Well-defined molecular catalysts for the reduction of N-2 to NH3 with protons and electrons remain very rare despite decades of interest and are currently limited to systems featuring molybdenum or iron. This report details the synthesis of a molecular cobalt complex that generates superstoichiometric yields of NH3 (>200% NH3 per Co-N-2 precursor) via the direct reduction of N-2 with protons and electrons. While the NH3 yields reported herein are modest by comparison to those of previously described iron and molybdenum systems, they intimate that other metals are likely to be viable as molecular N, reduction catalysts. Additionally, a comparison of the featured tris(phosphine)borane Co-N-2 complex with structurally related Co-N-2 and Fe-N-2 species shows how remarkably sensitive the N, reduction performance of potential precatalysts is. These studies enable consideration of the structural and electronic effects that are likely relevant to N-2 conversion activity, including the pi basicity, charge state, and geometric flexibility.