Combination of Arsines and Tris(pentafluorophenyl)borane Toward Frustrated Lewis Pair

Various combinations of Lewis acids and bases, particularly frustrated Lewis pairs (FLPs), have been investigated for their distinctive reactivities. Nevertheless, to date, no systematic study of arsine-borane Lewis pairs has been reported. In this study, tertiary arsines with different degrees of steric hindrance and electron-donating abilities were used. Depending on their steric and electronic properties, arsines form classical Lewis adducts, FLPs, or arsonium borate adducts with tris(pentafluorophenyl)borane (B(C₆F₅)₃). Experimental and computational analyzes revealed that trimesitylarsine and B(C₆F₅)₃ form an encounter complex in solution, which is referred to as an FLP adduct. Furthermore, the arsine-borane pairs react with phenylacetylene and diphenyl disulfide to afford the corresponding arsonium borate adduct and thioarsonium thioborate salt, respectively. The structures of the products were characterized using single-crystal X-ray diffraction.