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Oxidation is a powerful methodology that is widely used for the production of fine chemicals and pharmaceutical intermediates, however, this process often involves the use of toxic reagents and harsh reaction conditions. Herein we report an efficient and eco-friendly way to promote the aerobic oxidation of organic halides to aldehydes/ketones and oxidative coupling of amines to imines using an inorganic-ligand supported iron catalyst 1a (NH4)3[FeMo6O18(OH)6] with O2 (1 atm) as the sole oxidant. 1a is synthesized directly from cheap and commonly available (NH4)6Mo7O24·4H2O and Fe2(SO4)3, which consist of a pure inorganic framework built from a central FeIII core supported by six MoVIO6 inorganic scaffolds. The iron catalyst 1a exhibits better activity towards a wide range of substrates in the catalytic oxidation of halides and amines, and the use of toxic oxidants and potentially air/moisture sensitive and complicated organic ligands that are not commercially available is avoided. Owing to the robust inorganic framework, 1a shows good stability and reusability and the catalytic oxidation of halides and amines could be readily scaled up to gram-scale with little loss of catalytic activity, demonstrating the great potential of inorganic-ligand supported catalysts in catalytic chemical transformation.

Formamides represent an abundant class of compounds in organic synthesis. They can be made efficiently by the direct catalytic coupling of methanol with amines in the presence of metal-based catalysts. However, these catalysts require complicated organic ligands, susceptible to oxidative self-degradation, restricting their practical applications. Here, we describe an inorganic ligand-supported chromium (III) catalyst, (NH4)3[CrMo6O18(OH)6], which consists of a central chromium (III) single-atomic core supported by a cycle-shaped inorganic ligand consisting of six MoVIO6 octahedra, shows excellent activity and selectivity. Various primary amines and secondary amines are successfully transformed into the corresponding formamides under mild conditions, and the formylation of primary diamines is also achieved. The chromium catalyst can be reused several times with little loss of the activity. Mechanistic insight is provided based on the observation of an intermediate and control experiments. Several catalytic methods for N-formylation of amines using noble metals or manganese pincer complexes are known. Here an air-stable and reusable chromium-based polyoxometalate is shown to catalyze the N-formylation of amines and diamines using methanol and hydrogen peroxide.