Phenyl nickel complexes with a chelating P,N ligand. Structures of Ph(3)P=CHC(NPh)Ph and [NiPh{Ph(2)PCH-C(-NPh)Ph}{Ph(3)P=CHC(=NPh)Ph-N}]

The complexes [NiPh{Ph(2)PCH(sic)C((sic)NPh)Ph}{Ph(3)P=CHC(=NPh)Ph-N}] and [NiPh{Ph(2)PCH(sic)C((sic)NPh)Ph}(PR(3))] (PR(3) = PMe(3), PMe(2)Ph or PMePh(2)) were prepared starting from [Ni(cod)(2)] (cod = cycloocta-1,5-diene) and the phosphorus ylide Ph(3)P=CHC(=NPh)Ph I in the presence of a tertiary phosphine. Surprisingly, only the first complex was isolated when PPh(3) and P(C6H11)(3) were used, whereas the other phosphines led to the corresponding PR(3) complexes together with variable amounts of the first depending on their steric demand. The known synthesis of I has been optimized to yields close to 90%. Experiments carried out to study the potential of the nickel compounds as catalysts for ethylene oligomerization showed the stoichiometric formation of styrene and minor amounts of low-molecular-weight linear alpha-olefins. The molecular structures of I and the first complex have been determined by X-ray diffraction. In the nickel complex the co-ordination around the metal is distorted square planar, with P(1)-Ni-C(1) and N(1)-Ni-N(2) angles of 90.30(8) and 97.18(8)degrees, respectively.