The homogeneously catalysed addition reaction of polyhalogenoalkanes to olefins by divalent arylnickel complexes: comparative reactivity and some important mechanistic leads

Abstract

In comparative studies some bis(ortho-chelated) arylnickel compounds of the type [Ni{C{6}H{3}(CH{2}NRR'){2}-2, 6}X] have been tested for activity in the Kharasch addition reaction of polyhalogenoalkanes to an alkene double bond using methyl methacrylate as substrate and carbon tetrachloride as reagent. The N-donor substituent combination R = R' = Me produces a complex with higher reactivity than either of the combination Et,Et, and Me,i-Pr, and the influence of the halide X is small; catalytic efficacy decreases in the order I ~ Br > Cl (R = R' = Me). The related palladium and platinum complexes [M{C{6}H{3}(CH{2}NMe{2}){2}-2,6}X] (M = Pt, X = I; M = Pd, X = Br) show no catalytic activity in this reaction, though the complex [Pd{C{6}H{3}(CH{2}NMePh){2}-2,6}Br] does initiate alkene polymerization. A mechanism consistent with these results is outlined.