C-N coupling in the gas-phase reactions of ammonia and [M(CH)]+ (M = Ni, Pd, Pt): a combined experimental/computational exercise.

Electrospray ionization (ESI) of methanolic solutions of monomeric nickel(II) acetate, [Ni(CH(3)COO)(2)], and tetrameric platinum(II) acetate, [Pt(4)(CH(3)COO)(8)], leads to the formation of the corresponding methylidyne complexes [M(CH)](+) (M = Ni, Pt), which react with ammonia under C-N coupling. While the product couples M/[CH(4)N](+) and [M(CH(2)N)](+)/H(2) are observed for both metals, hydrogen-atom expulsion to generate [M(CHNH(2))](+)/H is only observed in the case of the nickel-containing system, and the proton transfer leading to M/[NH(4)](+) is limited to platinum. Attempts to conduct related experiments with [Pd(CH)](+)/NH(3) failed. The mechanisms that explain the experimentally observed reaction channels have been investigated computationally using the B3LYP functional for all metals of the nickel group (M = Ni, Pd, Pt). In line with labeling experiments using the reaction pairs [M(CD)](+)/NH(3) and [M(CH)](+)/ND(3) (M = Ni, Pt), two different mechanistic scenarios of the dehydrogenation process are operative for the Ni and Pt systems, respectively.