Regeneration of nicotinamide adenine dinucleotide (NADH) has been the primary interest in the field of enzymatic transformation, especially associating oxidoreductases given the stoichiometric consumption. The synthesized carbene-ligated rhodium complex [(η 5 -Cp*)Rh(MDI)Cl] + [Cp* = pentamethylcyclopentadienyl; MDI = 1,1′-methylenebis(3,3′-dimethylimidazolium)] acts as an exceptional catalyst in the reduction of NAD + to NADH with a turnover frequency of 1730 h −1 , which is over twice that of the higher catalytic activity of the commercially available catalyst [Cp*Rh(bpy)Cl] + (bpy = 2,2'-bipyridine). Offsetting the contentious atmosphere currently taking place over the specific intermediate of the NADH regeneration, this study presents pivotal evidence of a metal hydride intermediate with a bis(carbene) ligand: a stable form of the rhodium hydride intermediate, [(η 5 -Cp*)Rh(MDI)H] + , was isolated and fully characterized. This enables thorough insight into the possible mechanism and exact intermediate structure in the NAD + reduction process.

A biomimetic system comprising a cubane-type tetranuclear complex with a [Mn 4 O 4 ] center similar to the core of the oxygen-evolving complex (OEC) of photosystem II (PSII), which is responsible for producing molecular oxygen, was synthesized from bulky carboxylate ligands and manganese by an expedient process. The synergistic effect of the exterior ligands attached to the core and the interatomic interactions led to a cubane-type morphology. This study lays the foundation for further study of metallic complexes analogous to biotic matter and contributes to structural knowledge of the second coordination sphere. In addition, the findings may shed light on the mechanism of oxygen evolution during photosynthesis.