Reactivity of cyanogen with monocarbonylnickel(0) complexes. Examples of combined oxidative substitution and internal ligand substitution

The complex [Ni(CO)(dppb)2] (dppb = Ph2P[CH2]4PPh2) undergoes a two-stage reaction with C2N2 in CH2Cl2, at room temperature. The first stage gives almost equivalent quantities of [{Ni(CN)2(dppb)}2] and [Ni(CO)2(dppb)], whereas quantitative conversion of [Ni(CO)2(dppb)] into [{Ni(CN)2(dppb)}2] and CO is obtained in the second stage. The complexes [Ni(CO)(dppb){P(OR)3}](R = Et or Ph) react in a similar way under particular conditions. A kinetic investigation has been carried out on the first system and a reaction mechanism is proposed for its first stage.