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Abstract: The sodium oxygen battery is a promising metal–air battery; however, the discharge process is not well understood and the major discharge product is still under debate. The discharge products determined the theoretical specific energy and electrochemical performance of the battery. Now it is demonstrated that NaO2 spontaneously disproportionates to Na2O2, no matter whether it is dissolved in solution or stays on the surface. The behaviors of NaO2 in solution and on the surface are different. Solvents play a crucial effect on the disproportionation of dissolved NaO2 species, which is fast in low donor number (DN) solvents such as acetonitrile but sluggish in high DN solvents such as DMSO. In situ XRD results exhibited the different product growing processes in various solvents. Surface NaO2 would slowly disproportionate to Na2O2 anyway, but this process is relatively slow compared to the time span of discharge process and it does not affect the major product on discharge. [ABSTRACT FROM AUTHOR]

The encumbered tetraisocyanide dianion Na2[Fe(CNAr [ABSTRACT FROM AUTHOR]

Pincer-type complexes [OsH2(CO){PyCH2NHCH2CH2NHP tBu2}] and [OsH2(CO){HN(CH2CH2P iPr2)2}] catalyze the disproportionation reaction of aldehydes via an outer-sphere bifunctional mechanism achieving turnover frequencies up to 14 000 h−1. The N−H group of the catalysts is a key player in this process, elucidated with the help of DFT calculations. [ABSTRACT FROM AUTHOR]

Impurity-doping in nanocrystals significantly affects their electronic properties and diversifies their applications. Herein, we report the synthesis of transition metal (Mn, Ni, Co, Cu)-doped oleophilic silicon nanocrystals (SiNCs) through hydrolysis/polymerization of triethoxysilane with acidic aqueous metal salt solutions, followed by thermal disproportionation of the resulting gel into a doped-Si/SiO2 composite that, upon HF etching and hydrosilylation with 1- n-octadecene, produces free-standing octadecyl-capped doped SiNCs (diameter≈3 to 8 nm; dopant <0.2 atom %). Metal-doping triggers a red-shift of the SiNC photoluminescence (PL) of up to 270 nm, while maintaining high PL quantum yield (26 % for Co doping). [ABSTRACT FROM AUTHOR]

A perovskite-structure oxide containing unusually high-valence Fe3.5+ was obtained by high-pressure synthesis. Instability of the Fe3.5+ in Ca0.5Bi0.5FeO3 is relieved first by charge disproportionation at 250 K and then by intermetallic charge transfer between A-site Bi and B-site Fe at 200 K. These previously unobserved successive charge transitions are due to competing intermetallic and disproportionation charge instabilities. Both transitions change magnetic and structural properties significantly, indicating strong coupling of charge, spin, and lattice in the present system. [ABSTRACT FROM AUTHOR]

The transition metal tetra- and trinorbornyl bromide complexes, M(nor)4 (M=Fe, Co, Ni) and Ni(nor)3Br (nor=1-bicyclo[2.2.1]hept-1-yl) and their homolytic fragmentations were studied computationally using hybrid density functional theory (DFT) at the B3PW91 and B3PW91-D3 dispersion-corrected levels. Experimental structures were well replicated; the dispersion correction resulted in shortened M−C bond lengths for the stable complexes, and it was found that Fe(nor)4 receives a remarkable 45.9 kcal mol−1 stabilization from the dispersion effects whereas the tetragonalized Co(nor)4 shows stabilization of 38.3 kcal mol−1. Ni(nor)4 was calculated to be highly tetragonalized with long Ni−C bonds, providing a rationale for its current synthetic inaccessibility. Isodesmic exchange evaluation for Fe(nor)4 confirmed that dispersion force attraction between norbornyl substituents is fundamental to the stability of these species. [ABSTRACT FROM AUTHOR]

