Carboxylate Shift Dynamics in Biomimetic Co2(μ-OH)2 Complexes.
Alyssa A DeLucia1, Lisa Olshansky1
1Department of Chemistry, Center for Biophysics and Quantitative Biology, Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3028, United States.
Inorganic Chemistry
|January 3, 2024
Summary
This study directly observed carboxylate shift reactions in biomimetic dicobalt complexes. These molecular models reveal low-energy pathways for catalytic processes in metalloenzymes.
Area of Science:
- Coordination Chemistry
- Organometallic Chemistry
- Biomimetic Catalysis
Background:
- Carboxylate shift mechanisms are crucial for metalloenzyme catalysis, enabling changes in oxidation state and coordination.
- Observing these dynamic processes in native enzymes is challenging.
- Molecular models offer valuable insights into the mechanistic details of carboxylate shifts.
Purpose of the Study:
- To directly observe and characterize carboxylate shift reactions in structurally stable biomimetic dicobalt complexes.
- To elucidate the mechanistic details of carboxylate shifts using model systems.
- To investigate the influence of ligand substituents on reaction kinetics.
Main Methods:
- Synthesis and isolation of dicobalt complexes with acetate ligands.
- Characterization using isotopic labeling, Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction.
- In situ kinetic studies using 1H-NMR spectroscopy and global fit analysis.
Main Results:
- Direct observation of a carboxylate shift triggered by Lewis acid, converting monodentate to bridging acetate ligands.
- Identification of reaction intermediates and products, including solvent adducts.
- Kinetic analysis revealed that reaction rates increase with electron-donating substituents on the pyridine ligands.
Conclusions:
- The study provides direct mechanistic insights into carboxylate shift reactivity in a biomimetic system.
- Ligand dynamicity plays a key role in mediating the transient formation of unstable metal complexes.
- Robust diamagnetic Co(III) complexes serve as effective models for studying complex catalytic mechanisms.
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