Abstract

Bimetallic bis-urea functionalized salen-aluminum catalysts have been developed for cyclic carbonate synthesis from epoxides and CO2. The urea moiety provides a bimetallic scaffold through hydrogen bonding, which expedites the cyclic carbonate formation reaction under mild reaction conditions. The turnover frequency (TOF) of the bis-urea salen Al catalyst is three times higher than that of a μ-oxo-bridged catalyst, and 13 times higher than that of a monomeric salen aluminum catalyst. The bimetallic reaction pathway is suggested based on urea additive studies and kinetic studies. Additionally, the X-ray crystal structure of a bis-urea salen Ni complex supports the self-assembly of the bis-urea salen metal complex through hydrogen bonding.

Highlights

  • We report that the selfBis-urea salen ligands were synthesized in five steps following a reported procedure

  • The formation of the bis-urea salen aluminum catalyst was confirmed by high-resolution fast atom bombardment (FAB) mass aluminum spectrometry

  • The self-assembly strategy was successfully applied to the functionalized salen-aluminum catalysts for cyclic carbonate synthesis reaction from CO2 and epoxide

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Summary

Results and Discussion

We previously reported self-assembling urea-functionalized salen cobalt catalysts for the resolution of epoxides [35]. Catalyst Preparation through weak hydrogen bonding interactions [31,35]. We report that the selfBis-urea salen ligands were synthesized in five steps following a reported procedure. Assembling bimetallic strategy can be applied to the salen-aluminum catalysts for the. The ligands were prepared from commercially available 2-tert-butylphenol, and the overcyclic carbonate synthesis from CO2 and epoxides [36,37,38,39,40,41]. Metalation aluminum chloride was performed by a previously reported procedure that involved

Catalyst Preparation
X-ray Crystallography
Optimization of Cyclic Carbonates Synthesis Reaciton Conditions
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Conclusions
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