We report a reinterpretation of the reduction of 4-nitrophenol catalyzed by silver nanoparticles. Mass spectrometry and ultraviolet−visible light spectroscopy measurements support the existence of 4-nitrosophenol as a stable reaction intermediate. We propose that dissolved oxygen is consumed, both by oxidizing 4nitrosophenol (an intermediate) and reoxidizing the reduced catalyst surface, resulting in the commonly observed "induction period" in the reaction kinetics. Upon complete consumption of dissolved oxygen, subsequent reduction to 4-aminophenol can occur. A complete kinetic analysis including modeling is presented, conceptually fitting data from recent reports in the literature, as well as fitting data from our own experiments.

Electronic probes of ligands, particularly carbenes, are widely used in assessing electronic properties; the results inform the selection of a ligand for a given application. As such, it is important to ensure the data obtained is reliable and unaffected by other factors, such as the steric bulk of the ligand. The effects of such steric factors on two commonly used electronic probes (based on palladium and selenium) are investigated here, with the selenium adduct found to be particularly sensitive. It is hoped that this serves as a cautionary tale to always critically evaluate what a probe is measuring.

The electronic properties of a series of imidazolium-derived N-heterocyclic carbenes systematically substituted at the 4,5-positions were investigated through NMR analysis of their palladium and selenone derivatives. This combined approach provided information on both the σ-donating ability and the π-accepting ability of the carbenes, allowing correlation with the electronic nature of the substituents on the carbene and providing an understanding of the structural features that affect these properties; in principle, this allows design of related ligands with known electronic parameters. Along with a greater understanding of the electronic properties of this series of carbenes, the work allows a comparison of the utility of both NMR probes based on the information gained, and the differences in requirements for preparation and acquisition. With this in mind, the selenone probe is proposed as being able to provide a wide range of electronic information, along with being relatively easily prepared.