Scorpionates in CO2 conversion: established applications in cyclic carbonate synthesis and emerging reactivity pathways.

Abstract

Starting with the pioneering work by Trofimenko in the 1960s, scorpionate ligands have become pivotal ligands in coordination chemistry and catalysis. Their tridentate κ3-coordination mode promotes the formation of stable metal complexes while allowing the modulation of electronic and steric properties in these entities. Moreover, their tuneable coordination behaviour supports multiple binding arrangements, expanding their potential applicability as universal ligands. This review provides a comprehensive overview of the main advances in exploring scorpionate complexes as efficient catalysts for CO2 fixation processes. Particularly, this work focuses on the preparation of 5-membered cyclic carbonates (CCs) as well as alternative emerging CO2 transformation pathways such as hydrogenation, hydroboration and N-formylation. Thus, we have adopted this approach by highlighting the most representative and efficient scorpionate catalyst systems reported to date, including scorpionate-like organocatalysts, mononuclear systems (aluminium, zinc, zirconium, rare earth, iron and nickel), multinuclear systems (di- and trinuclear aluminium-based species), and bicomponent and bifunctional systems, for the catalytic processes mentioned above. This review represents the first contribution that summarises and illustrates the current state of the art related to the use of scorpionate-based systems as efficient catalysts for the preparation of highly valued molecules through CO2 fixation processes. This account finally aims to guide future research towards potential improvements in catalyst design, as well as broader applications and new opportunities to be explored in the preparation of more sustainable value-added chemicals.