DFT computational study of the mechanism of allyl halides carbonylation catalyzed by nickel tetracarbonyl

A theoretical investigation at the DFT(B3LYP) level on the carbonylation reaction of allyl bromide catalyzed by nickel tetra-carbonyl Ni(CO)₄ is discussed. The computational results show the following: (i) Three main steps characterize the catalytic cycle: (a) an oxidative addition step, (b) a carbonylation step, and (c) a reductive elimination step where the acyl product is obtained and the catalyst is regenerated. (ii) Both Ni(CO)₃ and Ni(CO)₄ complexes can behave as "active" catalytic species. (iii) The oxidative addition leads to the formation of either η ³ or η¹-allyl nickel complexes, which are involved in a fast equilibrium. (iv) The carbonylation occurs much more easily on the η¹ than on the η³ intermediates.