New trinuclear complexes of group 6, 8, and 9 metals with a triply bridging borylene ligand

Abstract

Trinuclear complexes of group 6, 8, and 9 transition metals with a (μ₃-BH) ligand [(μ₃-BH)(Cp*Rh)₂(μ-CO)M′(CO)₅], 3 and 4 (3: M′=Mo; 4: M′=W) and 5–8, [(Cp*Ru) ₃(μ₃-CO)₂(μ₃-BH)(μ₃-E)(μ-H){M′(CO) ₃}] (5: M′=Cr, E=CO; 6: M′=Mo, E=CO; 7: M′=Mo, E=BH; 8: M′=W, E=CO), have been synthesized from the reaction between nido-[(Cp*M)₂B₃H₇] (nido-1: M=Rh; nido-2: M=RuH, Cp*=η⁵-C₅Me₅) and [M′(CO)₅⋅thf] (M′=Mo and W). Compounds 3 and 4 are isoelectronic and isostructural with [(μ₃-BH)(Cp*Co)₂ (μ-CO)M′(CO)₅], (M′=Cr, Mo and W) and [(μ₃-BH)(Cp*Co)₂ (μ-CO)(μ-H)₂M′′H(CO)₃], (M′′=Mn and Re). All compounds are composed of a bridging borylene ligand (B−H) that is effectively stabilized by a trinuclear framework. In contrast, the reaction of nido-1 with [Cr(CO)₅⋅thf] gave [(Cp*Rh)₂Cr(CO)₃(μ-CO)(μ₃-BH)(B₂H₄)] (9). The geometry of 9 can be viewed as a condensed polyhedron composed of [Rh₂Cr(μ₃-BH)] and [Rh₂CrB₂], a tetrahedral and a square pyramidal geometry, respectively. The bonding of 9 can be considered by using the polyhedral fusion formalism of Mingos. All compounds have been characterized by using different spectroscopic studies and the molecular structures were determined by using single-crystal X-ray diffraction analysis.