Oxidation of ethane to ethanol by N2O in a metal–organic framework with coordinatively unsaturated iron(II) sites

Enzymatic haem and non-haem high-valent iron–oxo species are known to activate strong C–H bonds, yet duplicating this reactivity in a synthetic system remains a formidable challenge. Although instability of the terminal iron–oxo moiety is perhaps the foremost obstacle, steric and electronic factors also limit the activity of previously reported mononuclear iron( IV )–oxo compounds. In particular, although nature's non-haem iron( IV )–oxo compounds possess high-spin S = 2 ground states, this electronic configuration has proved difficult to achieve in a molecular species. These challenges may be mitigated within metal–organic frameworks that feature site-isolated iron centres in a constrained, weak-field ligand environment. Here, we show that the metal–organic framework Fe 2 (dobdc) (dobdc 4− = 2,5-dioxido-1,4-benzenedicarboxylate) and its magnesium-diluted analogue, Fe 0.1 Mg 1.9 (dobdc), are able to activate the C–H bonds of ethane and convert it into ethanol and acetaldehyde using nitrous oxide as the terminal oxidant. Electronic structure calculations indicate that the active oxidant is likely to be a high-spin S = 2 iron( IV )–oxo species. Selective functionalization of light hydrocarbons is a challenging but desirable transformation. Now a family of Fe( II )-based metal–organic frameworks has been shown to convert ethane into ethanol and acetaldehyde using N 2 O. Electronic structure calculations indicate that the active Fe oxidant in the MOF is a high-spin S = 2 iron( II )–oxo species.