Organo-cerium(IV) species comprising metallocene-, hydrocarbyl-, carbene-, imido-, and oxo-complexes and related compounds: Emerging insights into bonding, electronic structures, and reactivity trends

Owing to its accessible redox couple and noble gas electronic configuration, cerium(IV) has increasingly been studied in molecular systems to probe fundamental questions of f-element bonding, 4f/5d covalency, and multi-configurational electronic structure. In this review, we examine recent developments in molecular Ce(IV) complexes featuring direct CeC, CeN, and CeO bonds. The synthetic strategies used to synthesize and isolate complexes with CeC, CeN, and CeO linkages, their reactivity profiles, and the structural, spectroscopic, electrochemical, and magnetic features of these species are described. The surveyed literature underscores the importance of supporting ligand design for achieving kinetic and thermodynamic stabilization of Ce(IV) systems containing reactive donor ligands. Many of the Ce(IV) systems described contribute to the growing body of evidence of 4f orbital participation in Ce^IV–ligand bonding. The results described herein are expected to serve as a foundation for further exploration of elusive bonding motifs in f-block compounds and will help guide the design of future cerium-based complexes that can inform the development of improved lanthanide separation technologies, catalysts, and materials properties.