Alternating copolymerization of cyclohexene oxide and carbon dioxide catalyzed by noncyclopentadienyl rare‐earth metal bis(alkyl) complexes

Abstract

The syntheses of several dialkyl complexes based on rare‐earth metal were described. Three β‐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 L1Ln (CH2SiMe3)2 (Ln = Y (1a), Lu (1b), Sc (1c)), L2Ln(CH2SiMe3)2(THF) (Ln = Y (2a), Lu (2b)), and L3Lu(CH2SiMe3)2(THF) (3). All these complexes were applied to the copolymerization of cyclohexene 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 β‐diiminato yttrium bis(alkyl) complex 1a, L1Y(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 bar of CO2 atmosphere (Tp=130 °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 × 104 as well as narrow molar mass distribution (Mw/Mn = 1.7). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6810–6818, 2008

Induction of an antiinflammatory effect and prevention of cartilage damage in rat knee osteoarthritis by CF101 treatment

“…1(D)]. The decrease in inner electron binding energy of zinc was due to the coordination of Lewis basic sites with active zinc centers, indicating that the electrophilic ability of zinc was weakened 21–24. Therefore, the interaction between MgO and active centers may severely inhibited PO binding or intercalation and the rate of polymerization would be retarded, leading to lower catalytic activity than that of SiO 2 supported catalyst.…”

“…The synthesis of aliphatic polycarbonates from copolymerization of CO 2 and epoxides was pioneered by Inoue since 1969,1–5 extensive attention has been focused on the catalyst performance, and a variety of promising catalysts have been developed during the past 4 decades,6–26 including not only homogeneous catalysts like metal‐porphyrins, zinc phenolate, discrete β‐diiminate zinc, and binary or single bifunctional catalyst systems based on metal‐salen or ‐salan complexes, but also heterogeneous catalysts like ZnEt 2 ‐active hydrogen‐containing compound systems, carboxylic zinc, double metal cyanide complexes, and rare‐earth metal coordination ternary catalysts, so forth. Although the chemical or crystal structures of heterogeneous catalysts have not been completely elucidated, one of such catalysts, the rare earth ternary coordination catalyst (Y(CCl 3 COO) 3 ‐Glycerin‐ZnEt 2 ) as shown in Scheme has shown commercial potentiality producing alternate poly(propylene carbonate) (PPC, Scheme ) with high molecular weight in relatively high catalytic activity and short time 26.…”

Copolymerization of CO2 and Cyclohexene Oxide Mediated by Yb(salen)-Based Complexes

“…11 The group of Cui reported catalysts based on yttrium, lutetium and scandium catalysts with β-diimine ligands. 12 It should also be noted that lanthanide based catalysts have previously also been applied as catalysts in the formation of other types of related copolymers such as those incorporating epoxides and/or cyclic anhydrides or lactides.…”

Chemical Technologies for Exploiting and Recycling Carbon Dioxideinto the Value Chain

“…Also the terpolymerization with cyclic acid anhydrides is feasible. [157] Fundamentally, one differentiates between two distinct catalyst classes: in case of cobalt(III)-catalysts, [158][159][160][161] chromium(III)-salen and -salan complexes, [116,163] aluminum(III)-salen complexes [164] or Lewis acidic compounds [117,162] such as zinc glutarate, [165,166] zinc diiminate -ethylsulfinate [167] or rare-earth complexes [168] as catalysts, polyalkylenecarbonates with alternating repetition units are obtained; in contrast, if one uses double metal cyanide (DMC) catalysts, one acquires polyalkylenecarbonates, in which ether units occur besides the carbonate linkages. While alternating polypropylenecarbonate is on the market, the production of non-alternating polypropylenecarbonate is currently being commercialized.…”