Synthesis and structural characterization of group 5 dimetallaheteroboranes

Treatment of group 5 metal polychlorides such as [CpnMCl4−x] (M = Nb: n = 1, x = 0; M = V: n, x = 2), (Cp = η5−C5H5) with [LiBH4·THF] followed by thermolysis in presence of diphenyl dichalcogenide ligands, E2Ph2 (E = Se or Te) yielded dimetallaheteroborane clusters [(CpNb)2BH(Se)4], 1 and [(CpV)2B3H9(μ3-Te)], 2 in modest yields. Compound 1 can be considered as an edge fused cluster in which a trigonal bipyramidal unit [Nb2Se2B] has been fused with a tetrahedral core [Nb2Se2] by means of a common [Nb2] edge. Compound 2 can be described as a dimetallaheteroborane built from two edge-fused V2B2 tetrahedra, in which one of the BH3 units is replaced by an isoelectronic Te ligand. All the compounds have been characterized by mass spectrometry, 1H, 11B, 13C, 51V and 77Se NMR spectroscopy. In addition the geometry of compound 1 has been established by crystallographic analysis.