C–H Oxidation by H₂O₂ and O₂ Catalyzed by a Non-Heme Iron Complex with a Sterically Encumbered Tetradentate N‑Donor Ligand

The compound N,N′-dineopentyl-N,N′-bis­(2-pyridylmethyl)-1,2-ethanediamine (dnbpn) and its ferrous complex [Fe­(dnbpn)­(OTf)₂] were synthesized. The Fe­(II) complex was used to catalyze the oxidation of hydrocarbons by H₂O₂ and O₂. Although the catalyzed alkane oxidation by H₂O₂ displays a higher preference for secondary over tertiary carbons than those associated with most previously reported nonheme iron catalysts, the catalytic activity is markedly inferior. In addition to directing the catalyzed oxidation toward the less sterically congested C–H bonds of the substrates, the neopentyl groups destabilize the metal-based oxidants generated from H₂O₂ and the Fe­(II) complex. The presence of benzylic substrates with weak C–H bonds stabilizes an intermediate which we have tentatively assigned as a high-spin ferric hydroperoxide species. The oxidant generated from O₂ reacts with allylic and benzylic C–H bonds in the absence of a sacrificial reductant; less substrate dehydrogenation is observed than with related previously described systems that use O₂ as a terminal oxidant.