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-^<i>t</i>Bu₂-bis­(pyrrolyl)­pyridine] are reported in this work. These compounds include <b>1</b>-OEt₂, <b>1</b>·toluene, and <b>1</b>-N₃Ad (Ad = 1-adamantyl), the latter which is prepared via addition of N₃Ad to <b>1</b>-OEt₂ [<b>1</b> = (pyrr₂py)­Co]. While complexes <b>1</b>-OEt₂ and <b>1</b>-N₃Ad are four-coordinate systems having a Co­(II) ion confined in a <i>cis</i>-divacant octahedral geometry, complex <b>1</b>·toluene possesses a Co­(II) ion in a T-shaped environment where the toluene is interstitial and intercalated between two (pyrr₂py)Co molecules. Complex <b>1</b>-N₃Ad is notable in that the organic azide binds to the metal through γ-N in a κ¹ fashion. Photolysis of <b>1</b>-N₃Ad results in N₂ extrusion and formation of C–H insertion product [(pyrrpypyrrNHAd)­Co] (<b>2</b>). We propose complex <b>2</b> form via insertion of the nitrene (NAd) into one ^<i>t</i>Bu C–H bond, thus resulting in a pincer ligand having a pendant secondary amine. Complexes <b>1</b>-OEt₂, <b>1</b>·toluene, and <b>1</b>-N₃Ad and C–H insertion product <b>2</b> have been structurally characterized, and in the case of <b>1</b>-OEt₂, we also present electrochemical data.