title: 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.
abstract: 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(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of 3-(tBuN=CH)C8 H5 NH (L1 ) in THF gives the dinuclear rare-earth metal alkyl complexes trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH(CH2 SiMe3 )}Ind)RE(thf)(CH2 SiMe3 )]2 (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L1 is deprotonated by the metal alkyl species and the imino C=N group is transferred to the amido group by alkyl CH2 SiMe3 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 L1 is reduced to 3-(tBuNHCH2 )C8 H5 NH (L2 ), the reaction of [Yb(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of L2 in THF, interestingly, generated the trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (major) and cis-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]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.
authors.affiliation: Laboratory of Functional 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), Fax: (+86) 553-3883517.
authors.forename: Guangchao
authors.initials: G
authors.lastname: Zhang
authors.forename: Yun
authors.initials: Y
authors.lastname: Wei
authors.forename: Liping
authors.initials: L
authors.lastname: Guo
authors.forename: Xiancui
authors.initials: X
authors.lastname: Zhu
authors.forename: Shaowu
authors.initials: S
authors.lastname: Wang
authors.forename: Shuangliu
authors.initials: S
authors.lastname: Zhou
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Mu
mesh_terms: D002070:Butadienes / Q000737:chemistry*; D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004419:Dysprosium / Q000737:chemistry; D045782:Hemiterpenes / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D008024:Ligands; D008674:Metals, Rare Earth / Q000737:chemistry*; D008968:Molecular Conformation; D010420:Pentanes / Q000737:chemistry*; D058105:Polymerization; D013237:Stereoisomerism; D015019:Yttrium / Q000737:chemistry
chemical_list: D002070:Butadienes; D056831:Coordination Complexes; D045782:Hemiterpenes; D007211:Indoles; D008024:Ligands; D008674:Metals, Rare Earth; D010420:Pentanes; C005059:isoprene; D004419:Dysprosium; D015019:Yttrium; C030374:indole
keywords: homogeneous catalysis; isoprene; ligand effects; polymerization; rare-earth metals