Carbon-Hydrogen Bond Stannylation and Alkylation Catalyzed by Nitrogen-Donor-Supported Nickel Complexes: Intermediates with Ni-Sn Bonds and Catalytic Carbostannylation of Ethylene with Organostannanes

The reaction of H2C=CHSnR3 with C6F5H, where R = Bu, Bn, Ph, was catalyzed by Ni(COD)(2) and the nitrogen donor ancillary ligand (MeNC5H4NPr)-Pr-i. These reactions produced the stannylation products C6F5SnR3 (1(R)) and C-H alkylation products C6F5CH2CH2SnR3 (3(R)). The Bu substituent provided the best selectivity for stannylation, whereas the Ph substituent provided primarily the alkylation product. The catalytic intermediate ((MeNC5H4NPr)-Pr-i)Ni(eta(2)-H2C=CHSnR3)(2) (2(R)) was observed by NMR spectroscopy and isolated in the case of R = Ph. A second catalytic intermediate, cis-((MeNC5H4NPr)-Pr-i)(2)Ni(C6F5)(SnR3) (4(R)), was observed by NMR spectroscopy and isolated for R = Bn, Ph by the reaction of C6F5SnR3 with (MeNC5H4NPr)-Pr-i and Ni(COD)(2). The reaction of C6F5SnR3 with ethylene in the presence of catalytic (MeNC5H4NPr)-Pr-i and Ni(COD)(2) provided the carbostannylation product 3(R). Mechanistic studies of the C-H stannylation/alkylation mechanism were performed to propose a mechanistic manifold for these transformations.