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.