Syntheses of chiral, intramolecularly coordinated aluminum bromides

Three aluminum compounds Ar*AlBr2 (1), Ar*AlBrtBu (2), and Ar*2AlBr (3), in corporating the chiral ligand Ar* = 2-[1(S)-Me2NCH(Me)]C6H4, have been synt hesized by salt metathesis reactions and have been characterized by multinu clear NMR (H-1, C-13 and Al-27), mass spectrometry, and elemental analysis. The molecular structure of compound 3 has been determined by a single-crys tal X-ray analysis (space group P2(1)2(1)2(1)). Alane 2 exists as temperatu re-independent equilibrium mixture of two diastereomers in solution (ratio 45:55); results of NOE experiments on 2 are discussed. Only one isomer was found for compound 3 in solution and its dynamic behavior has been investig ated by variable-temperature NMR methods; a Delta H of 56.6(4) kJ mol(-1) a nd a Delta S of -0.79(1) J K(-1)mol(-1) were deduced from band-shape analys is of the H-1-NMR signals of the N-bound methyl groups.