Syntheses of cationic four-coordinated aluminum complexes: counter-ion induced aggregation through the N-H center dot center dot center dot 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 (E L-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 cryst alline 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 m olar equivalent of PL-H producing [(Me2Al(mu-PL))(2) (5). The reaction of M e2AlI 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 cationi c aluminum derivative [Al(EDBP)(HMPA)(2)]I-+(-) (9) is prepared from the re action of 6 with excess of HMPA. Crystal structures of 2, 5, and 8 determin ed by X-ray diffraction method are also presented. (C) 2000 Elsevier Scienc e S.A. All rights reserved.