Fused metallaborane clusters of group 9 and 8 transition metals

Abstract

Building on our earlier results, the condensation of rhodium polychlorides with borane reagents (LiBH₄·thf, BH₃·thf, BHCl₂·SMe₂ etc.), we continue to explore the chemistry of the same system with metal carbonyl compounds. As a result, the reaction of [(Cp*Rh)₂B₂H₆], generated from fast metathesis of [Cp*RhCl₂]₂ and LiBH₄, with heavier group 8 metal carbonyl compounds, yielded [(Cp*Rh)₂B₄H₄Rh{Cp*RhB₃H₈}], 1, [(Cp*Rh)B₃H₇{Ru(CO)₂}(Cp*RhCO)₂], 2 [(Cp*Rh)₂B₃H₃{Ru(CO)₃}₂], 3 and [(Cp*Rh)₂{Os₄(CO)₁₂}(B)H], 4. Further, these reaction also generated two mixed-metal tetrahedral hydrido clusters [(Cp*Rh){Os(CO)₃}₃(μ-H)₄], 5 and [(Cp*Rh)₂{Os(CO)₃}₂ (μ-CO) (μ-H)₂], 6 as minor products. Compound 1 is an octahedra and a square pyramid fused cluster, whereas for 2 a square pyramid and a triangle are fused through a vertex. Both 1 and 2 follow Mingos's formalism for fused clusters. Cluster 4 is an interstitial boride composed of one boron, two rhodium and four osmium atoms. Based on its compositions, compound 4 is a rare example of heteronuclear borides. All the compounds have been characterized by IR, ¹H, ¹¹B, ¹³C NMR spectroscopy in solution and the solid state structures were established by crystallographic analysis of 1–5.