Synthesis and structural characterization of new divanada- and diniobaboranes containing chalcogen atoms.

The reaction of [Cp(n)MCl(4-x)] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η(5)-C(5) H(5)) with LiBH(4)⋅THF followed by thermolysis in the presence of dichalcogenide ligands E(2)R(2) (E=S, Te; R=2,6-(tBu)(2)-C(6)H(2)OH, Ph) and 2-mercaptobenzothiazole (C(7)H(5)NS(2)) yielded dimetallaheteroboranes [{CpV(μ-TePh)}(2)(μ(3) -Te)BH⋅thf] (1), [(CpV)(2)(BH(3)S)(2)] (2), [(CpNb)(2)B(4)H(10)S] (3), [(CpNb)(2)B(4)H(11)S(tBu)(2)C(6)H(2)OH] (4), and [(CpNb)(2)B(4)H(11)TePh] (5). In cluster 1, the V(2)BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge-fused V(2)BS tetrahedron clusters. Cluster 3 can be considered as an edge-fused cluster in which a trigonal-bipyramidal unit (Nb(2)B(2)S) has been fused with a tetrahedral core (Nb(2)B(2)) by means of a common Nb(2) edge. In addition, thermolysis of an in-situ-generated intermediate that was produced from the reaction of [Cp(2)VCl(2)] and LiBH(4)⋅THF with excess BH(3)⋅THF yielded oxavanadaborane [(CpV)(2)B(3)H(8)(μ(3)-OEt)] (6) and divanadaborane cluster [(CpV)(2)B(5)H(11)] (7). Cluster 7 exhibits a nido geometry with C(2v) symmetry and it is isostructural with [(Cp*M)(2)B(5)H(9+n)] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η(5)-C(5)Me(5)). All of these new compounds have been characterized by (1)H NMR, (11)B NMR, and (13)C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds 1-4, 6, and 7.