Chemistry of vanadaboranes: synthesis, structures, and characterization of organovanadium sulfide clusters with disulfido linkage

Abstract

Vanadaborane, [(CpV)₂(B₂H₆)₂] (Cp = η⁵-C₅H₅), 1 reacts with elemental sulfur to afford the hexasulfide cluster [(CpV)₂S₄ (μ-η¹-S₂)], 2 in high yield. Compound 2 is a notable example of an organovanadium sulfide cluster in which the [V₂S₄] atoms define a bicapped tetrahedron framework, with one μ-η¹-S₂ ligand bridged the two (CpV) moieties. The sulfur atom in [V₂S₄] core in 2 is a four-skeletal-electron donor isoelectronic with the BH3 unit; therefore, the replacement of boron hydride in 1 by four sulfur atoms necessitates the formation of a bicapped tetrahedron [V₂S₄] framework. Furthermore, this is the only reported example of a bimetallic hexasulfide cluster containing vanadium. Pyrolysis of 1 with bis-chalcogenide ligands such as Ph₂S₂ and Bz₂Se₂ (Bz = PhCH₂), results in the formation of substituted vanadahexaboranes [(CpV)₂B₄H_12−xL_x], 3−5 (3: L = SPh: x = 3; 4: L = SPh, x = 2; 5: L = SeBz: x = 1) in modest yield. All these new compounds have been characterized by mass, ¹H, ¹¹B, ¹³C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of compounds 2−5.