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A variety of metal oxides can catalyze the oxidation of water to molecular oxygen when polarized by a sufficiently high electrochemical potential. Minimizing the overpotential and increasing the rate of the oxygen-evolving reaction (OER) are key goals in making such materials a component of viable energy storage devices. However, the structural factors that imbue the metal oxides with their catalytic power are difficult to assess as these solids contain many distinct metal-ion sites, have a varying amount of defect sites within the lattice, and can be composed of multiple phases. In the present study, we determined the magnetic properties for a series of dimeric cobalt complexes in which the two metal centers are bridged by a dioxygen moiety. Our spectroscopically validated electronic structure description indicates that each species is best described as two Co(III) ions that are bound to a μ–η1η1 superoxide ligand. Intriguingly, we found evidence that the two compounds that possess oxygen-evolving activi...

Palladium(II)-catalyzed aerobic oxidative cyclization of alkenes with tethered tert-butanesulfinamides furnishes enantiopure 2,5-disubstituted pyrrolidines, originating from readily available and easily diversified starting materials. These reactions are the first reported examples of metal-catalyzed addition of sulfinamide nucleophiles to alkenes.

This study seeks to explore the effects of the electronic structure of Pt/Ru alloy nanoparticles on reactivity of small organic molecules of relevance to fuel cell applications through the combined use of synchrotron radiation photoelectron spectroscopy and electrochemistry. Platinum core-level binding energies were found to increase linearly with the addition of ruthenium. This effect is a product of lattice strain and charge transfer, and is explained in terms of the d-band center theory proposed by Norskov and co-workers (Hammer, B.; Norskov, J. K. Surf. Sci. 1995, 343, 211). In the course of the study of electrooxidation of methanol we have found that it is very difficult, if not impossible, to separate the effects of the bifunctional mechanism and the electronic structure effects that might play a role in the activity. However, data for electrooxidation of formic acid, when studied at a short reaction time (where the indirect reaction pathways and poisoning intermediates are assumed to play a negligi...

The surface structure, stability, and electrocatalytic activity of the Pt3Co alloy toward oxygen reduction reaction (ORR) (with reference to Pt black) in both alkaline and acidic media were studied by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry, and by the rotating disk electrode method. The XPS data show that two species of cobalt, metallic cobalt and cobalt oxides, coexist in the as-received Pt3Co sample. In combination with the voltammetric results, the XPS data demonstrate that there is dissolution of cobalt upon exposure of the sample to acidic media, whereas the cobalt forms in the catalyst are stable in alkaline media. In addition, the Pt 4f binding energy was found by XPS to be upshifted by 0.2 eV vs that of the pure Pt black reference. In acids, Pt3Co alloy has a slightly but demonstratively higher activity than Pt black toward the oxygen reduction reaction as shown by the positive half-wave potential shift of ca. 10 ± 2 mV, while in alkaline media a decrease in the ORR activity wa...

The manganese(III)-bis[poly(pyrazolyl)borate] complexes, Mn(pzb)2SbF6, where pzb- = tetrakis(pyrazolyl)borate (pzTp) (1), hydrotris(pyrazolyl)borate (Tp) (2), or hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) (3), have been synthesized by oxidation of the corresponding Mn(pzb)2 compounds with NOSbF6. The Mn(III) complexes are low-spin in solution and the solid state (μeff = 2.9−3.8 μB). X-ray crystallography confirms their uncommon low-spin character. The close conformity of mean Mn−N distances of 1.974(4), 1.984(5), and 1.996(4) A in 1, 2, and 3, respectively, indicates absence of the characteristic Jahn−Teller distortion of a high-spin d4 center. N−Mn−N bite angles of slightly less than 90o within the facially coordinated pzb- ligands produce a small trigonal distortion and effective D3d symmetry in 1 and 2. These angles increase to 90.0(4)o in 3, yielding an almost perfectly octahedral disposition of N donors in Mn(Tp*)2+. Examination of structural data from 23 metal−bis(pzb) complexes reveals systematic...