1,3,2‐Diselenaborolanes with an Annelated Dicarba‐ closo ‐dodecaborane(12) Unit: Synthesis, Molecular Structure and Reactivity

Exchange reactions of 2,2-dimethyl-1,3-diselena-2-silacyclopentane and 2,2,3,3-tetramethyl-1,4-diselena-2,3-disilacyclohexane, as the 4,5- and 5,6-[1,2-dicarba-closo-dodecaborano(12)] derivatives, respectively, with boron trihalides (BCl3, BBr3, BI3) and dichlorides (PhBCl2, iPr2NBCl2) afford the corresponding 1,3,2-diselenaborolanes in essentially quantitative yield. The products were characterized in solution by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 29Si, 77Se), and for two products, in the solid state by X-ray structural analysis. Attempts to synthesize the boron fluoride failed, and the methoxy derivative was obtained in a mixture with a decomposition product. The gas-phase structures of all relevant products were optimized by DFT hybrid methods [RB3LYP/6-311+G(d.p) level of theory], and NMR parameters (shielding constants and spin–spin coupling constants) were calculated. The calculated data compare well with experimental data, both for the structures and the NMR spectroscopic parameters.