title: Rare-earth alkyl complexes supported by formamidinate ligands: synthesis, structure, and catalytic activity for isoprene polymerization.
abstract: A series of rare-earth metal monoalkyl complexes supported by N,N'-di(2,6-dialkylphenyl)formamidinate ligand (L)2RECH2SiMe3·thf [L(1) = HC(N-2,6-Me2C6H3)2, RE = Y (1), L(2) = HC(N-2,6-(i)Pr2C6H3)2, RE = Y (2), Er (3), Dy (4), Sm (5), and Nd (6)] were synthesized by alkyl elimination reaction or by salt metathesis reaction in good yields. All complexes were characterized by elemental analyses, FT-IR spectroscopy and single crystal X-ray diffraction. In combination with [Ph3C][B(C6F5)4] and alkylaluminium, these complexes displayed a good activity towards isoprene polymerization to give polyisoprenes with high molecular weight (M(n) > 10(4)) and narrow molecular distribution (PDI < 2.0). The influence of alkylaluminium, central metal, temperature, sequence of addition of alkylaluminium and [Ph3C][B(C6F5)4] on the polymerization of isoprene was studied. It was interesting to find that addition of the cocatalysts sequence has a great influence on the regioselectivity of the polymerization. High 1,4-regioselectivity polymerizations of isoprene (as high as 98%) were observed when the catalysts were added in the order [RE]/[alkylaluminum]/[borate].
authors.affiliation: Laboratory of Functionalized Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, P. R. China. swwang@mail.ahnu.edu.cn slzhou@mail.ahnu.edu.cn.
authors.forename: Liping
authors.initials: L
authors.lastname: Guo
authors.forename: Xiancui
authors.initials: X
authors.lastname: Zhu
authors.forename: Shuangliu
authors.initials: S
authors.lastname: Zhou
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Mu
authors.forename: Yun
authors.initials: Y
authors.lastname: Wei
authors.forename: Shaowu
authors.initials: S
authors.lastname: Wang
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Feng
authors.forename: Guangchao
authors.initials: G
authors.lastname: Zhang
authors.forename: Baojia
authors.initials: B
authors.lastname: Deng