Crystal polarised spectra, and electronic structures, of some pseudotetrahedral cobalt(II) complexes with ‘soft’ bonding ligands

Abstract

The crystal polarised spectra of some pseudotetrahedral Co^II complexes having chromophores [CoS₂Cl₂] and [CoP₂X₂](X = Br^–, I^–), have been recorded. The spectra may be assigned assuming an effective C_2ν symmetry and spin–orbit coupling is found to be less important than the low-symmetry ligand field in modifying the electronic structure derived from T_d symmetry. The sequence of components derived from T_d symmetry is found to be: ⁴T₁(F) : B₁ < A₂ < B₂; ⁴T₁(P) : B₂ < A₂ < B₁. Crystal-field calculations fit the observed spectra only if parameters of the low symmetry components are treated as merely empirical parameters. Qualitative σ- and π-bonding parameters for the different donor ligands are derived and compared.