Metal–ligand bonding in some vanadium compounds: a study based on X-ray emission data

Abstract

K _α And K_βX-ray emission spectra of V (metal), [V(pd)₃](pd = pentane-2,4-dionate), VF₃, VO₂, V₂O₅, [VO][SO₄], [NH₄][VO₃], and [NH₄][V₃O₈] are reported. It is argued that peaks of higher energy than K_β1,3 are due to transitions involving molecular orbitals with Vp character rather than V 3d. The relative intensities and emission energies of the K_β1,3, K_β^″, and K_β2,5 peaks are discussed using m.o. theory. The K_β^″ : K_β2,5 relative intensity is much higher than for comparable main-group compounds; this is probably due to the presence of 3p character in the orbital that gives rise to K_β^″; 3p character also enhances the intensity of K_β2,5. Changes in peak positions and relative intensities associated with the oxidation state of vanadium can be qualitatively rationalised by a consideration of 4p character alone. It is suggested that the K_β^‴ peak observed at higher energies (+15 eV) than K_β2,5 is formed by relaxation of an electronically excited species (resonance radiation).