The chemistry of the cobalt corrinoids - Recent advances and emerging themes. Part 1: The chemistry and industrial production of cobalt corrinoids.

This is the first part of a three-part review of advances in cobalt corrinoid (B12) research published between 2020 and 2025, focusing on the chemistry and industrial production of cobalt corrinoids. Although vitamin B12 is widely recognised for its biological and clinical importance, its derivatives also constitute a distinctive class of organometallic compounds whose behaviour emerges from the interplay between cobalt redox chemistry, corrin macrocycle structure, and axial ligation. Recent work increasingly treats corrinoids not as structurally conserved cofactors with narrowly defined functions, but as chemically adaptable, context-dependent systems whose properties are strongly shaped by molecular environment and speciation. Advances in analytical chemistry, particularly speciation-resolved methodologies, have clarified the functional significance of corrinoid diversity while exposing the limitations of bulk analytical approaches. Parallel developments in inorganic, structural, physical, and photochemical studies have refined understanding of how coordination environment governs electronic structure, reactivity, excited-state behaviour, and CoC bond homolysis. At the same time, synthetic chemistry, catalysis, and materials science have expanded corrinoid function into other fields, enabling applications in electrocatalysis, hybrid materials, and responsive systems. Studies of industrial production further illustrate the importance of chemical control over cofactor maturation, ligand assembly, and redox balance. These developments establish a chemical framework in which corrinoid behaviour is best understood as emergent from speciation, structure, and environment, providing the foundation for subsequent analyses of B12 biochemistry and microbiology (Part 2) and B12 and health (Part 3).