Dinuclear aluminum complexes supported by amino- or imino-phenolate ligands: Synthesis, structures, and ring-opening polymerization catalysis of rac-lactide

摘要

Two series of ligand precursors [2-OH-3-(CH_2NR _2)-5-MeC_6H_2]_2CH_2 (1: NR_2 = NMe_2; 2: NR_2 = N(CH_2) _4; 3: NR_2 = N(CH_2)_5; 4: NR _2 = N(Me)Ph) and [2-OH-3-(CHNR)-5-MeC_6H_2] _2CH_2 (10: R = 2,6-Pri2C_6H_3; 11: R = p-MeC_6H_4; 12: R = p-ClC_6H_4; 13: R = p-MeOC_6H_4; 14: R = Bu~t) were prepared. These compounds reacted with AlMe_3 to afford corresponding dinuclear aluminum complexes [AlMe_2{2-O-3-(CH_2NR_2)-5- MeC_6H_2}]_2CH_2 (6: NR_2 = NMe_2; 7: NR_2 = N(CH_2)_4; 8: NR _2 = N(CH_2)_5; 9: NR_2 = N(Me)Ph) and [AlMe_2{2-O-3-(CHNR)-5-MeC_6H_2}] _2CH_2 (15: R = 2,6-Pri2C_6H_3; 16: R = p-MeC_6H_4; 17: R = p-ClC_6H_4; 18: R = p-MeOC_6H_4; 19: R = Bu~t). All the compounds were characterized by ~1H and ~(13)C NMR spectroscopy and elemental analyses. Complexes 6 and 16 were additionally characterized by single crystal X-ray diffraction techniques. Catalysis of the aluminum complexes towards the ring-opening polymerization of rac-lactide was evaluated in the presence of benzyl alcohol. All the polymerization reactions proceed in a controlled manner.