Hemilabile N‐heterocyclic carbene and nitrogen ligands on Fe (II) catalyst for utilization of CO₂ into cyclic carbonate

Abstract

Six Fe (II) complexes were synthesized based on the concept of the hemilability of hybrid ligands, and their catalytic behaviors and performances were evaluated for the fixation of CO2 via the cycloaddition of epoxides. The catalytic potential of the Fe (II) complexes, in combination with bis(triphenylphosphoranylidene)ammonium chloride, have been proved to achieve the efficient conversion in some challenging substrates such as internal, disubstituted epoxides, oxetanes, and fatty acid‐derived epoxides for synthesis of cyclic carbonates under the mild reaction conditions. Ultraviolet–visible and in situ Fourier transform infrared spectroscopy experiments as well as our previous coordination of Ni complexes studies revealed that the origin of activity of Fe (II) complexes might be attributed to the trans effect between N‐heterocyclic carbene ligands and pyridine nitrogen donors.

The Use of Sustainable Transition Metals for the Cycloaddition of Epoxides and CO2 under Mild Reaction Conditions

“…[26] The use of tetranuclear alkyl aluminium complexes and (Bu) 4 NI resulted in excellent conversions at 70 °C and 1 bar of CO 2 for 24 h. [27] Moreover, Fe II coordinated to a bidentate pyridine bridged carbene ligand in the presence of (Bu) 4 NI showed high catalytic activity for the titled reaction under mild conditions. [28] Zinc is considered a perfect choice for CO 2 /epoxide coupling due to its abundance, environmentally friendly nature and the adjustable catalytic performance by modifying its coordination environment [29][30][31][32][33][34][35] using different ligands such as arylhydrazoneß-diketones, [36] bispyridylpyrrole, [37] β-diketonate, [38] N,N-dibenzyl-N,N-dimethylammonium bromide, [39] binaphthyl-bipyridyl, [40] and methylene substituted tris(2-aminoethyl)amine. [41] The performance characteristics of the above-mentioned catalytic system and the use of a co-catalyst will be discussed in detail (vide infra).…”

Chemoselective cycloadditions to epoxide derivatives of erucic acid with CO2and CS2: controlled access to value-added bio-derived compounds

“…Once the terminal epoxide containing derivatives of erucic acid had been selectively converted, we turned our attention to the conversion of the more challenging internal epoxide (Scheme 4). In this case it was necessary to optimise the binary catalyst system for selective conversion for two important reasons; (i) conversion of internal epoxides can result in cis / trans isomers depending on the reaction conditions/catalyst employed 8,14 and (ii) during the synthesis of cyclic carbonates from internal epoxides of fatty acids several reports have noted the propensity for the formation of a ketone by-product as a result of a Lewis acid promoted Meinwald rearrangement. 8 a,b , g , j ,15 In order to optimise this reaction with our gallium-based binary catalyst system, the methyl ester of erucic acid, compound 5 , was selected as a model substrate (Scheme 4(a) and Table 1).…”

“…Cyclic carbonates can be readily obtained from the atom efficient reaction of an epoxide with carbon dioxide (CO 2 ), a reaction which is commonly promoted by a Lewis acid catalyst (Scheme 1(b)), providing an attractive approach for their synthesis. 7 In this context, and unsurprisingly, with significant attention turning towards the circular economy and the application of bio-derived feedstocks, cyclic carbonates based on the methyl ester of erucic acid 8 and other fatty acids 9 have already been reported (Scheme 1(c)), with the latter recently finding interesting applications. 10 However, in general, application of these products is restricted because they only contain one reactive functional group.…”

Cycloaddition of di-substituted epoxides and CO2under ambient conditions catalysed by rare-earth poly(phenolate) complexes

“…A large number of catalysts have been developed to catalyse the cycloaddition reaction, including transition metals (e.g., Cr, [15][16][17] Fe, [18][19][20][21] Co, [22][23][24][25][26][27] and Zn [28][29][30][31][32][33] ), main group metals (e.g., Mg, [34][35][36] Al, [37][38][39][40][41][42] Ca [43][44][45][46] ), rare-earth metal catalysts [47][48][49][50][51][52][53][54][55][56][57] and organocatalysts. 5,[58][59][60][61][62][63]…”

“…A large number of catalysts have been developed to catalyse the cycloaddition reaction, including transition metals ( e.g. , Cr, 15–17 Fe, 18–21 Co, 22–27 and Zn 28–33 ), main group metals ( e.g. , Mg, 34–36 Al, 37–42 Ca 43–46 ), rare-earth metal catalysts 47–57 and organocatalysts.…”