Deuterated N2Py2 Ligands: Building More Robust Non-Heme Iron Oxidation Catalysts

Abstract

Fe(N2Py2)/H2O2/AcOH catalytic systems provide powerful tools for efficient C–H and C═C bond oxidations (N2Py2 = bis-alkylamine-bis-pyridine ligand). Yet, the stability of these catalysts under the oxidizing conditions still remains a problem. The generally accepted catalyst decomposition pathway of Fe(N2Py2) complexes is through oxidative dimerization to form inactive oxo-bridged Fe2(μ-O)(N2Py2)2 dimers. Detailed ESI-MS analysis has now shown a catalyst decomposition pathway of ligand oxidation via C–H oxidation on the 2-pyridinylmethylene sites, followed by dissociation of the oxidized ligand from the iron center. By deuterating the 2-pyridinylmethylene sites of a series of N2Py2 ligands with variations on both alkylamine and pyridine fragments, providing access to the corresponding Fe(N2Py2-D4) complexes, longer catalysts lifetimes are achieved in catalytic oxidation reactions with all complexes. As a consequence, improved substrate conversions and product yields were consistently observed in both aliph...