Carbon−Carbon Bond Activation of R−CN (R = Me, Ar, iPr, tBu) Using a Cationic Rh(III) Complex

Addition of 1.0 equiv of Ph3SiH to Cp*(PMe3)Rh(Me)(CH2Cl2)+BAr'4- (1) resulted in release of methane and quantitative formation of Cp*(PMe3)Rh(SiPh3)(CH2Cl2)+BAr'4- (2). Subsequent addition of 1.0 equiv of MeCN to 2 caused immediate displacement of dichloromethane to form the eta1-nitrile adduct Cp*(PMe3)Rh(SiPh3)(NCMe)+BAr'4- (3). Upon standing at room-temperature overnight, complex 3 converted quantitatively to another product which has been characterized as the C-C activation product, Cp*(PMe3)Rh(Me)(CNSiPh3)+BAr'4- (5). Addition of other nitrile substrates (R-CN, R = Ph, (4-CF3)Ph, (4-MeO)Ph, iPr, tBu) to 2 also resulted in C-C activation of the R-CN bond to form Cp*(PMe3)Rh(R)(CNSiPh3)+BAr'4-. Evidence for an eta2-iminoacyl intermediate complex, Cp*(PMe3)Rh(eta2-C(R)=N(SiPh3)+BAr'4-, is also presented.