Synthesis of nickel phenyl complexes with new chelating kappa(2)-P,N ligands derived from alpha-iminoazatriphenylphosphoranes (vol 529, pg 387, 1997)

Reactions of the phosphorus ylide Ph3P=NC(=NPh)Ph (3), conveniently prepare d in high yield from Ph3PNLi and ClC(=NPh)Ph, with [Ni(COD)(2)] in the pres ence of a tertiary phosphine yielded the complexes [NiPh{Ph2PN=C(NPh)Ph} {N Ph[=CPh(N=PPh3)]}] (5) and [NiPh{Ph2PN=C(NPh)Ph}(PR3)] (PR3 = PMe3 (6a), PM e2Ph (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, wher eas the other phosphines led to the corresponding complexes 6a-c together w ith 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=(tripheny lphosphoranylideneamino)benzimidazole (7)) with [Ni(COD)(2)] in the presenc e of PTol(3) gave the complex [NiPh{Ph2PN=C[N(o-C6H4)NMe]}(PTol(3))] (9). N O such reaction was observed for the non-methylated analogue Ph3P=N-C[=N(o- C6H4)NH] (2-(triphenylphosphoranylideneamino)benzimidazole (8)), but a dinu clear complex with N,N bridged ligands formulated as [Ni-2{Ph3P=N-C[=N(o-C6 H4)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 li near alpha-olefins was observed. The structure of [Ph3P=NC(=NPh)Ph]. HCl (3 . HCl) has been determined by X-ray diffraction: monoclinic, space group P 2(1)/n, 13.137(3), b = 14.942(4), c = 13.9444(4) Angstrom, beta = 90.13(2)d egrees, V = 2737.2 Angstrom(3), Z = 4. The structure was solved (direct met hods) by using 2209 reflections with I > 3 sigma (I) out of 6028 unique ref lections and refined (full-matrix least-squares) to R(F) = 0.048, Rw(F) = 0 .068. (C) 1998 Elsevier Science S.A. All rights reserved.