Pentachlorophenyl β-carbonylenolate phosphino nickel(II) complexes: Synthesis, full 1H, 31P and 13C NMR characterization and X-ray structure of pentachlorophenyl 1-ethoxy-1,3-butanedionate diphenylmethylphosphino nickel(II)

Abstract

Reaction of the cationic complex[Ni(C 6Cl 5)(CH 3CN)L 2] + (L = PPh 2Me) with β-dicarbonyls (diketones and ethyl-2-oxo-butanoate) in the presence of NEt 3 affords the neutral complexes [Ni(C 6Cl 5)(β-carbonylenolate)L]. A more convenient synthesis of analogous complexes was found in the reaction of trans-[Ni(Cl)(C 6Cl 5)L 2] (L = PPhMe 2, PMe 3) and [Tl(β-carbonylenolate)]derivatives. The isolated complexes have been characterized by 1H, 31P and 13C NMR and IR spectroscopies. They exhibit a square planar geometry in which the β-carbonylenolate acts as O,O′-chelating ligand; complexes with unsymmetrically substituted β-ketoenolates give rise in solution to mixtures of geometrical isomers. A single crystal X-ray structure of the ketoester derivative, [Ni(C 6Cl 5)(CH 3C(O)CHC(O)OEt)(PPh 2Me)], shows that the isomer bearing the ester carbonyl group trans to the phosphine is the only one present in the solid state. The crystal is monoclinic, space group P2 1/ n, Z = 4 and the cell dimensions are a = 13.332(4), b = 23.799(6), c = 8.674(3) Å, β = 97.2(3)°.