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 MeNC5H4NiPr. These reactions produced the stannylation products C6F5SnR3 (1R) and C–H alkylation products C6F5CH2CH2SnR3 (3R). The Bu substituent provided the best selectivity for stannylation, whereas the Ph substituent provided primarily the alkylation product. The catalytic intermediate (MeNC5H4NiPr)­Ni­(η2-H2CCHSnR3)2 (2R) was observed by NMR spectroscopy and isolated in the case of R = Ph. A second catalytic intermediate, cis-(MeNC5H4NiPr)2Ni­(C6F5)­(SnR3) (4R), was observed by NMR spectroscopy and isolated for R = Bn, Ph by the reaction of C6F5SnR3 with MeNC5H4NiPr and Ni­(COD)2. The reaction of C6F5SnR3 with ethylene in the presence of catalytic MeNC5H4NiPr and Ni­(COD)2 provided the carbostannylation product 3R. Mechanistic studies of the C–H stannylation/alkylation mechanism were performed to propose a mechanistic manifold for these transformations.