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 Me,AII (1), generated in situ from the reaction of Me3Al with one molar equivalent of I-2 in toluene at room temperature, afford white crystalline solids [Me2Al((S)-NH2(Ph)C(H)CH3)(2)]I-+(-) (2), [(PL)(2)Al]I-+(-) (3) or [(EL)(2)Al]I-+(-) (4), respectively. However, Me3Al reacts with one molar equivalent of PL-H producing [(Me2Al(mu-PL))(2) (5). The reaction of Me2AlI with 2,2'-ethylidene-bis-(4,6-di-tert-butylphenol) (EDBP-H-2) 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. (C) 2000 Elsevier Science S.A. All rights reserved.