The first examples of aziridination catalysis with a chromium complex are communicated. This tetracarbene chromium complex provides novel catalytic aziridination reactions with protic substrates such as alcohols or amines on the alkene or organic azide and is the most effective catalyst at low alkene loading for aliphatic alkenes to date.

Bismuth(III) vanadate (BiVO 4) films show activity for direct benzyl alcohol (PhCH 2 OH) oxidation to benzaldehyde (PhCHO) in acetonitrile solvent. Introducing tetrabutylammonium nitrate (Bu 4 NNO 3) drastically reduces the overpotential required to generate the PhCHO product while maintaining a high faradaic efficiency (FE) > 90 %. BiVO 4 corrosion accompanies PhCH 2 OH oxidation. However, the presence of nitrate ions (NO 3 À) results in significantly less bismuth-and vanadium-ion leaching (determined by ICP-MS analysis), as well as reduced surface roughening (determined by SEM imaging). In this reaction, it is proposed that rate-determining NO 3 À oxidation generates a highly reactive nitrate radical (NO 3 •) that reacts with PhCH 2 OH by hydrogen-atom abstraction (HAT). NO 3 À is stoichiometrically consumed by the irreversible formation of electrochemically inert HNO 3 , characterized by an EC i mechanism, rather than a catalytic EC' mechanism. In the presence of PhCH 2 OH, NO 3 À oxidation on BiVO 4 becomes more facile; every order of magnitude increase in PhCH 2 OH concentration shifts the NO 3 À / NO 3 • equilibrium potential negatively by 200 mV. The shift results from the introduction of a consumption pathway for the nitrate radical intermediate via a coupled chemical step with benzyl alcohol. This report is the first example of photoelectrochemical NO 3 • generation to initiate indirect PhCH 2 OH oxidation.

Nitrate anion (NO3 –) oxidation to nitrate radical (NO3 •) is chemically irreversible in acetonitrile (MeCN) solvent due to solvent-based hydrogen-atom transfer (HAT). Introducing benzyl alcohol (PhCH2OH) leads to competition with MeCN for electrochemically generated NO3 • and affords benzaldehyde (PhCHO) product with ∼80% faradaic efficiency (FE) in 250 mM PhCH2OH. Stoichiometric HNO3 forms during HAT reactions (observed by UV–vis spectroscopy) and exists as an electrochemically inert and weak electrolyte; this off-cycle form of nitrate can be reintroduced to the catalytic cycle upon deprotonation by 2,6-lutidine while maintaining the base-free FE. Oxygen reduction complements nitrate oxidation during catalysis and reduced oxygen species (ROS) generated during proton-coupled oxygen reduction are identified through rotating ring-disk electrochemistry; proton-coupled oxygen reduction indicates ROS are capable of rendering NO3 – catalytic when collocal. Directly observing ROS as the stoichiometric base generated during nitrate anion oxidation resolves differences in photocatalytic vs photoelectrochemical reactivity of NO3 – in base-free conditions and points toward HAT as the general mode of reactivity for nitrate radical in acetonitrile solutions.