DIMESITYLBORYL COMPOUNDS. V. ARYL, ETHENYL, ALLENYL, PHENYLETHYNYL AND ALLYL DERIVATIVES

Article abstract of DOI:10.1016/S0022-328X(00)88968-8

Trimesitylborane, five aryldimesitylboranes, ethenyl, allenyl, phenylethynyl and allyldimesitylboranes have been synthesised and characterised by their 1H, 11B and 13C NMR spectra. A set of 13C chemical shift shielding parameters for the dimesitylborynyl group have been obtained which allow the assignment of 13C resonances in meta- and para-substituted aryldimesitylboranes. On the basis of 13C and 11B chemical shift data it is concluded that the unsaturated ligands stabilise these systems by ? electron back-donation to the empty p orbital on boron in the order aryl <*> allenyl < alkenyl < alkynyl. Allyldimesitylborane does not undergo the expected intramolecular allylic rearrangement in solution at temperatures below 140 deg C.