Nickel(II) and palladium(II) complexes of diphenylphosphinoacetone and its enolate

Abstract

Complexes of diphenylphosphinoacetone (HL = Ph₂PCH₂COMe), [NiCl₂(HL)₂]1, [PdCl₂(HL)₂]2 and its enolate [NiL₂]3 and [PdL₂]4, have been synthesized and characterized by ³¹P, ¹H NMR and IR spectroscopy. Single-crystal X-ray diffraction studies of 1–3 reveal square-planar geometry at the central atom. There is a trans arrangement in 1 and 2 and a cis arrangement for 3. A ¹H NMR spin-saturation transfer experiment indicates that the complex 2 exists as a cis–trans equilibrium mixture in CDCl₃ solution. Complex 4 has a structure analogous to that of 3, as revealed by ¹H NMR spectroscopy. Steric reasons for the geometrical preferences are discussed.