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

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 degrees C with the formation of {(C6F5)(2)Al(OCH2Ph)}(2) (6). Any attempts to isolate the insertion complex of [LGa-Ga(C6F5)(3)] with benzaldehyde failed and only {(C6F5)(2)Ga(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.