Organometallics 2010, 29, 2916–2925电化学(3)

2918Organometallics,Vol.29,No.13,2010

Scheme1.SyntheticPathwaysfortheBismetallabenzenes5a-dBridgedbyDiisocyanide

Ligands

Huangetal.

isocyanide-coordinatedruthenabenzene2(eq1).9Giventheimportantroleofdiisocyanidesinmolecularelectronicsandrecentprogressinoptoelectronicmaterialsmentionedabove,wearemotivatedtodesignanewbismetallabenzenesystemwithdiisocyanideasthebridgingligands.Ofparticularinter-estisthediisocyanide-bridgedbismetallabenzenesconstitut-inglargeconjugatedsystem,whichmightexhibitspecialelectrochemicalandotherphysicochemical

properties.

Inthiswork,wehavesuccessfullyconstructedaseriesofbisosmabenzenesusingdiisocyanideswithdifferentlinkingspacersasthebridgingligands.Asacomparativestudy,abisosmafuranbridgedby1,4-phenylenediidocyanidehasalsobeensynthesized.Theelectrochemicalpropertiesofseveralcomplexeshavebeenstudiedbycyclicvoltammetry.

ResultsandDiscussion

SynthesisandCharacterizationofDiisocyanide-BridgedBisosmabenzenesfromLigandSubtitutionReactions.Asal-readystated,inourstudiesonthereactivityofruthenaben-zeneswiththeisocyanides,9wehavefoundthatoneoftheClligandsin1canbereadilyreplacedbytBuNCtoproducestableisocyanide-coordinatedruthenabenzene2(eq1).Weenvisionedthatanalogousosmambenzenecomplex[Os-(CHC(PPh3)CHC(PPh3)CH)Cl2(PPh3)2]OH(3)21mayalsoundergosimilarligandsubstitutionreactionwithdiisocya-nide.Thus,wehavecarriedoutthereactionof3withaseriesofdiisocyanideligands,withthehopetoobtainbismetalla-benzenecomplexes.Asexpected,anumberofbisosmaben-zeneshavebeensuccessfullysynthesizedandfullycharac-terized.ThegeneralsyntheticrouteforthepreparationofbismetallabenzenesisoutlinedinScheme1.

Treatmentofosmabenzene[Os(CHC(PPh3)CHC(PPh3)-CH)Cl2(PPh3)2]OH(3)with0.5equivofdiisocyanideligandCN-Ln-NC(4a-d,Lnisthelinkingspacer)inthepresenceofNH4PF6atroomtemperaturefor0.5-1.0hledtotheformationofbisosmabenzenes5a-d,whichwereisolatedasgreenishsolidsinyieldsrangingfrom58%to78%.Itwasfoundthatthereactionproceededveryslowlyintheabsence

(21)Xia,H.;He,G.;Zhang,H.;Wen,T.B.;Sung,H.H.Y.;Williams,I.D.;Jia,G.J.Am.Chem.Soc.2004,126,6862.

ofNH4PF6,whileadditionofNH4PF6couldspeedupthereaction.ProbablyNH4PF6wasaddedtoabstractonechlor-ideligandfirst,sothattheligandsubstitutionreactioncanbeaccelerated.Inthesolidstateandunderaninertatmosphere,thesecomplexesareallstableatroomtemperatureforatleastonemonthandcanbestoredat0οCforatleastseveralmonthswithoutappreciabledecomposition.However,itisimportanttonotethatcomplexes5a-dcanslowlydecomposeinsolutionatambienttemperature,resultingintheformationofamixtureofunidentifiedproducts.

Allofthecompoundshavebeencharacterizedbyelemen-talanalysis,IR,and1H,13C{1H},and31P{1H}NMRspec-trometry.Althoughthemolecularstructuresof5a-dhavenotbeencharacterizedsofarbyX-raydiffraction,duetothelackofX-rayqualitysinglecrystals,itisbelievedthateachmoleculehastwosymmetricallyrelatedunits,asinferredfromtheNMRdata.SelectedNMRandIRdataforthebisosmabenzenes5a-daregiveninTable1.Onthewhole,theNMRdataof5a-daresimilartoeachotherwithrespecttochemicalshiftsandsignalpatterns.Inthe31P{1H}NMRspectrum,eachoftheosmiumcomplexes5a-dshowsonesingletintheregionδ=-1.20to-1.83attributedtoOsPPh3andanothertwosingletsforCPPh3intheregionsδ=19.74-20.65and24.88-25.58ppm,respectively.Inthe1

HNMRspectrumthecharacteristicsignalsforOsCHofthemetallacycleareobservedatδ=14.54-15.74ppmwithaH-Pcouplingconstantofapproximately25Hzandδ=16.36-17.45ppmwithaH-Pcouplingconstantofapproxi-mately19Hz.TheprotonresonancesonthecarbonsparatotheOscentersappearatδ=7.95-9.09ppmaccordingto1

H-13CHSQC.Incomparisonto3,the1HNMRsignalsoftheringprotonsfor5a-dareshiftedconsiderablyupfielded.5n,21Asimilartrendwasobservedforthemeta-carbonsinthe13CNMRspectrum,inwhichthesignalsofγ-CHareobservedintherangeδ=152.76-158.91ppm,whereasthesignalsofortho-andpara-carbonstotheOscentersareshifteddownfield,whichappearintherangesδ=238.03-259.75and114.32-120.41ppm.Additionally,theisocyano-carbonsignalsaregenerallyoflowintensity,22whichappearasasingletatδ=143.15-145.15ppm.Inparticular,onlyoneν(CtN)absorptionisobservedforeachcomplexat2081-2109cm-1intheFTIRspectra,indicatingthepresenceofonetypeofisocyanogroupineachcomplex.

(22)Efraty,A.;Feinstein,I.;Wackerle,L.;Goldman,.Chem.1980,45,4059.