Proton-Coupled Electron Transfer from Phosphorus: A P−H/P−D Kinetic Isotope Effect of 178

Remote from the metal: The first example of proton-coupled electron transfer involving a phosphorus atom that is not directly bonded to a metal center (shown schematically; Q=benzoquinone) occurs with an osmium–phosphoraniminato complex. The large magnitude of the kinetic isotope effect is remarkable and opens the possibility of observing giant isotope effects in related reactions where proton-coupled electron transfer is the dominant mechanism.