Mechanistic insight into C-H bond oxidations catalyzed by an imine-based nonheme iron complex

Nonheme iron complexes are emerging as effective catalysts for reliable aliphatic C-H bond oxidation in organic synthesis.1 Catalyst’s activity and selectivity are highly affected by the nature of the ligand. Elaborated ligand structures are usually required to achieve good regioselectivities. This feature often leads to expensive and difficult to obtain complexes, thus hampering the diffusion of this synthetic methodology. In this context, we prepared a simple nonheme iron complex (3) which can be assembled directly in the reaction vessel from cheap and commercially available reagents. Complex 3 shows good activity in C-H bond oxidation, comparable to that reported for several amine-based Fe(II) complexes, albeit with a simpler structure.2 From a mechanistic point of view, complex 3 acts as a pentadentate, metal-based oxidant without involvement of free radical species, and the only oxygen source is H2O2. The first step of the catalytic cycle is the oxidation of the Fe(II) complex to Fe(III). Then, the oxidized complex looses a pyridine arm in order to make a coordination site free for H2O2 binding and activation.3 Catalytic activity of complex 3 in some hydrocarbon oxidations together with the full mechanistic investigation of complex 3 will be here reported.