B–H Functionalization of Hydrogen-Rich [(Cp*V)2(B2H6)2]: Synthesis and Structures of [(Cp*V)2(B2X2)2H8] (X = Cl, SePh; Cp* = η5-C5Me5)

Abstract

We have recently reported the perchlorinated diniobaborane species [(Cp*Nb)2(B2H4Cl2)2] from [(Cp*Nb)2(B2H6)2] using CCl4 as a chlorinating agent. In an attempt to isolate the vanadium analogue, we have isolated [(Cp*V)2(B2H6)2] (1) from the reaction of (Cp*VCl2)3 with [LiBH4·THF] followed by thermolysis with excess [BH3·THF]. Subsequently, the thermolysis of 1 with CCl4 for a prolonged period of time afforded the perchlorinated divanadaborane [(Cp*V)2(B2H4Cl2)2] (2) along with the formation of the bichlorinated divanadaborane [(Cp*V)2(B2H5Cl)2] (3) and trichlorinated divanadaborane [(Cp*V)2(B2H4Cl2)(B2H5Cl)] (4). Similarly, in order to functionalize the terminal B–H by a {SePh} group, thermolysis of 1 was carried out with Ph2Se2, which yielded the persubstituted divanadaborane [(Cp*V)2{B2H4(SePh)2}2] (5) in parallel to the formation of [(Cp*V)2{B4H11(SePh)}] (6). Compound 5 is very fascinating in that all of the terminal B–H hydrogens of 1 have been substituted by {SePh} ligands. All of the compounds have been characterized by 1H, 11B, and 13C NMR spectroscopy, mass spectrometry, IR spectroscopy, and single-crystal X-ray analysis. Density functional theory (DFT) and TD-DFT calculations provided a further understanding regarding the electronic structures, bonding, and electronic transitions of these persubstituted vanadaborane species.