Electrophilic oxo (O2-) ligands multiply bonded to first-row transition metals have been implicated in reaction mechanisms of demanding oxidative biological processes, including water oxidation and C�H oxygenation. In these highly specific active sites, both primary and secondary coordination spheres of the transition metal center facilitate access to such reactive intermediates while inhibiting unproductive decomposition pathways. Synthetic first-row terminal oxo complexes are well-defined for metals as late as groups 7 and 8 (manganese and iron), and these compounds have enhanced modern understanding of their biological analogues. However, such complexes of cobalt have only been reported as non-isolable transients, although their reactivity is predicted to be valuable and the capacity to access such species through ligand design is suggested by modern electronic structure theory. Further stabilization by secondary sphere modification may allow for their isolation and subsequent spectroscopic characterization. This contribution will highlight the electronic-structure considerations of the primary sphere through ligand design and secondary sphere effects of redox-inactive cations in cobalt complexes featuring trianionic, tripodal sulfonamido ligands. The spectroscopic properties of these cobalt species, as well as their oxidation reactivity, will be described.

Primary and secondary coordination sphere effects on electronic structure, stability, and reactivity of cobalt complexes bearing trianionic tripodal ligands

248th National Meeting (2014)

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