Abstract
The electrophilic abstraction of chloride ion by SbCl5 from diphenylchlorborane in CD3NO2 resulted in a transient species that was followed in situ by 11B and 13C NMR spectroscopy. 11B NMR chemical shift (20.0 ppm) of the species downfield from BF3-etherate reference was indicative of the formation of diphenylboron cation stabilized by O donor of two nitromethane molecules, i.e., solvated diphenylboron cation. Addition of two equivalent of pyridine to the solvated cationic species moved 11B NMR chemical shift to 11.0 ppm, which is typical for four coordinate boronium salt. However, the reaction of diphenylchlorborane and one equivalent of pyridine in CD3NO2 gave only adduct species showing similar 11B chemical shift of boronium salt (sp3). Reaction of this adduct with SbCl5 as chloride acceptor caused 11B chemical shift considerably downfield (31 ppm), resulting in three coordinate diphenylboron cation with N-ligand of pyridne (sp2). This borenium cation was then treated with one equivalent of pyridine to give the above boronium salt. An ab initio calculation of the 11B chemical shift has been done by GIAO-HF/6-311+G(2d,p)//B3LYP/6-31+G(d)). The experimental 11B chemical shift was in good agreement with the calculation result.
