Synthesis and structural characterization of isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarboranes stabilized by the agostic bonding interaction

The [7-Me3N-nido-7-CB10H12] (1), after being treated with two molar equiv. of Proton Sponge, reacts with [(η4-C10H12)2Rh2(μ-Cl)2] (2) in benzene–ethanol solution affording two isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarborane complexes, differing in hapticity of the carbocyclic ligand, viz. [2,2-{(2′,3′-η2):(5′-η1)-C10H13}-1-(Me3N)-2,1-closo-RhCB10H10] (3) and [2-{(1′-3′-η3)-C10H13}-1-(Me3N)-2,1-closo-RhCB10H10] (4). Isomeric compounds 3 and 4 were characterized by analytical, multinuclear NMR spectroscopic data as well as by single-crystal X-ray diffraction study, which revealed the existence of an agostic C–H⋯Rh interaction in both the species.