Ligand exchange reactions between copper(II)- and nickel(II)- chelates of different sulphur- and selenium-containing ligandsIII: Single-crystal ESR study on the mixed-ligand chelate ( n-Bu 4N) [ 63Cu(mnt) (et 2dsc)] and crystal and molecular structure of ( n-Bu 4N) [Ni(mnt) (et 2dsc)

Abstract

A single-crystal ESR study of the mixed-ligand complex tetra - n - butylammonium - (maleonitriledithiolato)(diethyl - di - selenocarbamato)cuprate(II) diamagnetically diluted by the corresponding Ni(II) complex, and the crystal and molecular structure of the host complex determined by a single-crystal X-ray diffraction study, is reported. ( n-Bu 4N)[Ni(mnt)(et 2dsc)] is monoclinic, space group C2/c, with eight molecules in the unit cell; a = 19.932(9) Å, b = 9.597(3) Å, c = 37.580(13) Å and β = 101.32(3)°. Based on the structure the spin Hamiltonian parameters have been calculated from the results of extended Hückel molecular orbital calculations and compared with the experimentally obtained values. The principal axes of the g̃ and the metal hyperfine tensor do not coincide reflecting the large influence of the et 2dsc − ligand for which this behaviour was found to be typical. A comparison between the ESR parameters and the Mulliken spin densities of the mixed-ligand chelate and the corresponding parent complexes shows that in the former one spin density appears to be transfered from the S atoms to the Se atoms of the et 2dsc − part of the complex resulting in an increased CuSe covalency. Back-bonding effects were considered in discussing the bonding properties.