RSC Publishing


Publishing

 

Cover image for Dalton Transactions, select for current issue

Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



Subscribers

Non-subscribers

Free access



Paper

Dalton Trans., 2009, 8963 - 8969, DOI: 10.1039/b910306f

Copolymerization of ethylene with norbornene catalyzed by cationic rare earth metal fluorenyl functionalized N-heterocyclic carbene complexes

Baoli Wang, Tao Tang, Yuesheng Li and Dongmei Cui

Rare earth metal bis(alkyl) complexes attached by fluorenyl modified N-heterocyclic carbene (NHC) (Flu-NHC)Ln(CH2SiMe3)2 (Flu-NHC = (C13H8CH2CH2(NCHCCHN)C6H2Me3-2,4,6); Ln = Sc ( 2a); Y ( 2b); Ho ( 2c); Lu ( 2d)), (tBuFlu-NHC)Ln(CH2SiMe3)2 (tBuFlu-NHC = 2,7-tBu2C13H6CH2CH2(NCHCCHN)C6H2Me3-2,4,6; Ln = Sc ( 1a); Lu ( 1d)) and attached by indenyl modified N-heterocyclic carbene (Ind-NHC)Ln(CH2SiMe3)2 (Ind-NHC = C9H6CH2CH2(NCHCCHN)C6H2Me3-2,4,6; Ln = Sc ( 3a); Lu ( 3d)), under the activation of AliBu3 and [Ph3C][B(C6F5)4], showed varied catalytic activities toward homo- and copolymerization of ethylene and norbornene. Among which the scandium complexes, in spite of ligand type, exhibited medium to high catalytic activity for ethylene polymerization (105 g molSc-1 h-1 atm-1), but all were almost inert to norbornene polymerization. Remarkably, higher activity was found for the copolymerization of ethylene and norbornene when using Sc based catalytic systems, which reached up to 5 × 106 g molSc-1 h-1 atm-1 with 2a. The composition of the isolated copolymer was varying from random to alternating according to the feed ratio of the two monomers (rE = 4.1, rNB = 0.013). The molecular structure of complex 1d was characterized by X-ray analysis. The influences of structural factors of complexes and polymerization conditions on both the catalytic activity and the norbornene content in the copolymer were discussed.

Graphical abstract image for this article (ID: b910306f)