Ligand exchange reactions between copper(II)- and nickel(II)-chelates of different sulphur- and selenium-containing ligands

Abstract

A single-crystal E.S.R. and multi-nuclear ENDOR study of the mixed ligand complex tetra-n-butylammonium(maleonitriledithiolato)(monoethyldithiophosphato)cuprate(II), diamagnetically diluted by the corresponding Ni(II) complex, and the crystal structure of the host complex are reported. n-Bu4N[Ni(mnt)(HEtdtp)].0·7 acetone is triclinic, space group P1, Z = 2 with a = 9·029(2), b = 13·432(4), c = 17·246(5) Å, α = 108·9(1), β = 90·2(1) and γ = 109·4(1)°. The spin-hamiltonian parameters are calculated from the results of an extended Hückel molecular orbital calculation. The experimental g-tensor and the copper and the four sulphur hyperfine coupling tensors are reporduced well. The almost isotropic and unexpectedly large coupling of the phosphorous atom is negative, which can be understood qualitatively from a spin polarization mechanism. The hyperfine coupling tensors of eight protons, three of the acetone molecule, four of the tetra-n-butylammonium cation and one intramolecular one, could be determined. The E.S.R. linewidths are unusually small for Cu complexes. Unresolved proton hyperfine interactions are found to give the largest contribution.