Five-co-ordination with ‘hybrid’ ligands. Part VII. Cobalt(II) and nickel(II) complexes with asymmetric tripod ligands having N2OP, N2SP, and NOAs2 donor sets

Abstract

The asymmetric ‘tripod’ ligands N-[2-(diphenylphosphino)ethyl]-N-(2-methoxyethyl)-N′N′- diethylthylenediamine (I; donor set N2OP) and N-[2-(diphenylphosphino)ethyl)-N-[2-(methylthio)ethyl]-N′N′-diethylethylenediamine (II; donor set N2SP) form cobalt(II) and nickel(II) complexes with general formula [MLX]BPh4(X = halogen or NCS). The cobalt(II) complexes are high-spin and five-co-ordinate, probably trigonal bipyramidal, both in the solid state and in solution. The [NiLX]BPh4 complexes with L =(I), X = l or NCS are low-spin and probably five-co-ordinate in the solid state with a distorted square-pyramidal stereochemistry. All the other nickel complexes are thought to have a square-planar structure with the ligand L being terdentate with an NNP donor set. The complex [Ni(NOAs2)l]BPh4 derived from the ligand NN-bis-(2-diphenylarsinoethyl)-2-methoxyethylamine (III; donor set NOAs2) is accorded a five-co-ordinate, ‘elongated’ square-pyramidal structure.