Substitution at B-H vertices of group 5 metallaborane clusters

Thermolysis of an in situ generated intermediate which was formed by the reaction of [Cp*VCl2]3 (Cp* = η5-C5Me5) and LiBH4. THF with excess of BH3.THF (THF = tetrahydrofuran) led to the formation of a novel dioxadivandaborane, [(Cp*V)2(OBH3)2], 2 along with divanadaborane [(Cp*V)2(B2H6)2], 1. In an attempt to functionalize the terminal B-H vertices by different aryl chalcogenides, 1 was thermolyzed with dinaphthyl diselenide, [Nap2Se2] and dimesityl diselenide, [Mes2Se2], leading to the formation of persubstituted divanadaboranes, [(Cp*V)2{B2H4(SeNap2)}2], 3 and [(Cp*V)2{B2H4(SeMes2)}2], 7. All these compounds were fully characterized with the help of mass spectrometry and 1H, 11B{1H} and 13C{1H} NMR spectroscopy and the dioxadivandaborane species 2 was additionally characterized by X-ray diffraction analysis. Density Functional Theory (DFT) calculations show geometries in agreement with the structural determinations. The reduction in the HOMO-LUMO gap due to the introduction of chalcogenide ligands in 2, 3 and 7 is in respectable agreement with their UV–Vis absorption spectra.