Main advances in the application of scorpionate-based catalytic systems for the preparation of sustainable polymers

Abstract

Scorpionate ligands have emerged as pivotal components in the field of coordination chemistry and catalysis since the seminal work by Trofimenko in the late 1960s. These species have demonstrated an extraordinarily rich tridentate coordination chemistry, enhancing the stability of metal complexes. In addition, they offer the possibility of modifying the chemical and electronical features as κ³-ligands, providing a wide variety of potential substrates with multiple donor atoms. Furthermore, this type of ligand has shown wide versatility in its coordination mode and can adopt different binding arrangements, expanding its potential as a universal ligand. This review provides a comprehensive overview of the main advances in exploring scorpionate complexes based on the tris(1H-pyrazol-1-yl)borate and bis(1H-pyrazol-1-yl)methane moieties, which have been recently reported as efficient catalysts for the synthesis of sustainable polymers. Specifically, this work focuses on the preparation of biorenewable polylactides (PLAs), other polyesters and polycarbonates (PCs), derived from cyclohexene carbonate, polylactide-co-polycarbonate copolymers and alternative sustainable polymeric materials. Thus, we have faced this challenge by selecting and classifying the most well-performed scorpionate catalyst system, including divalent (magnesium, calcium, zinc and iron) and other metals (rare-earth metals and zirconium), for each of 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 sustainable polymer materials. This account finally aims to guide future research towards the development of more eco-friendly catalytic processes in promoting sustainable polymers to achieve relevant commodities.