Experimental and theoretical study on activation of the C–H bond in pyridine by [Mm]− (M = Cu, Ag, Au, m = 1–3)

Abstract

Activation of the C–H bond of pyridine by [M_m]⁻ (M = Cu, Ag, Au, m = 1–3) is investigated by experiment and theory. Complexes of coinage metal clusters and the pyridyl group, [M_m–C₅H₄N]⁻, are produced from reactions between metal clusters formed by laser ablation of coinage metal samples and pyridine molecules seeded in argon carrier gas. We examine the structure and formation mechanism of these pyridyl–coinage metal complexes. Our study shows that C₅H₄N bonds to the metal clusters through a M–C σ bond and [M_m–C₅H₄N]⁻ is produced via a stepwise mechanism. The first step is a direct insertion reaction between [M_m]⁻ and C₅H₅N with activation of the C–H bond to yield the intermediate [HM_m–C₅H₄N]⁻. The second step is H atom abstraction by a neutral metal atom to yield [M_m–C₅H₄N]⁻.