Intramolecular Redox-Active Ligand-to-Substrate Single-Electron Transfer: Radical Reactivity with a Palladium(II) Complex

Coordination of the
redox-active tridentate NNO ligand LH2 to PdII yields the paramagnetic
imino­benzo­semi­quinonato
complex 3. Single-electron reduction of 3 yields diamagnetic amido­phenolato complex 4,
capable of activating aliphatic azide 5. Experimental
and computational studies suggest a redox-noninnocent pathway wherein
the redox-active ligand facilitates intramolecular ligand-to-substrate
single-electron transfer to generate an open-shell singlet “nitrene-substrate
radical, ligand radical”, enabling subsequent radical-type
C–H amination reactivity with PdII.