Synthesis, structure, and reactivity of yttrium complexes with chiral biaryldiamine-based N4-ligands

摘要

The chiral biaryl-based N4-ligands, (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(pyrrol-2-ylmethyleneamino)-1,1'-binaphthyl (1H2) and (S)-2,2'-bis(pyrrol-2-ylmethyIeneamino)-6,6'-dimethyl-1,1'-biphenyl (2H2), can effectively stabilize the chiral rare earth metal chloride complexes such as 1-YCl(dme) (3) and 2-YCl(dme) (4), which offers important intermediates for the preparation of chiral rare earth catalysts containing the M-C or M-X (X = heteroatom) bonds. For example, treatment of 3 with half equiv of 1Na2 in THF gives the binuclear complex 1-Y(thf)-1-Y(thf)-1 (5) in 70% yield. These complexes have been characterized by various spectroscopic techniques, elemental analyses, and X-ray diffraction analyses. The complex 5 is an active catalyst for the ring-opening polymerization of rac-lactide, affording isotactic-rich polylactides.