In general, multielectron redox reactions are rare. Nonetheless, important examples of these processes are efficiently catalyzed by metalloenzymes such as xanthine oxidase, sulfite oxidase, nitrate reductase, and cytochrome P450. These enzymes apparently operate via an atom transfer process-the net result involves oxygen atom transfer in an overall two-electron redox reaction. 1 For most of these enzymes, there is little or no information on reaction pathways. Furthermore, it is difficult to model these enzymes because of the paucity of clearly established multielectron atom transfer processes. Development of systems that would allow studies of the rates, mechanisms, and energetics of multielectron reactions would clearly benefit our understanding of these important processes. Recently, a net three-electron transfer mediated by an unprecedented reversible nitrogen atom transfer was discovered in our laboratory. 2 As part of our continuing study of multielectron transfer, we now report that an analogous twoelectron redox process can be mediated by reversible nitrogen atom transfer.