Syntheses of cationic four-coordinated aluminum complexes: counter-ion induced aggregation through the NH⋯I hydrogen bonds

Synthesis of cationic aluminum complexes from the reactions of Lewis bases with Me2AlI is reported. The reactions of two molar equivalents of (S)-(−)-1-phenylethylamine, (R)-(−)-pantolactone (PLH), or (S)-(−)-ethyl lactate (ELH) with Me2AlI (1), generated in situ from the reaction of Me3Al with one molar equivalent of I2 in toluene at room temperature, afford white crystalline solids [Me2Al((S)-NH2(Ph)C(H)CH3)2]+I− (2), [(PL)2Al]+I− (3) or [(EL)2Al]+I− (4), respectively. However, Me3Al reacts with one molar equivalent of PLH producing [(Me2Al(μ-PL))2 (5). The reaction of Me2AlI with 2,2′-ethylidene-bis-(4,6-di-tert-butylphenol) (EDBPH2) yields [Al(EDBP)I(Et2O)] (6) which further reacts with one molar equivalent or two molar equivalents of OPPh3 giving a neutral complex [Al(EDBP)(OPPh3)I] (7) or a cationic complex [Al(EDBP)(OPPh3)2]+I− (8). However, the cationic aluminum derivative [Al(EDBP)(HMPA)2]+I− (9) is prepared from the reaction of 6 with excess of HMPA. Crystal structures of 2, 5, and 8 determined by X-ray diffraction method are also presented.