Di- and Tri-Zinc Catalysts for the Low-Pressure Copolymerization of CO2 and Cyclohexene Oxide
摘要:
The syntheses and characterization of three new macrocyclic proligands, with variation of the para aryl ring substituent, are reported. Dizinc and trizinc acetate complexes are prepared using these ligands and are characterized using infrared and nuclear magnetic resonance spectroscopies, mass spectrometry, elemental analysis, and, for the three trizinc complexes, single-crystal X-ray diffraction. The X-ray crystallographic and spectroscopic data indicate bridging and terminal acetate coordination modes, both in the solid state and in solution, for the trizinc complexes. All of the complexes show good turnover numbers and frequencies, under 1 atm of pressure of carbon dioxide, for the copolymerization of CO2 and cyclohexene oxide to produce poly(cyclohexene carbonate), The electronic nature of the ancillary ligands' substituents influences the catalytic activity of the complex, with the electron-donating substituent reducing the activity. The dizinc catalysts show markedly higher activities than the trizinc analogues, suggesting that the coordination environment within the macrocycle is crucial to controlling the catalytic activity.
The present invention provides novel catalysts of formula (I), where M
1
and M
2
are different and are independently selected from Mg, Zn, Fe, Co, Al and Cr, and catalyst systems comprising these catalysts. The invention also relates to the use of the inventive catalysts and catalyst systems to catalyse the reaction between i) carbon dioxide and an epoxide, ii) an epoxide and an anhydride, or iii) a lactide and/or a lactone. The invention also relates to a method for producing a catalyst of formula (I).
Dinuclear metal catalysts: improved performance of heterodinuclear mixed catalysts for CO<sub>2</sub>–epoxide copolymerization
作者:P. K. Saini、C. Romain、C. K. Williams
DOI:10.1039/c3cc49158g
日期:——
A catalyst system comprising homo- and heteronuclear Zn–Mg complexes shows excellent polymerization control and exhibits higher activity than the homodinuclear catalysts for CO2–epoxide copolymerization.