Reactivity of the diphosphinodithio ligated nickel(0) complex toward alkyl halides and resultant nickel(i) and nickel(ii)–alkyl complexes

Abstract

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)₂CHI 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)₂CHI 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.