Organometallic-Chemistry.ppt

Chem1140;IntroductiontoOrganometallicChemistry•GeneralMechanisticPrinciples•ReactionswithWilkinson’sCatalystA.OrganometallicMechanismsOxidationState:Theoxidationstateofametalisdefinedasthechargeleftonthemetalafterallligandshavebeenremovedintheirnatural,closed-shellconfiguration.Thisisaformalismandnotaphysicalproperty!d-ElectronConfiguration:positionintheperiodictableminusoxidationstate.18-ElectronRule:Inmononuclear,diamagneticcomplexes,thetotalnumberofelectronsneverexceeds18(noblegasconfiguration).Thetotalnumberofelectronsisequaltothesumofd-electronsplusthosecontributedbytheligands.18electrons=coordinativelysaturated18electrons=coordinativelyunsaturated.PdClPdClforeachPd:Ox.state,ClPd(II)d:10(4d105s0)-2=8electroncount:bridgingbylonepairsonCl;eachClactsasa2-electron,mononegativeligandstooneofthePd's,anda2-electronneutraldonorligandlikePPh3totheother:4e-Cl:2e-Cl:2e-8e-+d8=16e-unsaturatedZrClHOx.State:2Cp-,1H-,1Cl-Zr(IV)d:4(4d25s2)-4=0electroncount:2Cp-:12H-:2Cl-:2Zr:016e-,unsaturatedBondingconsiderationsdonation:Mvacantdsphybridorbackdonation:MfilleddorbitalforM-CO:MOCdspnacceptordonorStructure•saturated(18e-)complexes:-tetracoordinate:Ni(CO)4,Pd(PPh3)4aretetrahedral-pentacoordinate:Fe(CO)5istrigonalbipyramidal-hexacoordinate:Cr(CO)6isoctahedral•unsaturatedcomplexeshavehighdx2-y2;16e-preferssquareplanarxyzBasicreactionmechanisms-ligandsubstitution:M-L+L’M-L’+Lcanbeassociative,dissociative,orradicalchain.trans-effect:kineticeffectofaligandontheroleofsubstitutionatthepositiontranstoitselfinasquareoroctahedralcomplex(ground-stateweakeningofbond).LM,repelsnegativechargetotransposition.MXL---+++LtPtLcXLc+Nu-LtPtLcXLcNuLtPtXNuLcLcLtPtLcNuLcXLtPtLcNuLc+X--oxidativeaddition:[Ph3P]4Pd[Ph3P]3Pd[Ph3P]2Pd-L-LPhBrstrong-donor16e-14e-PhHHBrL2Pdagostic(2e-/3-centerbond)interactionsPhL2PdBr(+II)16e-16e--reductiveelimination:themajorwayinwhichtransitionmetalsareusedtomakeC,C-andC,H-bonds!Ph3PPdMePPh3PhPh3PPdPh3PMePhPdPh3PMePh-Lcis!14e-?Ph3P-Pd12e-Ph+L-migratoryinsertion:RZrCpCpCl16e-CORZrCpCpCl18e-COZrCpCpCl16e-RO--elimination/hydrometalation:RZrCpCpClRZrCpCpClRZrCpCpClHHH-eliminationhydrometalation-olefinmetathesis:(OC)5CrOMePh18e-FischercarbenecomplexOEt,80癈PhOMe+(OC)5CrOEt(OC)5CrOMePhEtO-transmetalation:R-M+M’-XR-M’+M-XSummaryofMechanisms:-ligandsubstitution-oxidativeaddition/reductiveelimination-migratoryinsertion/-elimination(carbo-,hydrometalation)-alkenemetathesis-transmetalationReactionswithWilkinson’sCatalystAlkeneHydrogenationCO2MeH2cat.RhCl(PPh3)3H2cat.PtO2CO2MeCO2Me96:449:26PPh3RhHPPh3ClHPPh3RhHPPh3ClHRRHHcoordinationRmigratoryinsertionreductiveeliminationoxidativeaddition-PPh3+PPh3[RhCl(PPh3)2]RhCl(PPh3)3HHPPh3RhHPPh3HClRMechanismOi-PrOH,KOHcat.RhCl(PPh3)3OHi-PrOH,KOHcat.RhCl(PPh3)3OHReductionsWheredoesthehydrogencomefrom????EtorEtHSiMe2Phcat.RhCl(PPh3)3SiMe2PhEtHydrosilylationTHPOOTHPCHO0.4equivRhCl(PPh3)3CH2Cl240oC,20hOTHPOHHOTHPHydrocarbonylationPhOEt1.0equivRhCl(PPh3)3PhHEt93%retentionDecarbonylationNHOH2,COcat.RhCl(PPh3)3NHOCHOotherminorproductsHydroformylationPh1.catecholboranecat.RhCl(PPh3)32.H2O2,OH-OHPhprimaryalcoholifthecatalystispartiallyoxidizedMarkownikowHydroborationTBDMSOcat.RhCl(PPh3)3TBDMSOHHCycloisomerization