Lewis acid–base adducts of group 13 elements: synthesis, structure and reactivity toward benzaldehyde

Abstract

Lewis acid–base adducts [LGa-M(C₆F₅)₃] (M = B 1, Al 2, Ga 3) were prepared by the reaction of gallanediyl LGa {L = HC[C(Me)N(2,6-i-Pr₂C₆H₃)]₂} with the Lewis acids M(C₆F₅)₃ (M = B, Al, Ga). Benzaldehyde reacts with [LGa-M(C₆F₅)₃] (M = B 1, Al 2) at room temperature with the insertion and formation of [LGa(C₆F₅){CH(Ph)(OB(C₆F₅)₂)}] (4) and the zwitterionic species [LGa(C₆F₅){CH(Ph)(OAl(C₆F₅)₂)}] (5), respectively, which was found to decompose at 80 °C with the formation of {(C₆F₅)₂Al(OCH₂Ph)}₂ (6). Any attempts to isolate the insertion complex of [LGa-Ga(C₆F₅)₃] with benzaldehyde failed and only {(C₆F₅)₂Ga(OCH₂Ph)}₂ (7) was isolated at elevated temperatures. 2–5 and 7 were structurally characterized by heteronuclear NMR spectroscopy and single crystal X-ray diffraction.