1048-07-3Relevant academic research and scientific papers
Mechanistic studies of palladium(II)-catalyzed hydrosilation and dehydrogenative silation reactions
LaPointe, Anne M.,Rix, Francis C.,Brookhart, Maurice
, p. 906 - 917 (2007/10/03)
The cationic Pd(II) complexes, [(phen)Pd(CH3)(L)]+[BAr'4]- phen = 1,10-phenanthroline; L = Et2O, Me3SiC≡CSiMe3; Ar' = 3,5-(CF3)2C6H3) catalyze the hydrosilation and dehydrogenative silation of olefins. Hydrosilation of ethylene, tert-butylethylene, 1-hexene, and cyclohexene by HSiR3 (R = CH2CH3, C6H5) occurs in the presence of 1 mol% [(phen)Pd(CH3)(L)]+[BAr'4]-. The reaction of tert-butylethylene with HSi(i-Pr)3 in the presence of [(phen)Pd(CH3)(L)]+[BAr'4]- yields neohexane and t-BuCH=CHSi(i-Pr)3. Low-temperature NMR experiments revealed that the catalyst resting state for the silations of ethylene and alkyl-substituted olefins is [(phen)Pd(SiR3)(η2-H2C=CHR')]+[BAr'4]-. Evidence for rapid, reversible silyl migration at -70°C was observed by 1H NMR spectroscopy. Deuterium labeling studies show that the intermediate Pd(II) alkyl complexes can isomerize via a series of β-hydride eliminations followed by reinsertions of olefin prior to reaction with DSiEt3. Styrene undergoes both hydrosilation and dehydrogenative silation in the presence of [(phen)Pd(CH3)(L)]+[BAr'4]- or [(phen)Pd(η3-CH(CH3)C6H5)]+[BAr'4]- yielding ethylbenzene, R3SiCH2CH2C6H5 and trans-R3SiCH=CHPh (R = CH2CH3, CH(CH3)2). 1H NMR spectroscopy revealed that the π-benzyl complexes [(phen)Pd(η3-CH(CH2SiR3)C6H5)]+[BAr'4]- and [(phen)Pd(η3-CH(CH3)C6H5)]+[BAr'4]- are the catalyst resting states for the silation reactions of styrene.
