M C. White. Chem 153 Structure bonding-g. Week of September 17, 2002 Electron Counting Rh PhP PPh PhaP M Pall Wilkinson's catalyst e (Pha P)3RhCI metal: d 8 8e metal: d s Brookhart polymerization analyst precursor complex: 16e- Brookhart JACS 1995(117)6414 P F lex: 18 e- Ar Php Noyori hydrogenation Palladium"tetrakis"triphenylphosphine pling catalyst H Rull ofF gan Olefin dihydroxylation ligands 126 talyst Noyori JACS 1998(120)13529 complex: 18 e- Que JACS2001(123)672 com plex: 18 e-
Electron Counting M.C. White, Chem 153 Structure & Bonding -9- Week of September 17, 2002 Ph3P Rh Cl PPh3 PPh3 Ph3P RhI Cl PPh3 PPh3 P Ru P H2 N N H2 Cl Cl Ar2 Ar2 O O P RuII P N N Cl Cl O O Ar2 Ar2 H2 H2 N N Pd Me Me N N PdII Me Me N Fe N N OTf N OTf N Fe N II N OTf N OTf PPh3 PPh3 Pd Ph3P Ph3P PPh3 PPh3 Pd0 Ph3P Ph3P Wilkinson's catalyst (Ph3P)3RhCl ligands: 8emetal: d8, 8ecomplex: 16 eligands: 12emetal: d6, 6ecomplex: 18 e- Noyori hydrogenation catalyst Brookhart polymerization catalyst precursor ligands: 8e- metal: d8, 8e- complex: 16 e- Olefin dihydroxylation catalyst ligands: 12e- metal: d6, 6e- complex: 18 e- ligands: 8e- metal: d10, 10e- complex: 18 e- Palladium "tetrakis" triphenylphosphine cross coupling catalyst Noyori JACS 1998 (120) 13529. Que JACS 2001 (123) 6722. Brookhart JACS 1995 (117) 6414
M C. White. Chem 153 Structure bonding-10- Week of September 17, 2002 Unsaturated ligands orr of e- m -coordination charge donated m-coordination charge donated m2-alkene R 2 m-alkynyl n2-alkyne H m-Cp(cyclopentadienyl) m-Cp(cyclopentadienyl) m3-allyl m-acetate acetate
M M R M H M O O M η1-coordination Formal charge # of e- donated -1 -1 -1 -1 -1 -1 2 2 2 2 2 2 η1-aryl η1-alkenyl η1-alkynyl η1-Cp (cyclopentadienyl) η1-acetate M η1-allyl M M R H M M O O M 0 0 0 -1 -1 -1 6 2 2 6 4 4 η6-arene η2-alkene η2-alkyne η5-Cp (cyclopentadienyl) η2-acetate ηx-coordination Formal charge # of edonated M η3-allyl = M M Unsaturated Ligands M.C. White, Chem 153 Structure & Bonding -10- Week of September 17, 2002
M C. White. Chem 153 Structure bonding-1l Week of September 17, 2002 Electron Counting /I (Cy)3 P(y)3 H H R H:⊙ Me,F Me, P P(Cy)3 P(Cy)3 Crabtree's dehydrogenation B catalyst direct observation metal: d. 6e- fC-H->C-M metal: d. 6e Crabtree JACS 1987(109)8025 Bergman OM1984(3)508 complex: 18e ⊙ Ru Rull CH Ru-Ru bond =2 e- note: metal oxidation Ru I ligands:12e- ligands: 12 e- Brintzinger catalyst Hidai catalyst for metal: d5, Se- metal:d,5e metal: d0 0e propargylic substition Ru l: le- Brintzinger JOMC 1985(228)63. L complex: 16e- complex: 18 e- complex: 18 e- Hidai JACS 2002(124)7900
Electron Counting II M.C. White, Chem 153 Structure & Bonding -11- Week of September 17, 2002 H Ir H O O P(Cy)3 P(Cy)3 CF3 H IrIII H O O P(Cy)3 P(Cy)3 CF3 ligands: 12emetal: d6, 6ecomplex: 18 eCrabtree's dehydrogenation catalyst Rh H Me H 3P Cp* RhIII H Me3P H ligands: 12emetal: d6, 6ecomplex: 18 eBergman: direct observation of C-H-> C-M Zr Cl Cl Brintzinger catalyst ZrIV Cl Cl ligands: 16emetal: d0, 0ecomplex: 16 eRu S Ru S CH3 CH3 Cl Cl RuIII S RuIII S CH3 CH3 Cl Cl Ru-Ru bond = 2 enote: metal oxidation state doesn't change Hidai catalyst for propargylic substition ligands: 12 emetal: d5, 5eRu 2: 1 ecomplex: 18 eRu 1 ligands: 12 e- metal: d5, 5e- Ru 1: 1 e- complex: 18 e- Ru 2 Brintzinger JOMC 1985 (228) 63. Hidai JACS 2002 (124) 7900 Crabtree JACS 1987 (109) 8025. BergmanOM 1984 (3) 508
