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Updated: Jun 12, 2026

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides
Published on: May 26, 2019
Synthesis of linked half sandwich rare-earth metal chlorido and borohydrido complexes and their catalytic behavior
Zhongbao Jian1, Wei Zhao, Xinli Liu
1State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin street, Changchun, 130022, China.
Abstract:
A series of rare-earth metal complexes attached by an amino-functionalized cyclopentadienyl ligand (C(5)Me(4)H-C(6)H(4)-o-NMe(2)) (1) was prepared. The metathesis reaction of the ligand lithium salt [C(5)Me(4)-C(6)H(4)-o-NMe(2)]Li with LnCl(3)(THF)(n) afforded the dichlorido complexes [(C(5)Me(4)-C(6)H(4)-o-NMe(2))(2)Ln(2)Cl(4)][LiCl(THF)(2)] (Ln = Y (2a), Lu (2b)), which are trinuclear connected by mu(3)-Cl and mu(2)-Cl multiple bridges. The straightforward metathesis reaction of Ln(BH(4))(3)(THF)(n) with equimolar [C(5)Me(4)-C(6)H(4)-o-NMe(2)]Li in THF medium yielded the first linked half sandwich ligand stabilized THF-free rare-earth metal bis(borohydrido) complexes (C(5)Me(4)-C(6)H(4)-o-NMe(2))Ln(BH(4))(2) (Ln = Sc (3a), Sm (3b)), respectively. The single component borohydrido complex 3a showed high activity towards the bulk polymerization of methyl methacrylate without specific control, which showed high iso-selectivity (mm = 80%) when the polymerization was performed in benzene medium, and switched to syndio-selectivity (rr = 74% at -20 degrees C) in polar THF medium, whilst the metal chlorido species was inert. The binary catalyst system of 3a/Mg(n)Bu(2) had similar catalytic performances when compared with 3a in THF medium, but provided enriched syndio-control in benzene solution that was in contrast to the iso-control of 3a. Surprisingly, 3a upon activation with (n)BuLi displayed an extremely high activity (1.1 x 10(6) g mol(Sc)(-1) h(-1)) and afforded syndiotactic PMMA (rr = 75%) at low polymerization temperature (-20 degrees C) in THF.
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