Synthesis of nickel phenyl complexes with new chelating κ2-P,N ligands derived from α-iminoazatriphenylphosphoranes (vol 529, pg 387, 1997)

Reactions of the phosphorus ylide Ph3P=NC(=NPh)Ph (3), conveniently prepared in high yield from Ph3PNLi and ClC(=NPh)Ph, with [Ni(COD)(2)] in the presence of a tertiary phosphine yielded the complexes [NiPh{Ph2PN=C(NPh)Ph} {NPh[=CPh(N=PPh3)]}] (5) and [NiPh{Ph2PN=C(NPh)Ph}(PR3)] (PR3 = PMe3 (6a), PMe2Ph (6b), PMePh2 (6c)) which result from oxidative addition of a P-Ph bond to the Ni(0) centre. When PTol(3) was used, only 5 could be isolated, whereas the other phosphines led to the corresponding complexes 6a-c together with varying amounts Of 5 depending on their steric demand. Reaction of the N-methylated phosphorus ylide Ph3P=N-C[=N(o-C6H4)NMe] (1-methyl-2=(triphenylphosphoranylideneamino)benzimidazole (7)) with [Ni(COD)(2)] in the presence of PTol(3) gave the complex [NiPh{Ph2PN=C[N(o-C6H4)NMe]}(PTol(3))] (9). NO such reaction was observed for the non-methylated analogue Ph3P=N-C[=N(o-C6H4)NH] (2-(triphenylphosphoranylideneamino)benzimidazole (8)), but a dinuclear complex with N,N bridged ligands formulated as [Ni-2{Ph3P=N-C[=N(o-C6H4)N]}(4) (10) was formed. Experiments to study the potential of the nickel compounds as catalysts for ethylene oligomerization were disappointing and only the formation of styrene and minor amounts of low molecular weight linear alpha-olefins was observed. The structure of [Ph3P=NC(=NPh)Ph]. HCl (3 . HCl) has been determined by X-ray diffraction: monoclinic, space group P2(1)/n, 13.137(3), b = 14.942(4), c = 13.9444(4) Angstrom, beta = 90.13(2)degrees, V = 2737.2 Angstrom(3), Z = 4. The structure was solved (direct methods) by using 2209 reflections with I > 3 sigma (I) out of 6028 unique reflections and refined (full-matrix least-squares) to R(F) = 0.048, Rw(F) = 0.068. (C) 1998 Elsevier Science S.A. All rights reserved.