The selective oxidation of light hydrocarbons and their valorization with only dioxygen (O2) are important transformations toward development of efficient chemical processes. Monooxygenase enzymes can catalyze selective aerobic reactions under reducing and protic conditions. The translation of such enzymatic pathways to the practical electrocatalytic oxidation of light, gaseous hydrocarbons, using O2 as sole oxidant is now reported. An iron–tungsten oxide inorganic molecular catalyst with a capsular structure {Fe30W72} stabilized inside by sulfate/bisulfate anions provides a protic environment where three iron atoms are located at each of the pores of the capsule leading to a unique and potent active site for the oxidation reactions. Under mild electrochemical conditions, 1.8 V, in water at room temperature, using O2 from air, we demonstrate the low-pressure (1–2 bar) hydroxylation of alkanes, notably ethane to acetic acid, and the ozone like cleavage of the carbon–carbon double bonds of alkenes. Typical turnover frequencies were 300–400 min–1. Initial mechanistic studies support a reaction through a very active iron-oxo species.

The reductive activation of molecular oxygen catalyzed by iron-based enzymes toward its use as an oxygen donor is paradigmatic for oxygen transfer reactions in nature. Mechanistic studies on these enzymes and related biomimetic coordination compounds designed to form reactive intermediates, almost invariably using various “shunt” pathways, have shown that high-valent Fe­(V)O and the formally isoelectronic Fe­(IV)O porphyrin cation radical intermediates are often thought to be the active species in alkane and arene hydroxylation and alkene epoxidation reactions. Although this four decade long research effort has yielded a massive amount of spectroscopic data, reactivity studies, and a detailed, but still incomplete, mechanistic understanding, the actual reductive activation of molecular oxygen coupled with efficient catalytic transformations has rarely been experimentally studied. Recently, we found that a completely inorganic iron–tungsten oxide capsule with a keplerate structure, noted as {Fe30W72}, is an effective electrocatalyst for the cathodic activation of molecular oxygen in water leading to the oxidation of light alkanes and alkenes. The present report deals with extensive reactivity studies of these {Fe30W72} electrocatalytic reactions showing (1) arene hydroxylation including kinetic isotope effects and migration of the ipso substituent to the adjacent carbon atom (“NIH shift”); (2) a high kinetic isotope effect for alkyl CH bond activation; (3) dealkylation of alkylamines and alkylsulfides; (4) desaturation reactions; (5) retention of stereochemistry in cis-alkene epoxidation; and (6) unusual regioselectivity in the oxidation of cyclic and acyclic ketones, alcohols, and carboxylic acids where reactivity is not correlated to the bond disassociation energy; the regioselectivity obtained is attributable to polar effects and/or entropic contributions. Collectively these results also support the conclusion that the active intermediate species formed in the catalytic cycle is consistent with a compound I type oxidant. The activity of {Fe30W72} in cathodic aerobic oxidation reactions shows it to be an inorganic functional analogue of iron-based monooxygenases.

First row transition metal substituted polyfluorooxmetalates with quasi Wells-Dawson structures and a nitro terminal ligand, [NaH2M(NO2)W17F6O55](q-), were used as catalysts for the aerobic epoxidation of cyclic alkenes. The Cu(NO2) analog combined the best traits of conversion and selectivity. Some C-C bond cleavage was also observed and cis isomers reacted preferentially without stereochemical inversion indicating an oxygen atom to double bond concerted reaction.

Polyfluoroxometalates (PFOMs) that have a quasi Wells-Dawson structure and have low valent transition metal substitution at the so-called "belt" position, α 1 -[H 2 F 6 NaM-(H 2 O)W 17 O 55 ] q-, can reversibly interchange between dimeric and monomeric structures. The dimers have two unique M-μO-W bridges between two PFOM units. The dimerization occurs through dehydration and was studied as a function of temperature using the visible spectrum that is sensitive to the wavelength and extinction coefficient of the d-d transition. The [a]