Monomeric organoaluminium complexes RAl(OR*)2 and R2AlOR* with an optically active amino alkoxide ligand

The reactions of trialkylaluminium, R3Al, with (S)-(−)α,α-diphenyl-2-pyrrolidinyl-methanol have been investigated, in which unusual bis-complexes RAl(OR*)2 were obtained [OR*=(S)-α,α-diphenyl-2-pyrrolidinyl-methoxide (Dpm), R=Me (1), Et (2), 1-Nor (3)]. A similar reaction carried out with R=t-Bu yields, by contrast, the expected mono-alkoxide R2AlOR* (4). All compounds were characterised by X-ray crystallography and NMR spectroscopy. The molecular structures are monomeric. In 1–3, the aluminium centres bonded to the nitrogen atoms of two chelating ligands are five-coordinate, while the metal atom contained in 4 is tetrahedrally surrounded. The absolute structures of all complexes were determined from X-ray diffraction data. The formation of the dative AlN bonds is stereospecific in all cases.