An Unusual Cobalt Azide Adduct That Produces a Nitrene Species for Carbon–Hydrogen Insertion Chemistry

A family of Co­(II) complexes supported by the bulky, dianionic bis­(pyrrolyl)­pyridine pincer ligand pyrr₂py [pyrr₂py^2– = 3,5-^tBu₂-bis­(pyrrolyl)­pyridine] are reported in this work. These compounds include 1-OEt₂, 1·toluene, and 1-N₃Ad (Ad = 1-adamantyl), the latter which is prepared via addition of N₃Ad to 1-OEt₂ [1 = (pyrr₂py)­Co]. While complexes 1-OEt₂ and 1-N₃Ad are four-coordinate systems having a Co­(II) ion confined in a cis-divacant octahedral geometry, complex 1·toluene possesses a Co­(II) ion in a T-shaped environment where the toluene is interstitial and intercalated between two (pyrr₂py)Co molecules. Complex 1-N₃Ad is notable in that the organic azide binds to the metal through γ-N in a κ¹ fashion. Photolysis of 1-N₃Ad results in N₂ extrusion and formation of C–H insertion product [(pyrrpypyrrNHAd)­Co] (2). We propose complex 2 form via insertion of the nitrene (NAd) into one ^tBu C–H bond, thus resulting in a pincer ligand having a pendant secondary amine. Complexes 1-OEt₂, 1·toluene, and 1-N₃Ad and C–H insertion product 2 have been structurally characterized, and in the case of 1-OEt₂, we also present electrochemical data.