Mechanistic Studies of Si−CN and C−NC Bond Activation of Silylnitriles and Alkyl Isonitriles by Rhodium Porphyrin Radical: Novel Cyanide Transfer
摘要:
The Si-CN and C-NC bonds of silylnitriles and alkyl isonitriles were activated by (tetramesitylporphyrinato) rhodium(II), Rh(tmp), to give rhodium porphyrin silyls or alkyls and rhodium porphyrin cyanide, respectively. Pyridine and triphenylphosphine promoted the rates and yields of the reactions with silylnitriles, but inhibited the rates and yields of the reactions with isonitriles. The reaction of Rh( tmp) with Me3SiCN exhibited second-order kinetics (rate = k(obs)[Rh(tmp)][Me3SiCN]) at a sufficiently high concentration of pyridine. The reaction with BuNC showed fourth-order kinetics, second-order in each of the reactants; rate = k(obs)[Rh(tmp)](2)[BuNC](2). A novel cyanide transfer rate-determining step was proposed to account for the reaction mechanism.
Oxidative Addition of Silyl Cyanides to Rhodium Porphyrin Radical: Isocyanide or Cyanide Transfer Mechanism
作者:Kin Shing Chan、Lirong Zhang、Chun Wah Fung
DOI:10.1021/om049253h
日期:2004.12.1
Rhodium porphyrin radical, coordinated with pyridine, activated the carbon−silicon bond of silyl cyanides to yield rhodium porphyrin silyls and cyanide. The reaction with Me3SiCN exhibited second-order kinetics, rate = kobsd[Rh(tmp)][Me3SiCN], at a sufficiently high concentration of pyridine, and the mechanism was interpreted to involve a cyanide or isocyanide group transfer to rhodium radical.
铑卟啉自由基与吡啶配合,激活了甲硅烷基氰化物的碳-硅键,从而生成了铑卟啉甲硅烷基和氰化物。与Me 3 SiCN的反应在吡啶浓度足够高的情况下显示出二级动力学,速率= k obsd [Rh(tmp)] [Me 3 SiCN],并且该机理被解释为涉及氰化物或异氰基转移至铑自由基。