Phenyl nickel complexes with a chelating P,N ligand. Structures of Ph3PCHC(NPh)Ph and [NiPh{Ph2PCHC)NPh)Ph}-{Ph3PCHC(NPh)Ph-N}]

Abstract

The complexes [[graphic omitted]Ph)Ph}{Ph₃PCHC(NPh)Ph-N}] and [[graphic omitted]Ph)Ph}(PR₃)](PR₃= PMe₃, PMe₂Ph or PMePh₂) were prepared starting from [Ni(cod)₂](cod = cycloocta-1,5-diene) and the phosphorus ylide Ph₃PCHC(NPh)Ph I in the presence of a tertiary phosphine. Surprisingly, only the first complex was isolated when PPh₃ and P(C₆H₁₁)₃ were used, whereas the other phosphines led to the corresponding PR₃ 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 α-olefins. The molecular structures of I and the first complex have been determined by X-ray diffraction. In the nickel complex the coordination 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)°, respectively.