Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

High-valent cobalt chemistry supported by an oxidatively robust tris(carbene)borate ligand (#454)

Joe Scott 1 , Ya Su 1 , John Anderson 1
  1. University of Chicago, Chicago, ILLINOIS, United States

The generation and study of high-valent transition-metal oxo model complexes is a useful method to investigate the mechanisms of enzymatic C–H hydroxylation/substrate oxidation.1–3 Extensive modelling of the chemistry at cytochrome P450 active sights containing high-valent iron-oxo species has greatly informed synthetic oxidation methodologies,4–6 and has inspired the investigation of lesser known metal-oxo reactivity of the late transition metals Co, Ni, and Cu.7–9 However, studies of these and related high-valent oxo complexes have been limited by oxidative degradation — particularly rapid intramolecular activation of ligand aliphatic C–H bonds,10 a commonly encountered obstacle in the generation of model complexes of oxidizing intermediates.11–18 We hypothesized that eliminating this mode of degradation by replacing vulnerable ligand sp3 C–H bonds with sp3 C–F bonds would help to increase the lifetime of a transient oxidized intermediates, thus enabling more thorough characterization as well as improved reactivity with substrates. Here, we report the synthesis of a tris(imidazol-2-ylidene)borate ligand containing pendant 2,6-bis(trifluoromethyl)phenyl groups, and some of its corresponding cobalt(II) metallates. Preparation and oxidation of its corresponding oxygenated complexes is detailed, as is subsequent reactivity with substrates. Characterization of transient intermediates by electron paramagnetic resonance spectroscopy, UV-vis spectroscopy, and single crystal X-ray diffractometry, as well as results of its reactivity with C–H substrates, reveal how a more oxidatively robust ligand scaffold is enabling in the study of highly reactive high-valent complexes.

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