Phosphorus Analogues of [Ni(bpy)]: Synthesis and Application in Carbon-Halogen Bond Activation.

The neutral, homoleptic pyridylphosphininenickel(0) complex [Ni(2-Py-4,6-Ph-PCH)] () has been obtained by reaction of the formal Ni(0) source [(IPr)Ni(HC═CHSiMe)] with 2 equiv of 2-(2'-pyridyl)-4,6-diphenylphosphinine (). Compound can be oxidized both electrochemically and through the use of ferrocenium salts, to afford the corresponding Ni(I) complexes []BF, [(THF)]PF, and [](BAr). The structures of these salts reveal an interesting dependence on the nature of the anion. While []BF and [(THF)]PF show trigonal-bipyramidal coordination of Ni in the solid state, [](BAr) exists as a dinuclear Ni(I) complex and possesses a bridging phosphinine moiety in a rare μ mode. Reactions of with halobenzenes highlight the noninnocent behavior of the aromatic phosphinine ligand, leading to the formation of oxidized Ni complexes but not to classical oxidative addition products. The reaction of with bromobenzene affords the λ phosphinine and the bipyramidal Ni(I) complex []Br, whereas a more unconventional oxidation product is formed from the reaction of and iodobenzene.