C-H Bond Oxidation Catalysed by Nonheme Imine-based Fe(II) Complexes

Nonheme iron complexes are emerging as promising tools in the field of C-H bond activation, as they catalyze selective hydroxylation of non-activated C-H bonds using environmentally benign hydrogen peroxide as the terminal oxidant under mild conditions. During the last decade several ligands and the corresponding iron complexes have been prepared and tested as catalysts.1 It was shown that ligand properties are crucial for catalytic activity and reaction selectivity. The more sterically encumbered is the ligand, the more selective is the catalyst. However, this feature often leads to expensive and highly elaborated ligand structures, thus hampering the diffusion of this synthetic methodology.2 In this context, we prepared a simple nonheme iron complex (3) assembled directly in the reaction vessel from cheap and commercially available reagents (2-picolylamine 1, 2-picolinaldehyde 2 and an iron salt). Complex 3 is formed immediately and quantitatively in CH3CN solution and shows good activity in aliphatic C-H bond oxidation, comparable to those reported in literature for other Fe(II) complexes, albeit with a simpler structure and at low catalyst loading.3 The results of some hydrocarbon oxidations together with the full characterization of complex 3 will be presented. Some preliminary studies on the catalytic activity displayed by other imine-based nonheme iron complexes will be also disclosed. (1) L. Que, Jr., W. B. Tolman, Nature 2008, 455, 333-340. (2) Gòmez L., Garcia-Bosch I., Company A., Benet-Bucholz J., Polo A., Sala X., Ribas X., Costas M.; Angew. Chem. Int. Ed. 2009, 48, 5720-5723; Gorminsky P. E., White M. C.; J. Am. Chem. Soc. 2013, 135, 14052-14055; Cantà, M., Font D., Gòmez L., Ribas X., Costas M.; Adv. Synth. Cat. 2014, 356, 818-830. (3) Olivo G., Arancio G., Mandolini L., Lanzalunga O., Di Stefano S., submitted