Ligand Hyperfine Interactions in Molybdenyl and Chromyl Halide Complexes

Ligand superhyperfine interactions due to 35,37Cl and 19F have been observed in the ESR spectra of MoOCl52−, MoOF52− and CrOF52−. The presence of both isotropic and anisotropic ligand hyperfine splittings indicates considerable covalency in these complexes. The bonding coefficients, which have been calculated with resonable accuracy, reveal moderately strong in-plane π bonding involving the metal dxy orbital and the ligand py orbital. The spin–orbit interaction of the halide ligand is shown to be important in determining the g values. A configuration-interaction treatment has been used to account for the spin densities in the ligand px and s orbitals. The ESR spectra show that in solutions of KCrOF4 in aqueous hydrofluoric acid two species, CrOF4− and CrOF52−, are present.