PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Chem 1140; Introduction to Organometallic Chemistry• General Mechanistic Principles• Reactions with Wilkinson’s CatalystA. Organometallic MechanismsOxidation State: The oxidation state of a metal is defined as the charge left on the metal after all ligands have been removed in their natural, closed-shell configuration. This is a formalism and not a physical property!d-Electron Configuration: position in the periodic table minus oxidation state.18-Electron Rule: In mononuclear, diamagnetic complexes, the total number of electrons never exceeds 18 (noble gas configuration). The total number of electrons is equal to the sum of d-electrons plus those contributed by the ligands. 18 electrons = coordinatively saturated< 18 electrons = coordinatively unsaturated.P dC lP dC lfor each Pd: Ox. state, C lP d ( I I )d: 10 (4d10 5s0) - 2 = 8electron count:bridging by lonepairs on Cl;each Cl acts as a2-electron, mononegative ligands to one of the Pd's, and a 2-electron neutral donor ligandlike PPh3 to the other: 4e- C l: 2e-C l: 2e-8e- + d8 = 16e-unsaturatedZ rC lHOx. State: 2 Cp-, 1 H-, 1 Cl- → Zr(IV)d: 4 (4d25s2) - 4 = 0electron count: 2 Cp-: 12 H- : 2 Cl- : 2 Zr : 0 16 e-, unsaturatedBonding considerationsdonation:Mvacantdsp hybridorπσbackdonation:Mfilled d orbital π∗for M-CO:M OCdspn acceptorσ− donorStructure• saturated (18 e-) complexes: - tetracoordinate: Ni(CO)4, Pd(PPh3)4 are tetrahedral- pentacoordinate: Fe(CO)5 is trigonal bipyramidal- hexacoordinate: Cr(CO)6 is octahedral• unsaturated complexes have high dx2-y2;16e- prefers square planar xyzBasic reaction mechanisms- ligand substitution: M-L + L’  M-L’ + Lcan be associative, dissociative, or radical chain.trans-effect: kinetic effect of a ligand on the role of substitution at the position trans to itself in a square or octahedral complex (ground-state weakening of bond).L  M, repels negative charge to trans position. M XL- --+++ LtP tLcXLc+ Nu-LtP tLcXLcN uLtP tXN uLcLcLtP tLcN uLcXLtP tLcN uLc+ X-- oxidative addition:[Ph3P]4Pd [Ph3P]3Pd [Ph3P]2Pd-L -LPhBrstrong σ-donor16 e-14 e-PhHHBrL2Pdagostic (2e-/3-centerbond) interactionsPhL2PdBr(+II)16 e-16 e-- reductive elimination: the major way in which transition metals are used to make C,C- and C,H-bonds!P h3PP dM e P P h3P hP h3PP dP h3PM eP hP dP h3P M eP h-Lcis!14e-?P h3P - P d12e-P h+L- migratory insertion:RZ rC pC pC l16e-C ORZ rC pC pC l18e-COZ rC pC pC l16e-RO- -elimination/hydrometalation:RZ rC pC pC lRZ rC pC pC lRZ rC pC pC lHHHβ -eliminationhydrometalation- olefin metathesis:( O C )5C rO M eP h18e-Fischer carbene complexO E tΔ , 80 °CP hO M e+( O C )5C rO E t( O C )5C rO M eP hE t O- transmetalation:R-M + M’-X  R-M’ + M-XSummary of Mechanisms:- ligand substitution- oxidative addition/reductive elimination- migratory insertion/-elimination (carbo-, hydrometalation)- alkene metathesis- transmetalationReactions with Wilkinson’s CatalystAlkene HydrogenationCO2MeH2cat. RhCl(PPh3)3H2cat. PtO2CO2MeCO2Me96:449:26PPh3Rh HPPh3ClHPPh3Rh HPPh3ClHRRHHcoordinationRmigratoryinsertionreductiveeliminationoxidativeaddition-PPh3+PPh3[RhCl(PPh3)2]RhCl(PPh3)3H HPPh3Rh HPPh3HClRMechanismOi-PrOH, KOHcat. RhCl(PPh3)3OHi-PrOH, KOHcat. RhCl(PPh3)3OHReductionsWhere does the hydrogen come from????EtorEtHSiMe2Phcat. RhCl(PPh3)3SiMe2PhEtHydrosilylationTHPOOTHPCHO0.4 equivRhCl(PPh3)3CH2Cl240 oC, 20 hOTHPOHHOTHPHydrocarbonylationPhOEt1.0 equiv RhCl(PPh3)3Ph HEt93% retentionDecarbonylationNHOH2, COcat. RhCl(PPh3)3NHOCHOother minor productsHydroformylationPh1. catecholborane cat. RhCl(PPh3)3 2. H2O2, OH-OHPhprimary alcoholif the catalyst ispartially oxidizedMarkownikow HydroborationTBDMSOcat.