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.