Highly Selective Single‐Component Formazanate Ferrate(II) Catalysts for the Conversion of CO₂ into Cyclic Carbonates

Abstract

The development of new families of active and selective single‐component catalysts based on earth‐abundant metal is of interest from a sustainable chemistry perspective. In this context, anionic mono(formazanate) iron(II) complexes bearing labile halide ligands, which possess both Lewis acidic and nucleophilic functionalities, have been developed as novel single‐component homogeneous catalysts for the reaction of CO2 with epoxides to produce cyclic carbonates. The influence of the halide ligand and the electronic properties of the formazanate ligand backbone on the catalytic activity are investigated by employing the iron(II) complexes with and without an additional nucleophile. Very high selectivity is achieved towards the formation of the cyclic carbonate products from various terminal and internal epoxides without the need of a cocatalyst.

The Role of Water Revisited and Enhanced: A Sustainable Catalytic System for the Conversion of CO2 into Cyclic Carbonates under Mild Conditions

“…[5,48] Indeed, even upon using ah igher catalyst loading (3 mol %B u 4 NI), a very low cyclohexane carbonate yield was obtainedi nt he absence of water (Table 2, entry 13). [5,48] Indeed, even upon using ah igher catalyst loading (3 mol %B u 4 NI), a very low cyclohexane carbonate yield was obtainedi nt he absence of water (Table 2, entry 13).…”

“…The substrate scope of the catalytic system consistingo f Bu 4 NI and water was extended by investigating the conversion of an internal epoxide,c yclohexene oxide.T he steric hindrance aroundt he epoxideg roup and the geometrics train in the cyclic carbonate caused by the two adjacent rings make the conversion of cyclohexene oxide to cyclohexane carbonate more challenging than that of terminal epoxides. [5,48] Indeed, even upon using ah igher catalyst loading (3 mol %B u 4 NI), a very low cyclohexane carbonate yield was obtainedi nt he absence of water ( Table 2, entry 13). The addition of water as HBD proved very beneficial in this case as well, leadingt oa more than four-fold increasei na ctivity,a lthough the achieved cyclic carbonate yield is still moderate under the employed conditions ( Table 2, .…”

Formazanate coordination compounds: synthesis, reactivity, and applications

“…It was proposed that the lability of a halide ligand in 25 allows binding of epoxide to the Lewis acidic Fe center, and the halide that is liberated acts as a nucleophile for the ring-opening of the epoxide to initiate the reaction. 34 Formazanate complexes with the heavier elements in group 8 (Ru, Os) have only been sporadically investigated. Early work by Ibers and co-workers described the synthesis of complexes in which C-H activation of the NPh group took place to afford cyclometallated derivatives.…”

“…Scheme 9 (a) Synthesis of ferrate complexes 25 and subsequent halide exchange for isocyanide to give cationic complex 26. (b) Application of 25 in the catalytic conversion of CO 2 /epoxide to cyclic carbonates 33,34.…”

Niobium oxide prepared through a novel supercritical-CO2-assisted method as a highly active heterogeneous catalyst for the synthesis of azoxybenzene from aniline

“…Nb 2 O 5 was prepared using a scCO 2 -assisted precipitation method, with a novel protocol developed by adapting the synthesis methods of other metal oxides in scCO 2 medium 36,38,39 and by applying it to a precipitation method inspired by those used in the literature to prepare Nb 2 O 5 . [40][41][42] The synthesis was carried out in a high-throughput scCO 2 reactor unit manufactured by Integrated Lab Solutions (ILS), 43 which consists of two modules: a batch reactor equipped with a borosilicate glass window to allow visualisation of the phase behaviour within the reactor, and a block with 10 batch reactors ( Fig. S1 †).…”