Rare-Earth-Metal Mixed Hydride/Aryloxide Complexes Bearing Mono(cyclopentadienyl) Ligands. Synthesis, CO2 Fixation, and Catalysis on Copolymerization of CO2 with Cyclohexene Oxide
writer：Dongmei Cui, Masayoshi Nishiura, Olivier Tardif and Zhaomin Hou
keywords：hydrogenolysis; trans-accommodated; hydride bridges; aryloxide; metal centers
source：期刊
specific source：http://pubs.acs.org/doi/pdf/10.1021/om800170x
Issue time：2008年
Hydrogenolysis
of mono(cyclopentadienyl)-ligated rare-earth-metal bis(alkyl) complexes
Cp′Ln(CH2SiMe3)2(THF) (Ln = Y (1a), Dy
(1b), Lu (1c); Cp′ = C5Me4SiMe3)
with PhSiH3 afforded the mixed hydride/alkyl complexes
[Cp′Ln(μ-H)(CH2SiMe3)(THF)]2 (Ln = Y (2a),
Dy (2b), Lu (2c)). The overall structure of complexes 2a?c is
a C2-symmetric dimer containing a planar symmetric Ln2H2 core
at the center of the molecule. Deprotonation of ArOH (Ar = C6H2-tBu2-2,6-Me-4)
by the metal alkyl group of 2a?c led to formation of
the mixed hydride/aryloxide derivatives [Cp′Ln(μ-H)(OAr)]2 (Ln
= Y (3a), Dy (3b), Lu (3c)), which adopt the dimeric
structure through hydride bridges with trans-accommodated terminal
aryloxide groups. Complexes 3a?c swiftly reacted with
CO2 to generate the mixed formate/carbonate complexes
[Cp′Ln(μ-η1:η1-O2CH)(μ-η1:η1-O2COAr)]2 (Ln
= Y (4a), Dy (4b), Lu (4c)). The two Cp′Ln fragments in
these complexes are bridged by the formate and carbonate species, respectively,
to form two square-pyramidal geometries around the metal centers. Furthermore,
complexes 3a?c initiated the copolymerization of CO2 and
cyclohexene oxide (CHO) under mild conditions to afford polymers with modest
molecular weights and high carbonate linkages (92?99%).
