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

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