Characterization of a Reactive Rh2 Nitrenoid by Crystalline Matrix Isolation

The fleeting lifetimes of reactive intermediates in C–H functionalization chemistry often prevent their direct characterization. For example, the critical nitrenoid intermediates that mediate Rh2-catalyzed C–H amination have eluded characterization for more than 40 years. In the absence of structural characterization of these species, methodological development is often computationally guided. Here we report the first X-ray crystal structure of a reactive Rh2 nitrenoid, enabled by N2 elimination from an organic azide ligand within a single-crystal matrix. The resulting high-resolution structure displays metrical parameters consistent with a triplet nitrene complex of Rh2. The demonstration of facile access to reactive metal nitrenoids within a crystalline matrix provides a platform for structural characterization of the transient species at the heart of C–H functionalization.