Electronic absorption spectra of some oxovanadium(IV) compounds
- 1 January 1980
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 4,p. 667-674
- https://doi.org/10.1039/dt9800000667
Abstract
Single-crystal polarised electronic absorption spectra at 298 and 5 K, in the range 5 000–30 000 cm–1, of [VOX2(tmu)2](tmu = tetramethylurea, X = Cl or Br), [NEt4]2[VOCl4], and [AsPh4]2[VO(NCS)4], and similar spectra of poly(dimethylsiloxane) mulls of [VOCl2(tmtu)2], [VOCl2(tppo)2], [VOCl2(hmpa)2], K3[VO(CN)5], [NH4]3[VOF5], and [NMe4]2[VO(NCS)4(OH2)](tmtu = tetramethylthiourea, tppo = triphenylphosphine oxide, and hmpa = hexamethylphosphoramide) are reported. The absorption bands have been assigned based on a combination of their observed polarisation, relative intensities, vibrational fine structure, and changes in positions with changes in the in-plane ligands. For the five-co-ordinate complexes all of the expected d–d type transitions occur below 30 000 cm–1, the electronic bands at 5 K for (3dxy*)→(3dxz*,3dyx*) being in the range 12 860–15 100 cm–1, for (3dxy*)→(3dz2*) in the range 21 000–22 000 cm–1, whilst the (3dxy*)→(3dx2–y2*) transition varies in energy as expected from the changes in the in-place ligands. For the six-co-ordinate complexes only the (3dxy*)→(3dxz*, 3dyz*) and (3dxy*)→(3dx2y2*) transitions are observed below 30 000 cm–1. It is suggested that in these latter complexes the (3dxy*)→(3dz2*) transition lies above 30 000 cm–1 its energy being increased due to an increase in the ligand-field strength along the molecular z axis.Keywords
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