SYNTHESIS OF NICKEL PHENYL COMPLEXES WITH NEW CHELATING KAPPA(2)-P,N LIGANDS DERIVED FROM ALPHA-IMINOAZATRIPHENYLPHOSPHORANES

Reactions of the phosphorus ylide Ph3P=NC(=NPh)Ph (3), conveniently pr epared in high yield from Ph3PNLi and ClC(=NPh)Ph, with [Ni(COD)(2)] i n the presence of a tertiary phosphine yielded the complexes [NiPh{Ph2 PN=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 a ddition of a P-Ph bond to the Ni(0) centre. When PTol(3) was used, onl y 5 could be isolated, whereas the other phosphines lead to the corres ponding complexes 6a-c together with varying amounts of 5 depending on their steric demand. Reaction of the N-methylated phosphorus ylide Ph 3P=N-C[=N(o-C6H4)NMe] l-2-(triphenylphosphoranylideneamino)benzimidazo le (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 obser ved for the non-methylated analogue Ph3P=N-C[=N(o-C6H4)NH] (2-(triphen ylphosphoranylideneamino)benzimidazole (8)), but a dinuclear complex w ith N,N bridging ligands formulated as [Ni-2{Ph3P=N-C[=N(o-C6H4)N]}] ( 10) was formed. Experiments to study the potential of the nickel compo unds as catalysts for ethylene oligomerization were disappointing and only the formation of styrene and minor amounts of low molecular weigh t 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, a=13.137(3), b=14.942(4), c=13.944(4)Angstrom, b eta=90.13(2)degrees, V=2737.2 Angstrom(3), Z=4. The structure was solv ed (direct methods) by using 2209 reflections with I> 3 sigma(I) out o f 6028 unique reflections and refined (full-matrix least-squares) to R (F)=0.048, Rw(F)=0.068.