Olefin–Borane “van der Waals Complexes”: Intermediates in Frustrated Lewis Pair Addition Reactions

Abstract

The nature of the borane–olefin interactions that take place prior to frustrated Lewis pair addition reactions has been probed employing a Lewis acidic borane tethered to a vinyl group through an alkyl chain. 1H{19F} HOESY spectral data obtained at −50 °C demonstrated the spatial proximity of the boryl and vinyl groups and computational data support the initial formation of a van der Waals borane–olefin complex. Such species serve as intermediates undergoing facile addition reactions with phosphine bases to afford cyclic zwitterionic products