Synthesis and Reactivity of the CO2 Adducts of Amine/Bis(2,4,6-tris(trifluoromethyl)phenyl)borane Pairs

Frustrated Lewis pairs (FLPs) comprised of bis­(2,4,6-tris­(trifluoromethyl)­phenyl)­borane (1) and a secondary amine (such as HNiPr2 or HNEt2) readily react with CO2 at room temperature to afford ammonium carbamatoborate salts 2. When the reaction was carried out at 80 °C, carbamate boryl esters 3 were obtained with release of 1 equiv of H2. The iPr-substituted carbamate boryl ester 3a can function as an intramolecular FLP to activate H2, affording ammonium borylformate salt 4a and formamide adduct 5a. Two reaction pathways leading to the formation of 4a and 5a are proposed.