Preparation of five-membered nickelacycles with anionic C-N-N' terdentate ligands. X-ray crystal structure of [NiCl{2-(CH=NCH(2)CH(2)NMe(2))-3-ClC6H3}]

The five-membered metallacycles [Ni(C-N-N')X] have been prepared by oxidative addition of o-halo-substituted imines derived from N,N-dimethylethylienediamine, C(6)R(n)H(5-n)CH=NCH(2)CH(2)NMe(2) to [Ni(COD)(2)]. The molecular structure of [NiCl{2-(CH=NCH(2)CH(2)NMe(2))3-ClC6H3}] has been determined by a single-crystal X-ray crystallographic study. Some ionic compounds [Ni(C-N-N')L]BF4 (L = NCMe, heterocyclic amines) were also obtained. The Ni-C bond of these complexes is inert toward insertion reactions of ethylene or PhC=CPh. The action of [Ni(COD)(2)] on the diamines C(6)R(n)H(5-n)CH(2)N(Me)CH(2)CH(2)NMe(2) affords highly insoluble organonickel derivatives, which by reaction with aromatic amines (L) in the presence of TlBF4 lead to the ionic derivatives [Ni(C-N-N')L]BF4. The stabilization of organometallic Ni(III) compounds using CuCl2 as oxidant was not achieved. Coordination compounds [NiClBr(N'-N)], where N-N' = 2-ClC6H4CH2N(Me)CH(2)CH(2)NMe(2), were formed probably by reductive elimination of Ni(III) species followed by reoxidation to Ni(II).