Synthesis, structure, and catalytic activity of titanium complexes with new chiral 11,12-diamino-9,10-dihydro-9,10-ethanoanthracene-based ligands

摘要

A new series of organo-titanium complexes have been prepared from the reaction between Ti(NMe_2)_4 and C_2-symmetric ligands, (R,R)-11,12-bis(pyrrol-2-ylmethyleneamino)-9,10-dihydro-9,10- ethanoanthracene (1H_2), and (R,R)-bis(diphenylthiophosphoramino)-9, 10-dihydro-9,10-ethanoanthracene (2H_2), (R,R)-11,12- bis(mesitylenesulphonylamino)-9,10-dihydro-9,10-ethanoanthracene (3H _2) and (R,R)-bis(diphenylthiophosphoramino)-1,2-cyclohexane (4H _2). Treatment of Ti(NMe_2)_4 with 1 equiv of 1H_2 gives, after recrystallization from a benzene solution, the binuclear double helicate titanium amide (1)_2[Ti(NMe _2)_2]_2(5) in 71% yield. While under similar reaction conditions, reaction of Ti(NMe_2)_4 with 1 equiv of 2H_2, 3H_2 or 4H_2 gives, after recrystallization from a toluene or benzene solution, the mononuclear single helicate titanium amides (2)Ti(NMe_2)_2 (6), (3)Ti(NMe_2) _2 (7) and (4)Ti(NMe_2)_2 (8), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 5-8 have further been confirmed by X-ray diffraction analyses. The titanium amides are active catalysts for the polymerization of rac-lactide, leading to the isotactic-rich polylactides. Synopses: A new series of chiral organo-titanium complexes have been prepared. They are active catalysts for the polymerization of rac-lactide, leading to the isotactic-rich polylactides.