Catching a copper nitrene Nitrogen typically forms three bonds in its stable compounds. If only one bond is available, the resultant electron-deficient nitrene can react rapidly with hydrocarbons to fill out its valence shell. Metal-stabilized nitrenes have been widely implicated in carbon-nitrogen bond-forming reactions, but the putative intermediates have rarely been synthesized directly. Carsch et al. now report preparation of a copper nitrene complex from an azide precursor. X-ray absorption and diffraction studies support a triplet electronic state that does not engage in multiple bonding with the copper center. Science , this issue p. 1138