Solvent molecules influence the reactions of molecular hydrogen and oxygen on palladium nanoparticles. Organic solvents activate to form reactive surface intermediates that mediate oxygen reduction through pathways distinct from reactions in pure water. Kinetic measurements and ab initio quantum chemical calculations indicate that methanol and water cocatalyze oxygen reduction by facilitating proton-electron transfer reactions. Methanol generates hydroxymethyl intermediates on palladium surfaces that efficiently transfer protons and electrons to oxygen to form hydrogen peroxide and formaldehyde. Formaldehyde subsequently oxidizes hydrogen to regenerate hydroxymethyl. Water, on the other hand, heterolytically oxidizes hydrogen to produce hydronium ions and electrons that reduce oxygen. These findings suggest that reactions of solvent molecules at solid-liquid interfaces can generate redox mediators in situ and provide opportunities to substantially increase rates and selectivities for catalytic reactions.

We characterize a mechanism for a monomeric copper catalyst reported to oxidize water in bicarbonate solution when subject to sufficiently high external potentials at near neutral pH values.

The electronic structure of the [Cu3S2]3+ core of [(LCu)3(S)2]3+ (L = N,N,N′,N′-tetramethyl-2R,3R-cyclohexanediamine) is investigated using a combination of Cu and S K-edge X-ray absorption spectroscopy and calculations at the density functional and multireference second-order perturbation levels of theory. The results show that the [Cu3S2]3+ core is best described as having all copper centers close to, but more oxidized than, Cu2+, while the charge on the S2 fragment is between that of a sulfide (S2−) and a subsulfide (S23−) species. The [Cu3S2]3+ core thus is different from a previously described, analogous [Cu3O2]3+ core, which has a localized [(Cu3+Cu2+Cu2+)(O2−)2]3+ electronic structure. The difference in electronic structure between the two analogues is attributed to increased covalent overlap between the Cu 3d and S 3p orbitals and the increased radial distribution function of the S 3p orbital (relative to O 2p). These features result in donation of electron density from the S-S σ* to the Cu and result in some bonding interaction between the two S atoms at ~ 2.69 Å in [Cu3S2]3+, stabilizing a delocalized S=1 ground state.

An efficient synthetic route to the mono-endo-6-N,N-diethylcarbamoyl and bis-endo,endo-6,12-N,Ndiethylcarbamoyl derivatives of Tröger's base (TB), endo-7 and endo-8, is reported. Studies of reaction time, proton source, and additive allowed establishment of optimized conditions for the conversion of exo-7 into the corresponding isomer endo-7. With a longer reaction time, the exo,exo-6,12 bis-carbamoyl derivative exo-8 was converted into the corresponding endo,endo-bis-carbamoyl product endo-8. Single crystal X-ray crystallographic analysis confirmed the structural and stereochemical assignments made on the basis of 1 H NMR, mechanistic, and computational studies. Deuterium quench experiments using LDA, CD 3 ONa/CD 3 OD and DCl/CD 3 OD conditions of both exo-7 and exo-8 afforded exo-7d 1 and exo-8d 2 , respectively (> 95% deuterium incorporation), supporting an enolate mechanism for the isomerization. In contrast, when repeating the experiment with DCl/CD 3 OD, no deuterium was incorporated, suggesting the traditional ring-opening mechanism involving an iminium ion.

Correction for 'Mechanistic analysis of water oxidation catalyzed by mononuclear copper in aqueous bicarbonate solutions' by Stuart G. Winikoff et al., Catal. Sci. Technol., 2014, 4, 2484-2489 While all pK a values and reduction potentials in Fig. 1 of the original paper are correct, the equilibrium percentages reported for the speciation of compounds 1, 2, and 3 and for compounds 4, 6, and 8 that derive therefrom are not. Instead, the aqueous speciation of 1, 2, and 3 at pH = 8.2 should be listed as 60.7%, 36.8%, and 2.5%, respectively. The aqueous speciation of 4, 6, and 8 is not conveniently expressed in percentages; rather, the relative equilibrium free energies for these compounds in aqueous solution are 15.2, 7.2, and 0.0 kcal mol −1 , respectively. Assuming small barriers to incorporation/ release of water as a ligand, the replenishment of compound 4 from compound 8 will have an activation free energy about equal to that originally assigned to the rate-determining process in the catalytic cycle, namely, O-O bond formation leading to compound 13 (15.7 kcal mol −1 ).