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.

Redox chemistry and H-atom abstraction reactivity of a terminal zirconium(iv) oxo compound mediated by an appended cobalt(i) center.

The reactivity of the terminal zirconium(iv) oxo complex, O[triple bond, length as m-dash]Zr(MesNPPr)CoCN Bu (), is explored, revealing unique redox activity imparted by the pendent redox active cobalt(i) center. Oxo complex can be chemically reduced using Na/Hg or PhC to afford the Zr/Co complexes [(μ-Na)OZr(MesNPPr)CoCN Bu] () and PhCOZr(MesNPPr)CoCN Bu (), respectively. Based on the cyclic voltammogram of , Ph˙ should not be sufficiently reducing to achieve the chemical reduction of , but sufficient driving force for the reaction is provided by the nucleophilicity of the terminal oxo fragment and its affinity to bind PhC.