Hydrogen atom abstraction as a synthetic route to a square planar Co complex with a redox-active tetradentate PNNP ligand.

Redox-active ligands improve the reactivity of transition metal complexes by facilitating redox processes independent of the transition metal center. A tetradentate square planar (PNCHCHNP)Co (1) complex was synthesized and the ethylene backbone was dehydrogenated through hydrogen atom abstraction to afford (PNCHCHNP)Co (2), which now contains a redox-active ligand. The ligand backbone of 2 can be readily hydrogenated with H to regenerate 1.