Preparation of bis(phosphine)bis(selenocarboxylato)-nickel(II), -palladium(II) and -platinum(II) complexes and their crystal structure analysis

A series of bis(triorganophosphine)bis(selenocarboxylato)-nickel(II) 3, -palladium(Ir) 4 and -platinum(II) 5 complexes have been synthesised from the reaction of sodium selenocarboxylates 1 or O-silyl selenocarboxylates 2 with the corresponding bis(phosphine)metal dichloride in good to high yields and have been characterized by H-1, C-13, P-31 and Se-77 NMR spectroscopy and elemental analysis. Additionally [M(4-MeC(6)H(4)COSe)(2)(PEt(3))(2)] (M = Ni 3d, Pd 4d or Pt 5b) have been crystallographically characterized and reveal four-co-ordinate planar structures with each of the two selenocarboxylate and phosphine ligands lying trans. The carbon-oxygen bond lengths [1.209(6), 1.203(8) and 1.212(6) Angstrom] of the selenocarboxylate ligand of 3d, 4d and 5d show values typical of a carbon-oxygen double bond; co-ordination of the carbonyl oxygen to the metal is not observed.