Intramolecular Frustrated Lewis Pair with the Smallest Boryl Site: Reversible H-2 Addition and Kinetic Analysis

摘要

Ansa-aminoborane 1 (ortho-TMPC6H4BH2; TMP=2,2,6,6-tetramethylpiperid-1-yl), a frustrated Lewis pair with the smallest possible Lewis acidic boryl site (BH2), is prepared. Although it is present in quenched forms in solution, and BH2 represents an acidic site with reduced hydride affinity, 1 reacts with H-2 under mild conditions producing ansa-ammonium trihydroborate 2. The thermodynamic and kinetic features as well as the mechanism of this reaction are studied by variable-temperature NMR spectroscopy, spin-saturation transfer experiments, and DFT calculations, which provide comprehensive insight into the nature of 1.