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  • Title: Lanthanide and group 4 metal complexes with new chiral biaryl-based NNO-donor ligands.
    Author: Zi G, Wang Q, Xiang L, Song H.
    Journal: Dalton Trans; 2008 Nov 21; (43):5930-44. PubMed ID: 19082049.
    Abstract:
    A new series of lanthanide and group 4 metal complexes have been prepared from the reactions between Ln[N(SiMe(3))(2)](3) or M(NMe(2))(4) and chiral ligands, (R)-2-(pyrrol-2-ylmethyleneamino)-2'-methoxy-1,1'-binaphthyl (H), (S)-5,5',6,6',7,7',8,8'-octahydro-2-(pyrrol-2-ylmethyleneamino)-2'-methoxy-1,1'-binaphthyl (H) and (R)-2-(pyrrol-2-ylmethyleneamino)-2'-methoxy-6,6'-dimethyl-1,1'-biphenyl (H). The steric effect of the ligand coupled with the size effect of the ions plays an important role in the formation of the lanthanide complexes. For example, treatment of H with 1 equiv of Ln[N(SiMe(3))(2)](3) (Ln = Y, Yb) in toluene gives the tris-ligated complexes, ()(3)Y.C(7)H(8) (.C(7)H(8)) and ()(3)Yb.2C(7)H(8) (.2C(7)H(8)) in good yields; reaction of H with 1 equiv of Sm[N(SiMe(3))(2)](3) also gives the tris-ligated product ()(3)Sm (), while treatment of H with 1 equiv of Ln[N(SiMe(3))(2)](3) (Ln = Y, Yb) leads to the isolation of the bis-ligated organolanthanide amides ()(2)LnN(SiMe(3))(2).2C(6)H(6) (Ln = Y (.2C(6)H(6)), Yb (.2C(6)H(6))) in good yields. Reaction of H, H or H with 1 equiv of M(NMe(2))(4) gives, after recrystallization from a toluene or benzene solution, the chiral bis-ligated titanium amides ()(2)Ti(NMe(2))(2).0.75C(7)H(8) (.0.75C(7)H(8)), ()(2)Ti(NMe(2))(2) (), ()(2)Ti(NMe(2))(2).C(6)H(6) (.C(6)H(6)), and zirconium amides ()(2)Zr(NMe(2))(2).C(7)H(8) (.C(7)H(8)), ()(2)Zr(NMe(2))(2) (), ()(2)Zr(NMe(2))(2).C(6)H(6) (.C(6)H(6)), in good yields, respectively. Treatment of Zr(NMe(2))(4) with 1 equiv of (R)-2-(pyrrol-2-ylmethylamino)-2'-methoxy-1,1'-binaphthyl (H(2)), which was prepared from the reduction of H with an excess of NaBH(4) in a solvent mixture of MeOH and toluene (1 : 1) at 50 degrees C, gives the trinuclear complex [(R)-2-O-C(20)H(12)-2'-(NCH(2)C(4)H(3))](2)Zr(3)(NMe(2))(6).2C(7)H(8) (.2C(7)H(8)) in 65% yield. Organolanthanide amides and zirconium amides are active catalysts for asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to good yields with moderate ee values, while the titanium amides are not. During the course of the catalytic reaction, is decomposed leading to the isolation of ()(3)Y.C(7)H(8) (.C(7)H(8)) in 35% yield from a toluene solution. The organolanthanide amides are also active catalysts for ring-opening polymerization of rac-lactide, giving isotactic-rich polylactides. All compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of compounds H, H, , and have further been confirmed by X-ray diffraction analyses.
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