Highly Active Carbene Potassium Complexes for the Ring-Opening Polymerization of ε-Caprolactone

Bhunia, Mrinal ; Vijaykumar, Gonela ; Adhikari, Debashis ; Mandal, Swadhin K. (2017) Highly Active Carbene Potassium Complexes for the Ring-Opening Polymerization of ε-Caprolactone Inorganic Chemistry, 56 (23). pp. 14459-14466. ISSN 0020-1669

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Official URL: http://doi.org/10.1021/acs.inorgchem.7b01892

Related URL: http://dx.doi.org/10.1021/acs.inorgchem.7b01892

Abstract

Herein we report the synthesis of two complexes of potassium employing strongly nucleophilic carbenes, such as cyclic “(alkyl)(amino)carbene (cAAC) and abnormal N-heterocyclic carbene (aNHC). Both complexes are dimeric in the solid state and the two potassium centers are bridged by trimethylsilylamide. In these complexes, the carbene- - -K interaction is predominantly electrostatic in character, which has been probed thoroughly by NBO and AIM analyses. Indeed, the delocalization energy of the cAAC lone pair calculated from the second-order perturbation theory was only 5.21 kcal mol–1, supporting a very weak interaction. The solution-state behavior of these molecules, as inferred from NOESY spectra, hints that the weak carbene- - -K interaction is retained in nonpolar solvents, and the bond is not dissociated at least on the NMR time scale. We took advantage of such a weak interaction to develop highly effective ring-opening polymerization catalysts for ε-caprolactone and rac-lactide. The efficacy of these catalysts is prominent from a very high substrate/metal-initiator ratio as well as very low dispersity index of the obtained polymer chains, reflecting significant control over polymerization.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:118289
Deposited On:19 May 2021 18:45
Last Modified:19 May 2021 18:45

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