Synthesis, characterization and electronic structures of Rh and Co analogs of Decaborane-14

Abstract

We report the synthesis, isolation and structural characterization of several crystalline, moderately air stable nido-metallaboranes which represent novel metal rich open cage systems. The reaction of [Cp*CoCl]₂, (Cp* = η⁵-C₅Me₅), with [LiBH₄·thf] in toluene at −78 °C, followed by thermolysis with [BH₃·thf] in boiling toluene yielded clusters, [(Cp*Co)₃B₆H₈O] (1) and [(Cp*Co)₂B₈H₁₁Me] (2). Under the similar reaction condition, [Cp*RhCl₂]₂ yielded [(Cp*Rh)₃B₇H₁₁] (3) and [(Cp*Rh)₂B₈H₁₂] (4). All the new compounds, 1–4 have been characterized by elemental analysis, IR, ¹H, ¹¹B, ¹³C NMR spectroscopy, and the geometric structures were unequivocally established by X-ray diffraction analysis of compound 1–4. Quantum chemical calculation by using density functional theory method is implemented on model compounds 1′–4′ (1′–4′ are the Cp analogs of 1–4 respectively, Cp = C₅H₅) and yields geometries in agreement with the X-ray detaermined geometries. Large HOMO–LUMO gaps are in tally with the higher stabilities of 1′ and 3′.