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

Abstract

Synthesis of cationic aluminum complexes from the reactions of Lewis bases with Me 2AlI is reported. The reactions of two molar equivalents of ( S)-(−)-1-phenylethylamine, ( R)-(−)-pantolactone (PLH), or ( S)-(−)-ethyl lactate (ELH) with Me 2AlI ( 1), generated in situ from the reaction of Me 3Al with one molar equivalent of I 2 in toluene at room temperature, afford white crystalline solids [Me 2Al(( S)-NH 2(Ph)C(H)CH 3) 2] +I − ( 2), [(PL) 2Al] +I − ( 3) or [(EL) 2Al] +I − ( 4), respectively. However, Me 3Al reacts with one molar equivalent of PLH producing [(Me 2Al(μ-PL)) 2 ( 5). The reaction of Me 2AlI with 2,2′-ethylidene-bis-(4,6-di- tert-butylphenol) (EDBPH 2) yields [Al(EDBP)I(Et 2O)] ( 6) which further reacts with one molar equivalent or two molar equivalents of OPPh 3 giving a neutral complex [Al(EDBP)(OPPh 3)I] ( 7) or a cationic complex [Al(EDBP)(OPPh 3) 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.