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)2 B3 H7 ] (nido-1: M=Rh; nido-2: M=RuH, Cp*=η(5) -C5 Me5 ) 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)2 M''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)2 Cr(CO)3 (μ-CO)(μ3 -BH)(B2 H4 )] (9). The geometry of 9 can be viewed as a condensed polyhedron composed of [Rh2 Cr(μ3 -BH)] and [Rh2 CrB2 ], 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.