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.