Unusual 1,1-Hydroboration Route to a Reactive Unsaturated Vicinal Frustrated Phosphane/Borane Lewis Pair

Abstract

Piers’ borane HB(C6F5)2 reacted with the alkyne Mes2P–C≡C–SiMe3 by a rarely observed 1,1-hydroboration reaction under kinetic control to give the unsaturated vicinal frustrated phosphane/borane Lewis pair 6, featuring both the PMes2 and SiMe3 groups at the same carbon atom C1. Compound 6 is a reactive P/B FLP which splits dihydrogen under mild conditions. Thermolysis at 100 °C converts it to the markedly less reactive P/B FLP regioisomer which bears the −SiMe3 substituent at carbon atom C2 adjacent to the B(C6F5)2 group. Most new compounds were characterized by X-ray diffraction.