Silicon-Mediated Coupling of Carbon Monoxide, Ammonia, and Primary Amines to Form Acetamides.

For the first time, a direct transformation of CO, NH3 , and primary amines into acetamides, mediated by a main-group element (silicon), is reported. Starting point is the selective deoxygenative reductive homocoupling of two CO molecules by the Fc-bis(silylene) 1 a (Fc=ferrocendiyl) as a reducing agent, which forms the ferrocendiyl-bridged disila(μ-O)(μ-CCO)ketene intermediate 2 a. Exposing 2 a to NH3 (1 bar, 298 K) and benzylamine yields the Fc-disiloxanediamines [Fc(RHNSi-O-SiNHR)] 5 a (R=H) and 5 b (R=benzyl) under release of the respective acetamides H3 CC(O)NHR, as confirmed by 13 C-isotope-labelling experiments. IR and NMR studies of the reaction reveal a four-step mechanism involving an N-silylated carboxamide that can be isolated and fully characterized. The striking reaction mechanism for this unprecedented transformation involves a facile Si-C bond cleavage and ammonolysis of a Si-O bond, and has been demonstrated experimentally and by quantum-chemical calculations.