Chemical fixation of carbon dioxide catalyzed via cobalt (III) ONO pincer ligated complexes

Abstract

Chemical insertion of carbon dioxide into epoxides under ambient conditions has become one of the most important methods for the construction of cyclic organic carbonates. Various active salen, salophen, and phenolate ligand based complexes have been reported for the synthesis of cyclic organic carbonates. Here we demonstrate a series of ONO pincer type cobalt (III) complexes as efficient catalysts for the cycloaddition of carbon dioxide to epoxides in neat conditions at atmospheric pressure with and without co-catalyst. A turnover number of up to 200,000 under atmospheric pressure is achieved. Moreover, the in situ generated complex shows high activity and the catalyst can be reused for at least 11 cycles without any decline in catalytic performance.

Synthesis, Characterization, and Catalytic Study of Amine-Bridged Bis(phenolato) Co(II) and Co(II/III)-M(I) Complexes (M = K or Na)

“…This is the first example of amino-bridged bis­(phenolato) cobalt complexes capable of catalyzing the cycloaddition reaction under ambient pressure, as reported examples required a pressure of 10–40 bar, regardless of whether they are Co­(II) or Co­(III) complexes. , Compared with Co­(II) and Co­(III) Schiff base complexes that are highly active under ambient pressure at 120 °C developed by Verpoort et al, , complexes 2 and 5 worked at a lower temperature of 65 °C.…”

Rational Design of Cobalt Complexes Based on the trans Effect of Hybrid Ligands and Evaluation of their Catalytic Activity in the Cycloaddition of Carbon Dioxide with Epoxide

“…Cobalt complexes based on different types of ligands have been reported, but most cobalt catalytic systems require a higher carbon dioxide pressure and reaction temperature (Table , entry 21–24). ,,, Verpoort and co-workers reported a type of Co­(III) complex catalyst based on an ONO pincer ligand (Table , entry 21), which can achieve a TON value of 200000. However, the author did not study the performance of the Co­(III) complex under mild conditions.…”

“…However, the use of cobalt complexes for the synthesis of cyclic carbonates remains scarce and is mostly limited to two types of cobalt complexes that contain salen ligands , and porphyrin ligands . Very recently, Verpoort and co-workers reported a type of Co­(III) complex catalyst based on an ONO pincer ligand, which can achieve a turnover number (TON) value of 200000. Therefore, the design of ligands is crucial for achieving high efficiency in cobalt-catalyzed CO 2 conversion.…”

Towards a selective synthetic route for cobalt amino acid complexes and their application in ring opening polymerization of rac-lactide

“…6 The most active and selective complexes contain metal centers of Al(III), 7 Fe(II) 8 In(III), 9,10 Zn(II) [11][12][13] and Y(III). 14 Cobalt based catalysts have been widely used in polymerization reactions and more recently as bio-inspired photocatalysts, [15][16][17][18][19][20][21][22] but they are far less investigated in ROP of cyclic esters. Only a few examples are known of cobalt complexes as catalysts in ROP of LA.…”