Catalytic Mechanisms in Metal Complex Chemistry

Metal complexes serve as versatile catalysts by orchestrating bond-making and bond-breaking events through well-defined mechanistic pathways. Central steps often involve oxidative addition, wherein a metal centre inserts into a substrate bond to increase its oxidation state, and the reciprocal reductive elimination, which forms new bonds and regenerates the active catalyst. Migratory insertion events couple unsaturated substrates to metal–ligand frameworks, while outer-sphere electron transfers enable single-electron processes in photoredox and electrochemical catalysis. Ligand design—ranging from chelating phosphines to rigid pincer frameworks—modulates electronic properties, steric environment and redox potential, allowing fine-tuning of activity, selectivity and stability. Cooperative interactions in mixed-metal or mixed-valence assemblies unlock multi-electron transformations, with synergy between metal centres facilitating challenging redox or bond-activation steps. These mechanistic insights underpin advances in sustainable chemical synthesis, renewable-fuel production, small-molecule activation (for example, N₂ reduction or CO₂ fixation) and the manufacture of fine chemicals, reflecting the global significance of metal-complex catalysis in addressing energy and environmental challenges.

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Catalytic Mechanisms in Metal Complex Chemistry publication trend

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Technical terms

Oxidative addition: Metal insertion into a substrate bond, increasing the metal’s oxidation state by two units.

Reductive elimination: Coupling of two ligands on a metal centre to form a new bond, lowering the metal’s oxidation state.

Migratory insertion: Transfer of a ligand (often alkene or alkyne) into a metal–ligand bond, facilitating C–C or C–X bond formation.

Cyclotrimerisation: Metal-catalysed [2+2+2] coupling of three unsaturated molecules to form six-membered rings.

Mixed-valent complex: A coordination compound containing the same metal in different oxidation states, enabling internal electron transfer.

References

1. In Situ Routes to Catalytically Active Ru(0) Species by Reduction of Readily Available, Air-Stable Precursors. Organometallics (2018).
2. Cyclometallated Ir(III), Rh(III) and Ru(II) complexes as catalysts for the cyclotrimerisation of 1,6-diynes with monoynes. Arkivoc (2006).
3. Mixed-Metal Complexes of Mixed-Valent Dinuclear Ruthenium(II,III) Carboxylate and Tetracyanidonickelate(II). Chemistry Journal of Moldova (2014).