DIMESITYLBORYL COMPOUNDS. IV. SULPHUR DERIVATIVES

Article abstract of DOI:10.1016/S0022-328X(00)84580-5

A series of hydrocarbylthiodimesitylboranes (Mes2BSR) has been synthesized, characterised and their 1H, 11B and 13C NMR data recorded.The steric hindrance induced by the four ortho methyl groups is insufficient to prevent rapid hydrolysis in the air of the B-S bonds in compounds where R = alkyl.However, with the bulkier R = aryl groups hydrolytic stability is achieved.The existence of appreciable boron-sulphur ? back-bonding in these compounds is shown by the presence of non-equivalent mesityl groups in the ambient temperature 1H and 13C NMR spectra.The mechanism which leads to removal of this non-equivalence has a free energy of activation ΔG₇₇^<*> = 76.9+/-0.4 kJ mol^-1 for R = Ph.