Ion exchange resin supported tetrahalo-metallates as efficient catalysts for the synthesis of cyclic carbonates and carbamates from CO₂

Ammonium tetrahalo-metallates of the first transition series elements combine ease of preparation and storage, excellent catalytic activity and extremely low production costs.1 Recently we showed that ammonium ferrates and zincates are active catalysts in the cycloaddition of CO2 to aziridines and epoxides to yield carbamates and carbonates, respectively.2 3 4 These reactions display interesting features in terms of eco-sustainability, since the coupling occurs with 100% of atom-economy, valorizing waste CO2 to yield value-added products. Additionally, metallates can be easily anchored on anionic exchange resins, such as Amberlyst® and Amberlite® (Figure 1). A simple and efficient protocol to functionalize Amberlyst® ionic exchange resins with ferrate and zincate complexes was thus developed. The obtained materials can be finely tuned both by choosing the preferred metallic halide and resin reticular size, effectively controlling the productivity of the reaction and pave the way for a future flow implementation. We present our recent progress in this field of chemistry, highlighting both the benefits and the challenges encountered in the functionalization of ion exchange resins with tetrahalo-metallates.