Carboxylate Shift Dynamics in Biomimetic Co(μ-OH) Complexes.

Carboxylate shift mechanisms provide low-energy pathways to accommodate changes in oxidation state and coordination number required during catalysis in metalloenzyme active sites. These processes are challenging to observe in their native enzymes and molecular models can provide insight into their mechanistic details. We report here the direct observation of a carboxylate shift reaction in biomimetic yet structurally stable dicobalt complexes featuring both monodentate and bridging acetate ligands, as well as intramolecular hydrogen-bonding interactions.

Intramolecular Hydrogen-Bond Interactions Tune Reactivity in Biomimetic Bis(μ-hydroxo)dicobalt Complexes.

Active site hydrogen-bond (H-bond) networks represent a key component by which metalloenzymes control the formation and deployment of high-valent transition metal-oxo intermediates. We report a series of dinuclear cobalt complexes that serve as structural models for the nonheme diiron enzyme family and feature a Co(μ-OH) diamond core stabilized by intramolecular H-bond interactions. We define the conditions required for the kinetically controlled synthesis of these complexes: [Co(μ-OH)(μ-OAc)(κ-OAc)(py)][PF] (), where OAc = acetate and py = pyridine with -substituent R, and we describe a homologous series of in which the -R substituent on pyridine is modulated.