Five-co-ordination with ‘hybrid’ ligands. Part IV. Cobalt(II) and nickel(II) complexes with terdentate ligands containing phosphorus and nitrogen or sulphur as donor atoms

Abstract

The terdentate ligand bis-(2-diphenylphosphinoethyl)amine (I) and the related N-alkyl-substituted ligands where the alkyl group is either methyl (II) or cyclohexyl (III) have been synthesised. Theygive with nickel (II) halides complexes of general formulas NiLX₂(L = I, II, or III; X = Br, l), [NiLX]₂[NiX₄](L = I or II; X = Cl, Br), and [NiLX]B(C₆H₅)₄(L =C; X = Cl, Br, l). With cobalt(II) halides, complexes of general formula CoLX₂(L = I, II, or III; X = Br, l) have been obtained. The nickel complexes are either low-spin five-co-ordinate or square-planar, depending on the bulkiness of the R group, but in solution they give only square-planar species [NiLX]⁺. The stereochemistry of the cobalt complexes changes from five-co-ordinate to tetrahedral with increasing bulkiness of the R group. Some similar complexes with the already known bis(diphenylphosphinoethyl) sulphide ligand have also been characterized.