Alternating Copolymerization of Cyclohexene Oxide and Carbon Dioxide Catalyzed by Noncyclopentadienyl Rare-Earth Metal Bis(alkyl) Complexes
作者：Zhichao Zhang, Xinli Liu, DongmeiCui
關(guān)鍵字：catalysts， copolymerization，cyclohexene oxide，polycarbonates，rare-earth metals
論文來源：期刊
具體來源：http://apps.webofknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=4&SID=V2hxdXl
發(fā)表時(shí)間：2008年
The
syntheses of several dialkyl complexes based on rare-earth metal were
described. Three beta-diimine compounds with varying N-aryl substituents (HL1 =
(2-CH3O(C6H4))N=C(CH3)CH=C(CH3)NH(2-CH3O(C6H4)), HL2 = (2,4,6-(CH3)(3)
(C6H2))N=C(CH3)CH=C(CH3)NH(2,4,6-(CH3)(3)(C6H2)), HL3 = PhN=C(CH3)CH(CH3) NHPh)
were treated with Ln(CH2SiMe3)(3)(THF)(2) to give dialkyl complexes L(1)Ln
(CH2SiMe3)(2) (Ln = Y (1a), Lu (1b), Sc (1c)), L(2)Ln(CH2SiMe3)(2)(THF) (Ln = Y
(2a), Lu (2b)), and (LLu)-Lu-3(CH2SiMe3)(2)(THF) (3). All these complexes were
applied to the copolymerization ofcyclohexene oxide (CHO) and
carbon dioxide as single-component catalysts. Systematic investigation revealed
that the central metal with larger radii and less steric bulkiness were
beneficial for the copolymerization of CHO and CO2. Thus,
methoxy-modified beta-diiminato yttrium bis(alkyl) complex 1a,
(LY)-Y-1(CH2SiMe3)(2), was identified as the optimal catalyst, which converted
CHO and CO2 to polycarbonate with a TOF of 47.4 h(-1) in 1,4-dioxane
under a 15 barof CO2 atmosphere (T-p = 130 degrees C), representing the
highest catalytic activity achieved by rare-earth metal catalyst. The resultant
copolymer contained high carbonate linkages (> 99%) with molar mass up to
1.9 x 10(4) as well as narrow molar mass distribution (M-w/M-n = 1.7). (c) 2008
Wiley Periodicals, Inc.