The synthesis of the first linear coordinated CuII complex Cu{N(SiMe3)Dipp}2 ( 1 Dipp=C6H5-2,6Pr i2) and its CuI counterpart [Cu{N(SiMe3)Dipp}2]− ( 2) is described. The formation of 1 proceeds through a dispersion force-driven disproportionation, and is the reaction product of a CuI halide and LiN(SiMe3)Dipp in a non-donor solvent. The synthesis of 2 is accomplished by preventing the disproportionation into 1 by using the complexing agent 15-crown-5. EPR spectroscopy of 1 provides the first detailed study of a two-coordinate transition-metal complex indicating strong covalency in the Cu−N bonds. [ABSTRACT FROM AUTHOR]

An experimental and theoretical study of the base-stabilized disilene 1 is reported, which forms at low temperatures in the disproportionation reaction of Si2Cl6 or neo-Si5Cl12 with equimolar amounts of NMe2Et. Single-crystal X-ray diffraction and quantum-chemical bonding analysis disclose an unprecedented structure in silicon chemistry featuring a dative Si→Si single bond between two silylene moieties, Me2EtN→SiCl2→Si(SiCl3)2. The central ambiphilic SiCl2 group is linked by dative bonds to the amine donor and the bis(trichlorosilyl)silylene acceptor, which leads to push-pull stabilization. Based on experimental and theoretical examinations a formation mechanism is presented that involves an autocatalytic reaction of the intermediately formed anion Si(SiCl3)3− with neo-Si5Cl12 to yield 1. [ABSTRACT FROM AUTHOR]

The disproportionation of elemental sulfur at moderate temperatures is investigated in the redox condensation involving o-halonitrobenzenes 1 and benzylamines 2. As a redox moderator, elemental sulfur plays the dual role of both electron donor and acceptor, generating its lowest and highest oxidation states: S−2 (sulfide equivalent) in benzothiazole 3 and S+6 (sulfate equivalent) in sulfamate 4, and filling the electron gap of the global redox condensation process. Along with this process, a cascade of reactions of reduction of the nitro group of 1, oxidation of the aminomethyl group of 2, metal-free aromatic halogen substitution, and condensation finally led to 2-arylbenzothiazoles 3. [ABSTRACT FROM AUTHOR]

A robust catalyst for the selective dehydrogenation of formic acid to liberate hydrogen gas has been designed computationally, and also successfully demonstrated experimentally. This is the first such catalyst not based on transition metals, and it exhibits very encouraging performance. It represents an important step towards the use of renewable formic acid as a hydrogen-storage and transport vector in fuel and energy applications. [ABSTRACT FROM AUTHOR]

The disproportionation of formic acid to methanol was unveiled in 2013 using iridium catalysts. Although attractive, this transformation suffers from very low yields; methanol was produced in less than 2% yield, because the competitive dehydrogenation of formic acid (to CO2 and H2) is favored. We report herein the efficient and selective conversion of HCOOH to methanol in 50%yield, utilizing ruthenium(II) phosphine complexes under mild conditions. Experimental and theoretical (DFT) results show that different convergent pathways are involved in the production of methanol, depending on the nature of the catalyst. Reaction intermediates have been isolated and fully characterized and the reaction chemistry of the resulting ruthenium complexes has been studied. [ABSTRACT FROM AUTHOR]

Attraktive Modelle: Synthetische ZnII ‐ Komplexe wurden als Modelle der Kupfer ‐ Zink ‐ Superoxid ‐ Dismutase erforscht. Superoxid geht eine spezielle Disproportionierungsreaktion innerhalb der elektrostatischen Kugel der Komplexe ein (siehe Bild; bpy=2,2′ ‐ Bipyridyl). Die Aktivität der ZnII ‐ Komplexe für die Induktion der Superoxid ‐ Disproportionierung hängt von der Lewis ‐ Acidität und der Koordinationsgeometrie des Zn ‐ Zentrums ab. [ABSTRACT FROM AUTHOR]