Guanidinatoaluminum complexes: synthesis, crystal structures and reactivities

Abstract

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.