Reactivity of the diphosphinodithio ligated nickel(0) complex toward alkyl halides and resultant nickel( I) and nickel( II)- alkyl complexes

Diphosphinodithio ligated complexes of nickel(0), nickel(i) and nickel(ii)-alkyl with a reactivity relevant to the C-C bond formation were described. Stoichiometric reactions of the nickel(0) complex, [(P2S2)Ni] ([1](0), P2S2 = (Ph2PC6H4CH2S)(2)(C2H4)), with alkyl halides (RX) such as C6H5CH2Br, C2H3CH2Br, C2H5I and (CH3)(2)CHI were investigated, from which the products were found to be highly dependent on the nature of RX used. Oxidative addition of C2H3CH2Br to [1](0) provides the stable Ni(ii)-alkyl complexes [1-allyl](+). The reaction of [1](0) with C6H5CH2Br proceeds through a radical pathway resulting in the formation of the nickel(i) complex [1](+) and an organic homo-coupled product 1,2-diphenylethane. Oxidative addition of C2H5I or (CH3)(2)CHI to [1](0) can be achieved but it competes with the halogen atom abstraction reaction as found for C6H5CH2Br. [1](0) was shown to be an active catalyst for the coupling reactions of primary halides and alkyl Grignard reagents.