Guanidinatoaluminum complexes: synthesis, crystal structures and reactivities

Treatment of diethylaminolithium with carbodiimide (CyNCNCy or CyNCNC6H5) and dimethylaluminium chloride (AlMe2Cl) in a molar ratio of 1 : 1 : 1 afforded two kinds of guanidinatoaluminum complexes, [{(Et2N)C(NR1)(NR2)}AlMe2] (R1, R2 = Cy (1); R1 = Cy, R2 = C6H5 (2)) and [{(Et2N)C(NCy)(NC6H5)}2AlMe] (3). The reactivities of the mononuclear guanidinatoaluminum complexes (1 and 2) with O2 or carbodiimide were studied. The complexes of [{(Et2N)C(NCy)2}AlMe(μ-OMe)]2 (4) and [{N(C6H5)C(NCy)N(C6H5)C(NEt2)N(Cy)}AlMe2] (5) were produced by introducing dry oxygen or carbodiimide (CyNCNC6H5) slowly into the solution of the mononuclear guanidinatoaluminum complex (1 or 2). Meanwhile, the addition of O2 or carbodiimide (ArNCNC6H5, Ar = 2,6-Me2C6H3) to the reaction solution of diethylaminolithium with ArNCNC6H5 and AlMe2Cl in a molar ratio of 1 : 1 : 1 yielded [(Et2N)C(NC6H5)(NAr)AlMe(μ-OMe)]2 (6) and [{N(C6H5)C(NAr)N(C6H5)C(NEt2)N(Ar)}AlMe2] (7). In addition, a one-pot reaction of diethylaminolithium with CyNCNCy and AlMe2Cl in a molar ratio of 1 : 1 : 1 in the presence of H2O produced a tetranuclear guanidinatoaluminum complex, (8), which was also prepared by treatment of complex 1 with equivalent AlMe3 and H2O in 35% yield. All complexes 1–8 were characterized by 1H, 13C NMR spectroscopy and single crystal X-ray diffraction analysis.