJ(X =Cl-or Br- andL =~-orY-picoline).Ammonium hexisothiocyanatomolybdate(III)alsoreactswith ~- and Y-picolines,on stirring in thecold with appropriateamountof ligandsto formcomplexes[Mo(NCS>a(~-pic)aJand[Mo(NCSJa(Y-pichJrespectively.oc-Picolinedoesnot reactsimilarly,probablybe-cause of steric hindrance causedby 2-methylsubstituent. Piperidine reacts with (NH4)2 [Mo-Br5H20J under nitrogenatmosphereand (NH4)a-[Mo(NCS)6Jin cold forming [MoXa(pip)a](X =Br-or NCS-). But (NH4MMoC15H20J fails to formcomplexofdefinitecompositionwi'hpiperidineowingto rapid hydrolysis of ammoniumpentachloro-aquomolybdate(III).At the reflux temperaturepentabromoaquomolybdate(III)and hexisothio-cyanatomolybdate(III)are also hydrolysedwhichmaybe dueto greaterbasicityof piperidine(pKa=11-13).Benzimidazole(BzH =C7H6N2) replacesthreeofthe six thiocyanategroupsin ammoniumhexiso-thiocyanatomolybdate(III)in methanolunderpuri-fied nitrogen atmosphere,forming a complex[Mo(NCS)a(BzH)a].The tris-benzimidazoleligatedcomplexis insolublein waterand is precipitatedasadeepyellowcrystallinesolidfromthemethanolicreactionmixture on dilution with water.All thesecomplexesarefairlystablein air andaresparinglysolublein water. An aqueoususpensionof thepiperidinecomplexesof Mo(III) is graduallyhydrolysedgiving a brownishblack precipitateofindefinitecomposition.The complexesareslightlysolublein ethanolandacetonebut fairly solubleinmethanol. The methanolicsolutionsof the COm-plexes[MoXaLaJare almostnon-conductingindi-cating the non-electrolyticnature of thesecom-plexes.The effectivemagneticmomentvalues of thecomplexesat roomtemperature(3000K)are in therange3'7-3,85BM (Table 1) as expectedfor thespin only valuefor a tigconfigurationl2,suggestingan octahedralarrangementof the ligandmoleculesaroundMo(III) ions.The tris-ligatedcomplexesof picolines,piperidineandbenzimidazolexhibitanintensechargetransferband near 24000-27000cm-l (Table 1). The d-dtransitionsof the complexesof the type [MoXaLaJare probably obsc'uredby extendedtail of thechargetransferband.The IR spectraof [MoXa(Y-pic)a](X =Cl-, Br-or NCS-)exhibita bandat ,..."1020-1025cm-lwhichis absentin the freeY-picolineandis attributedtothe shift of symmetricring breathingmode(997cm-I)of the freeligand. Graddonand coworkersiaobservedthe samepatternof shifts in octahedralcomplexesof cobalt(II) with Y-picoline. The shiftof a strongbandat 1608cm-lin Y-picolineand1580cm-Iin ~-picolineto thehigherfrequency,1615-1628cm-Iand 1602-1615cm-Irespectivelyaredignosticof coordinationof Y- and ~-picolines.In the Caseof [MoXa(piP)aJ(X =Br- or NCS-)theabsorptionbandsat 1445-1450cm-Iand866-870cm-Ican be assigned-N-H asymmetricand N-Hdeformationfrequenciesrespectively.When Com-paredwith -N-H asymmetric(1440cm-I)and N-Hdeformation(860cm-I)bandsof the freepiperidinewefindashifttohigherfrequenciesin boththebandswhich is in agreementwith the observationofSvatosand coworkers14.TABLE 1- MAGNETIC MOMENTS ANDREFLECTANCE SPECTRAL DATA OF THE COMPLEXESComplex Colour(LeffAmaX(cm-1)*B.M.(C-T)MoCl3(y-pic)3JYellow3-7725641(25 73)[MoCI3(~-pic)3J(€max=3050)do3·776316[MoBr3(y-pic)3Jdo, 8974~-picls6 6667(€max=3120)pi )3JPale yellow3702(NCS)3(Y-pic)3J, 8~- i ) J53(pip)3J2220BzH)3JD p yellow4 90 45 0286*The band positionswithin parenthesesare in chloroform.631"INDIAN J. CHEM., VOL. 15A, JULY 1977Thei '1C-Nand '1C-5of the complexesoccurin th~apprOPriaterangearound2070and 815 cm-1respecively for N-bondedthiocyanate15. In thecase f [Mo(NCS) (Y-pic)aJ [Mo(NCS)a(pip)aJ,thea -C-S o<x:ursat 472and474cm-1respectivelyWhiC~further supportsMo-NCS bonding16. The'1Mo- vibrationsin thesecomplexesare recordedat 28 and 282cm-1respectively.ACkn~wledgementWe~hankDr N. K. Jha, lIT, Delhi,andDr H. C.Jha, ~onnUniversity,West Germany,for the IRspectr~.Ref etiences1. MUf'RAY, R. & SMITH,D. C., Coord.chem.Rev.,3 (1968),4 9.2. MA SEY, y, BRUMBY, P. E. & KOMAI, H., I biol.C em.. 244 (1969),1682.3. DE~ISOV,N. T., SHUVALOV,V. F., SHUVALOV,N. I.,S¥UVALOV,A. K. & SHILOV,A. E., Nature,231 (1971),4~0.4. JO~ASSEN,H. B. & BAILIN, L. J., lnorg.Synth.,7 (1963),ItO.6325. (a) SMITH, P. W. & WEDD, A. G., J. chem.Soc., (A)(1966),231; (b) SMITH, P. W. & WEDD, A. G., Ichem.Soc., (A) (1968),1377.6. ALLEN, E. A., BRISDON,B. J. & FOWLES, G. W. A.,I chem.Soc., (A) (1964),4531.7. GHOSH,S. P. & PRASAD,K. M., I less-commonMetals,36 (1974),223.8. IRVING,R. J. & STEELE,M. C., Aust.I Chem.,10 (1957),490.9. WARDLAW, W. & HARDING, A. J. I., I chem.Soc.,(1926),1592.10. PALMER, W. G., Experimentalinorganicchemistry(Cam-bridge University Press, London), 1962,415.11. FIGGIS,B. N. & LEWIS, J., Moderncoordinationchemistryeditedby J. Lewis & R. G. Wilkins (Interscience,NewYork), 1967,403.12. COTTON,F. A. & WILKINSON, G., Advanced inorganicchemistry(Interscience,New York), 1966,953.13. GRADDON,D. P. & WATTON,E. C., Aust. I Chem.,18(1965),507.14. SVATOS,G. F., SWEENY,D. M., MIZUSHIMA,S., CURRAN,C. & QUAGLIANO.J. Y., I Am. chem.Soc., 79 (1957),3313.15. KNOX, T. R. & ERIes, K., lnorg. Chem., 7 (1968),84.16. SABATINI, A. & BERTINI. I., Inorg. Chem., 4 (1965)959.

Molybdenum(III) Complexes with Unidentate Nitrogen Donors

http://nopr.niscair.res.in/bitstream/123456789/53162/1/IJCA%2015A%287%29%20630-632.pdf

Molybdenum(III) Complexes with Unidentate Nitrogen Donors

Abstract

Similar works

Full text

Available Versions

NOPR