Isolation and Crystallographic Characterization of an Octavalent CoO Diamond Core.

High-valent cobalt oxides play a pivotal role in alternative energy technology as catalysts for water splitting and as cathodes in lithium-ion batteries. Despite this importance, the properties governing the stability of high-valent cobalt oxides and specifically possible oxygen evolution pathways are not clear. One root of this limited understanding is the scarcity of high-valent Co(IV)-containing model complexes; there are no reports of stable, well-defined complexes with multiple Co(IV) centers. Here, an oxidatively robust fluorinated ligand scaffold enables the isolation and crystallographic characterization of a Co(IV)-bis-μ-oxo complex. This complex is remarkably stable, in stark contrast with previously reported Co(IV) species that are highly reactive, which demonstrates that oxy-Co(IV) species are not necessarily unstable with respect to oxygen evolution. This example underscores a new design strategy for highly oxidizing transition-metal fragments and provides detailed data on a previously inaccessible chemical unit of relevance to O-O bond formation and oxygen evolution.