Synthesis and Reactivity of the CO<sub>2</sub> 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 (<b>1</b>) and a secondary amine (such as HN<i>i</i>Pr<sub>2</sub> or HNEt<sub>2</sub>) readily react with CO<sub>2</sub> at room temperature to afford ammonium carbamatoborate salts <b>2</b>. When the reaction was carried out at 80 °C, carbamate boryl esters <b>3</b> were obtained with release of 1 equiv of H<sub>2</sub>. The <i>i</i>Pr-substituted carbamate boryl ester <b>3a</b> can function as an intramolecular FLP to activate H<sub>2</sub>, affording ammonium borylformate salt <b>4a</b> and formamide adduct <b>5a</b>. Two reaction pathways leading to the formation of <b>4a</b> and <b>5a</b> are proposed.