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 Rh-2-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 Rh-2 nitrenoid, enabled by N-2 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 Rh-2. 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.