Cobalt(II) complexes with trimethylarsine oxide and trimethylarsine sulphide

Abstract

Trimethylarsine oxide and trimethylarsine sulphide both form tetrahedral complexes [CoL₄](ClO₄)₂, CoL₂Cl₂, and CoL₂Br₂. In the perchlorate complexes the two ligands produce similar crystal-field splitting energies, but the lower β values of the sulphide complexes and the higher intensities of their spectral bands point to their greater covalent character. The magnetic moment of [Co(Me₃AsS)₄](ClO₄)₂ is significantly lower than that of [Co(Me₃AsO)₄](ClO₄)₂, which is again considered evidence for this difference in the metal–ligand bonding. Metal–ligand vibrations have been assigned for the cobalt and corresponding zinc complexes. These frequencies are consistently lower for the zinc compounds.