Metallaheteroborane clusters of group 5 transition metals derived from dichalcogenide ligands

Treatment of group 5 metal polychlorides such as, [CpnMCl4-x] (M = V: n, x = 2; M = Nb: n = 1, x = 0), or [Cp∗TaCl4] (Cp = η5–C5H5, Cp∗ = η5-C5Me5), with [LiBH4·THF] followed by thermolysis in the presence of diphenyl diselenide yielded metallaheteroborane clusters [{CpV(μ-SePh)}2(μ-Se)], 1 [(CpNb)2B4H9(μ-SePh)], 2 and [(Cp∗Ta)2B4H11(SePh)], 3 in modest yields. Compound 1 is an organovanadium selenolato cluster in which two (CpV) moieties bridged by (μ-Se) and two (μ-SePh) ligands. Compound 2 exhibits a bicapped tetrahedral core with one (μ-SePh) ligand. 3 is a tantalahexaborane cluster in which one of the terminal BH protons is substituted by SePh. Compounds 1–3 have been characterized by mass spectrometry, 1H, 11B, 13C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis of 1–3.