On the real catalytically active species for CO2 fixation into cyclic carbonates under near ambient conditions: Dissociation equilibrium of [BMIm][Fe(NO)2Cl2] dependant on reaction temperature

Abstract

An imidazolium based iron-containing ionic liquid [BMIm][Fe(NO)2Cl2] (BMIm = 1n-butyl-3-methyl-imidazolium) has been synthesized for the first time and fully characterized employing a wide range of techniques. The iron-based containing ionic liquid was found to be an active catalyst for the cycloaddition of CO2 to epoxides, giving high conversions for various substrates under near ambient conditions. In addition, the catalytic system showed a good recycling performance for five consecutive reaction cycles. Key mechanistic studies demonstrated that a bifunctional catalytic system is generated in situ by the partial dissociation of the iron-based ionic liquid into [BMIm][Cl], which results in a very efficient catalyst without the need of any additive or co-catalyst. The metal center plays a role as Lewis acid and activate the epoxide group, and the chloride anion, as part of [BMIm][Cl] moiety, acts as nucleophile and leads to the ring opening through a nucleophilic attack on the less sterically-hindered Che process is favoured by an interaction via H-bonding between the substrate and the H-C2 of the imidazolium ring, as was demonstrated by additional experiments. Kinetic studies indicated that the process followed first-order kinetics with respect to epoxide concentration and proved the existence of a reversible coordination/de-coordination equilibrium in which the active species are generated from the [BMIm][Fe(NO)2Cl2] complex.

The Nature of Carbon Dioxide in Bare Ionic Liquids

“…Moreover, in various cases, the interaction of the IL pair changes the reactivity of the trapped water, which can easily react with substrates, products, and even with the IL. [8,9,19,[27][28][29][30] In this contribution, the different modes of interaction of CO 2 with bare ILs containing both nonbasic and mainly basic anions will be presented and discussed critically, considering recent examples reported in the literature. Finally, it will be demonstrated that simple concepts of acid-base chemistry can be used to explain and to design new ionic fluids for CO capture and activation.…”

Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4]

“…As a result, these materials exhibit unusual anisotropic thermal expansion processes, which can be related to the ability of the organic moiety to present translational and reorientational phenomena that govern properties such as magnetism and solid-state ionic conduction. Moreover, from a technological point of view, due to their very interesting features in terms of Lewis-acidity, they are recently being applied as catalysts in reactions such as glycosidation, 18,19 Michael addition, 20 desulfurization 21 and CO 2 xation into cyclic carbonates, 22 among others.…”

[Zinc(II)(Pyridine‐Containing Ligand)] Complexes as Single‐Component Efficient Catalyst for Chemical Fixation of CO2 with Epoxides

“…Reactive epoxide such as (+ /À )-epichlorohydrin 3 b, due to electronegative effect of its substituent that facilitated the nucleophilic attack to open the epoxide ring, [27] gave quantitative yield of cyclic carbonate (entry 2, Table 3). On the other hand, the low solubility of complex 2 b in alkyl epoxides even at high temperatures caused a drop in the reaction yield, whose effect is more pronounced on increasing chain length, as exemplified by the difference between propylene oxide and 1,2-hexene oxide (compare entry 3 with entry 7 in Table 3).…”