Exploring the Utility of Neutral Rhodium and Iridium 2-P,O and 2-P(S),O Complexes as Catalysts for Alkene Hydrogenation and Hydrosilylation
文摘
Heating of [(COD)M(2-3-PiPr2-2-NMe2-indene)]+X- (M = Rh or Ir; X = BF4, PF6; COD = 4-1,5-cyclooctadiene) in a mixture of water and THF (48 h, 60 C) afforded the neutral (COD)M(2-P,O)complexes (M = Rh, 5a, 80%; M = Ir, 5b, 74%). Similarly, thermolysis of [(COD)M(2-3-P(S)iPr2-2-NMe2-indene)]+BF4- (M = Rh or Ir) in a mixture of water and CH2Cl2 (14 h, 60 C) produced theneutral (COD)M(2-P(S),O) complexes (M = Rh, 13a, 91%; M = Ir, 13b, 90%). Subsequent preparationof 1-PiPr2-2-indanone (8, 91%) enabled the non-hydrolytic synthesis of 5b in 70% isolated yield viatreatment with 0.5[(COD)IrCl]2 in the presence of NEt3. Lithiation of (o-PiPr2)phenol followed byquenching with 0.5[(COD)IrCl]2 afforded the neutral (COD)Ir(2-P,O) complex 10 (91%). Single-crystalX-ray diffraction data are provided for 5b, 10, 13a, and 13b. Whereas 5a, 13a, and 13b performedpoorly as catalysts for the hydrogenation of alkenes, the known complex (COD)Ir(OPh)(PCy3) 2 as wellas 5b and 10 proved to be excellent catalysts for hydrogenation of mono-, di-, and trisubstituted alkenesubstrates under mild conditions (22 C, ~1 atm H2). Complexes 13a,b were also shown to be competentcatalysts for addition of triethylsilane to styrene.