Starting from furfural, maleic acid is efficiently synthesized in two steps under very mild conditions. In the first step, 5-hydroxy-2(5H)-furanone is synthesized via photochemical oxidation and proposed as a stable intermediate. Subsequent oxidation in the second step, by either an electrochemical or enzymatic process, results in maleic acid in high yield and selectivity.

Protic NHC iridium complexes, obtained from the corresponding azido-phenylene-isocyanide precursor complexes, were investigated for ligand-based reactivity. Under redox-neutral conditions, acetonitrile inserts into the N−H bonds to provide κ 2 -NHC-imidoyl ligand-based complexes, while under reductive conditions the complex also expels one N−H proton to provide the corresponding deprotonated analogues. Using zinc as a reductor activates the NHC-iridium complex to form an asymmetric bimetallic iridium hydrido complex, in which two anionic N-deprotonated NHCs bridge the bimetallic core. X-ray crystal structures are reported for the azido-phenylene-isocyanide precursor complex, the protic NHC complex, and the asymmetric bimetallic iridium hydride complex. Density functional computations and a QTAIM analysis of the bimetallic iridium hydrido complex are provided.