CCC-Pincer Bis(carbene) Lanthanide Dibromides. Catalysis on Highly cis-1,4-Selective Polymerization of Isoprene and Active Species
作者：Kui Lvand Dongmei Cui
关键字：CCC-pincer; cis-1,4 selectivity; isoprene; active specie
论文来源：期刊
具体来源：具体来源：http://pubs.acs.org/doi/pdf/10.1021/om1002039
发表时间：2010年
A series of CCC-pincer 2,6-xylenyl
bis(carbene)-ligated rare-earth metal dibromides (PBNHC)LnBr2(THF) ((PBNHC) =
2,6-(2,4,6-Me3C6H2NCHCHNCCH2)2C6H3; Ln = Sc (1), Y (2), La (3), Nd (4), Sm (5),
Gd (6), Dy (7), Ho (8), Tm (9), Lu (10)) have been synthesized. Upon activation
with AlR3 (R = Me, Et, iBu) and [Ph3C]+[B(C6F5)4]?, complexes 2, 4, 6, 7, and 8
exhibited high activity and cis-1,4 selectivity (99.6%, 25 °C) toward the
polymerization of isoprene, although complexes 1, 3, 5, 9, and 10 were inert.
The selectivity was not affected by the nature of the central metal and AlR3
and was maintained at elevated temperatures up to 80 °C (97.4%). The yttrium
hydrido aluminate cation [(PBNHC)Y(μ-H)2AliBu2]+ was identified as the active
species according to NMR spectroscopic analysis.
