RAMAN SPECTRAL STUDY ON THE STRUCTURE OF A HYDROLYTIC DIMER OF THE AQUAVANADIUM(III) ION

The bridging mode of the hydrolytic dimer of aquavanadium(III) has been determined on the basis of its Raman spectra in resonance with the charge-transfer absorption band in the region 550-380 nm. The Raman spectral characteristics of the hydrolytic dimer are very similar to those of [V2O(ttha)]2-, which has been thought to be a mu-oxo dimer. The hydrolytic dimer formed in a 1:1 mixture of H2O-18/H2O-16 shows no bands which correspond to isotopically mixed species. These observations clearly indicate that the hydrolytic dimer of aquavanadium(III) has a mu-oxo bridge rather than a bis(mu-hydroxo) bridge. The Raman band due to the first overtone of the antisymmetric V-O-V stretching is strongly resonance-enhanced as in the case of binuclear mu-oxo molybdenum complexes (Lincoln, S.E.; Loehr, T. M. Inorg. Chem. 1990, 29, 1907).