A macrocyclic 'Co 0 ' complex: the relevance of ligand non-innocence to reactivity.

We present a formally zero-valent compound, [Co(Mabiq)Na(OEt2 )]2 (1). The complex was characterized by crystallographic, spectroscopic and DFT computational methods. The electronic structure is described as a CoII -(ligand-biradical). Compound 1 is reactive toward proton sources; CoI or CoII products result, depending on the source of protons used. The redox non-innocence of the Mabiq ligand, which accepts both protons and electrons, has important ramifications for reactivity.