M C. White. Chem 153 Structure bonding-12 Week of September 17, 2002 Weakly Coordinating Counterions Common weakly coordinating counterions used in organotransition metal catalysis to generate cationic catalysts Weakly coordinating anions generally have: 1. low charge. 2. high degree of TfO-<CIO4 <BF4<PF6<SbF6 BAr'4([3, 5-C6H3(CF3)214) harge delocalization ( individual atom has a high More weakly coordinating concentration of charge), 3. steric bulk Synthesis Metathesis: Ag() halide abstraction. Most general approach for the introduction of The least coordinating anion weakly coordinating counterion he exanalocarboranes (CBuH,X6 Me e equiv. Ag st NCCH3 CH:CN NCCHa(SbF6)2 Me note neutral solvent Jacobsen JACS 2001(123)7194 Protonolysis laces l' H(OEt,h BAr (BAr40 Strem: Silver hexabrom carborane \(Ag* CB, H Br6)1g=$594 t Strauss Chem. Rev. 1993(93)927 Brookhart JACS 1999(121)10634 Reed Acc. Chem. Res 1998(31)133
Weakly Coordinating Counterions The least coordinating anion: hexahalocarboranes (CB11 H6X6 - ) Strem: Silver hexabromocarborane (Ag +CB11 H6Br6 -) 1g = $594 Strauss Chem. Rev. 1993 (93) 927. Reed Acc. Chem. Res. 1998 (31) 133. Fe Cl Cl N N Me Me N N CH3CN Fe NCCH3 NCCH3 N N Me Me N N (SbF6 - )2 2 equiv. Ag +SbF6 - 2+ Jacobsen JACS 2001 (123) 7194. Common weakly coordinating counterions used in organotransition metal catalysis to generate cationic catalysts: Weakly coordinating anions generally have: 1. low charge, 2. high degree of charge delocalization (i.e. no individual atom has a high concentration of charge), 3. steric bulk. Synthesis Metathesis: Ag (I) halide abstraction. Most general approach for the introduction of weakly coordinating counterions. Protonolysis M.C. White, Chem 153 Structure & Bonding -12- Week of September 17, 2002 note: neutral solvent replaces L- in rxn. TfO-< ClO4 - < BF4 - < PF6 - < SbF6 - < BAr'4 (B[3,5-C6H3(CF3)2]4) More weakly coordinating N N Ar Ar Ni Me Me Et2O N N Ar Ar Ni Me OEt2 H +(OEt2)2 BAr'4 - + (BAr'4 - ) Brookhart JACS 1999 (121) 10634
MC.White,Chem 153 Structure bonding-13- Week of September 17, 200 Electron Counting lll does not contribute to the COD=1.5-cvclooctadie electron count for complex P(Cy)3 Ir :P(Cy3 PF6 PF H3CCN NCCH3 CHaCO ncCHa H3CaN CH3CN Crabtree's catalysts for hydrogenations ands 8e. metal:d.6e. etal: d 8 8e complex: 18 e- plex: 16 e- review: Crabtree Acct. Chem. Res 1979(12)331: Ist synthesis: Mann OM1982(1)485 catalytic enyne cycloisomerizationsfrostJACS2002(124)5025 BPh3 Rh rh o (SbF)3 Ty-NBD-norbormadier Zwitterionic complex ds:10 epoxidation catalyst used in hydroformylations tal: ds Questi complex: 18e- Fe 2 ligands. xe Ist synthesis: Schrock and Osborn/norg. Chem. 1970(9)2339 Jacobsen 2001(123)7194.metal: d, Se- metal: d, xe- hydroformylation: Alper Chem. Comm. 1993, 233 complex x e- complex:xe-
Electron Counting III M.C. White, Chem 153 Structure & Bonding -13- Week of September 17, 2002 Ir N P(Cy)3 (PF6-) IrI N P(Cy)3 PF6 BPh3 Rh+ BPh3 RhI Ru H3CCN NCCH3 H3CCN (PF6-) RuII CH3CN NCCH3 CH3CN PF6 Fe N O N Me Me N N (SbF6- Fe )3 N N N N O O Me Me + Crabtree's catalysts for hydrogenations + weakly coordinating anion does not contribute to the electron count for complex ligands: 8 emetal: d8, 8ecomplex: 16 ereview: Crabtree Acct. Chem. Res. 1979 (12) 331. COD = 1,5-cyclooctadiene NBD = norbornadiene "Zwitterionic complex" used in hydroformylations 1st synthesis: Schrock and OsbornInorg. Chem. 1970 (9) 2339. hydroformylation: Alper Chem. Comm.1993, 233. ligands: 10 emetal: d8, 8ecomplex: 18 eligands: 12 e- metal: d6, 6e- complex: 18 e- 1st synthesis: Mann OM 1982 (1) 485. catalytic enyne cycloisomerizations: Trost JACS 2002 (124) 5025. + + Jacobsen JACS 2001 (123) 7194. ligands: x emetal: dx, 5ecomplex: x eFe 1 ligands: x e- metal: dx, xe- complex: x e- Fe 2 3+ epoxidation catalyst Question: