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

Abstract The chiral biaryl-based N 4 -ligands, ( R )-5,5′,6,6′,7,7′,8,8′-octahydro-2,2′-bis(pyrrol-2-ylmethyleneamino)-1,1′-binaphthyl ( 1 H 2 ) and ( S )-2,2′-bis(pyrrol-2-ylmethyleneamino)-6,6′-dimethyl-1,1′-biphenyl ( 2 H 2 ), 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 1 Na 2 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.