Five-co-ordination with ‘hybrid’ ligands. Part VI. Cobalt(II) and nickel(II) complexes with a quadridentate tripod ligand having a NOPP donor set

Abstract

The quadridentate ‘tripod’ ligand NN-bis-(2-diphenylphosphinoethyl)-2-methoxyethylamine (NOP2 donor set) forms cobalt(II) and nickel(II) complexes with the general formulae [MLX]Y (X = Cl, Br, I, NCS; Y = Br, I, PF6, BPh4), [CoLX]2[CoX4](X = Br, I), and CoLX2(X = Cl, Br, I, NCS). The complex cations [NiLX]+ are low-spin with an ‘elongated’ square-pyramidal structure. The [CoLX]+ complexes are all five-co-ordinate. When X = halogen the complexes are high-spin distorted trigonal-bipyramidal; the NCS derivative is low-spin with ‘elongated’ square-pyramidal geometry. In the CoLX2 complexes the ligand acts either as terdentate (donor set NP2) or as bidentate (donor set P2); this flexidentate behaviour gives rise to various structures as well as to different spin states. Lengthening of the OMe arm in the related ligand NN-bis-(2-diphenylphosphinoethyl)-3-methoxyprpropylamine (N–OP2) appears to prevent co-ordination of the ethereal oxygen.