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Dinuclear Rare‐Earth Metal Alkyl Complexes Supported by Indolyl Ligands in μ‐η 2 :η 1 :η 1 Hapticities and their High Catalytic Activity for Isoprene 1,4‐ cis ‐Polymerization
Author(s) -
Zhang Guangchao,
Wei Yun,
Guo Liping,
Zhu Xiancui,
Wang Shaowu,
Zhou Shuangliu,
Mu Xiaolong
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201405179
Subject(s) - alkyl , chemistry , deprotonation , isoprene , metal , medicinal chemistry , ligand (biochemistry) , catalysis , stereochemistry , yttrium , organic chemistry , copolymer , ion , biochemistry , receptor , polymer , oxide
Two series of new dinuclear rare‐earth metal alkyl complexes supported by indolyl ligands in novel μ‐η 2 :η 1 :η 1 hapticities are synthesized and characterized. Treatment of [RE(CH 2 SiMe 3 ) 3 (thf) 2 ] with 1 equivalent of 3‐( t BuNCH)C 8 H 5 NH ( L 1 ) in THF gives the dinuclear rare‐earth metal alkyl complexes trans ‐[(μ ‐ η 2 :η 1 :η 1 ‐3‐{ t BuNCH(CH 2 SiMe 3 )}Ind)RE(thf)(CH 2 SiMe 3 )] 2 (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L 1 is deprotonated by the metal alkyl species and the imino CN group is transferred to the amido group by alkyl CH 2 SiMe 3 insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ ‐ η 2 :η 1 :η 1 bonding modes, forming the dinuclear rare‐earth metal alkyl complexes. When L 1 is reduced to 3‐( t BuNHCH 2 )C 8 H 5 NH ( L 2 ), the reaction of [Yb(CH 2 SiMe 3 ) 3 (thf) 2 ] with 1 equivalent of L 2 in THF, interestingly, generated the trans ‐[(μ ‐ η 2 :η 1 :η 1 ‐3‐{ t BuNCH 2 }Ind)Yb(thf)(CH 2 SiMe 3 )] 2 (major) and cis ‐[(μ ‐ η 2 :η 1 :η 1 ‐3‐{ t BuNCH 2 }Ind)Yb(thf)(CH 2 SiMe 3 )] 2 (minor) complexes. The catalytic activities of these dinuclear rare‐earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio‐ and stereoselectivities for isoprene 1,4‐ cis ‐polymerization.