Thermal Conversion of closo−1,2-(SiMe3)2−1,2-C2B4H4 to closo-1,6-(SiMe3)2−1,6-C2B4H4: Structure Determination by Ab Initio Calculations, Gas-Phase Electron Diffraction, and Low-Temperature X-Ray Diffraction

closo−1,2-(SiMe3)2−1,2-C2B4H4 undergoes thermal conversion to 1,6-(SiMe3)2−1,6-C2B4H4. The reaction pathway was monitored by 11B NMR spectroscopy. The structures of the 1,2- and 1,6-isomers were optimized at the HF/6-31 G* ab initio level. Gas-phase electron diffraction studies for both isomers are reported, as well as low-temperature X-ray crystal structure determinations. Comparison of calculated structural data with the data obtained experimentally shows good agreement between theory and experiment.