Degradation Chemistry of Dimetallaboranes, [(Cp*M)₂B₅H_9+x] with [Ph₂Se₂] (x = 2 or 0, M = V or Cr)

Abstract

The synthesis and structural characterization of new divanadaborane clusters are reported. The pressure tube thermolysis of an intermediate formed by the reaction of [(Cp*VCl 2 ) 3 ] with [LiBH 4 •THF] and [BH 3 •THF] in diglyme at 160 °C yielded 6-sep, 7-vertex oblato-nido cluster, [(Cp*V) 2 B 5 H 11 ],2 (Cp* = pentamethyl-η 5 -cyclopentadienyl). In an attempt to test the reactivity of this cluster with chalcogenide ligands, thermolysis of 2 with [Ph 2 E 2 ] (E = S, Se, or Te) in toluene was carried out. While the reaction of 2 with [Ph 2 Se 2 ] resulted in the formation of [(Cp*V) 2 B 4 H 8 (SePh)(μ-SePh)], 3, via cluster degradation reaction, [Ph 2 S 2 ] and [Ph 2 Te 2 ] did not generate analogous clusters. Compound 3 is an example of a tetraborane cluster being stabilized by two SePh fragments, one bridging the two Cp*V fragments while the other forming a terminal bond with one of the boron atoms. In an attempt to explore the cluster degradation reaction with analogous group 6 metallaborane [(Cp*Cr) 2 B 5 H 9 ], 5, we treated it with [Ph 2 Se 2 ] that led to the formation of terminally substituted [(Cp*Cr) 2 B 5 H 7 (SePh) 2 ], 6. All the clusters were characterized by using various spectroscopic studies and X-ray diffraction analysis. Quantum chemical calculations using density functional theory methods were carried out to gain more insight into the bonding and electronic structure of 3 and 6.