Direct Visualization of the Chemical Mechanism in SERRS of 4‐Aminothiophenol/Metal Complexes and Metal/4‐Aminothiophenol/Metal Junctions

Direct visualization of photoinduced tunneling charge transfer (TCT) in an Au₅/para‐aminothiophenol (PATP)/Ag₆ junction in which Au and Ag clusters form the first and second layer, respectively, is provided by the charge difference density (see picture; green and red stand for holes and electrons, respectively).

     

Synthesis of Heterocyclic Compounds Catalyzed by Metal/Metal Oxide‐Multiwall Carbon Nanotube Nanocomposites

Metal/metal oxide‐decorated multiwalled carbon nanotubes (MWCNTs ) have been found to be effective over various catalysts because of the synergistic, hybrid, physical, and chemical properties of such nanotubes. These properties make them highly active catalytic tools with excellent chemoselectivity, low catalyst loading, and high recyclability of the catalyst. Here, we discuss some recent findings related to the following topics: (1) synthesis of metal/metal oxide‐decorated MWCNTs , (2) characterization techniques of heterogeneous nanocomposites, and (3) application of these metal/metal oxide nanocomposites for the synthesis of heterocyclic compounds. This review emphasizes the main requirements for developing new nanocomposites for the synthesis of pharmaceutically important heterocycles.     

The Characterization of Molecular Alkali‐Metal Azides.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Identification of Catalytic Sites for Oxygen Reduction in Metal/Nitrogen‐Doped Carbons with Encapsulated Metal Nanoparticles

The development of metal‐N‐C materials as efficient non‐precious metal (NPM) catalysts for catalysing the oxygen reduction reaction (ORR) as alternatives to platinum is important for the practical use of proton exchange membrane fuel cells (PEMFCs). However, metal‐N‐C materials have high structural heterogeneity. As a result of their high‐temperature synthesis they often consist of metal‐N_x sites and graphene‐encapsulated metal nanoparticles. Thus it is hard to identify the active structure of metal‐N‐C catalysts. Herein, we report a low‐temperature NH₄Cl‐treatment to etch out graphene‐encapsulated nanoparticles from metal‐N‐C catalysts without destruction of co‐existing atomically dispersed metal‐N_x sites. Catalytic activity is much enhanced by this selective removal of metallic nanoparticles. Accordingly, we can confirm the spectator role of graphene‐encapsulated nanoparticles and the pivotal role of metal‐N_x sites in the metal‐N‐C materials for ORR in the acidic medium.     

Metal/Metal Redox Isomerism Governed by Configuration

A pair of diastereomeric dinuclear complexes, [Tp′(CO)BrW{μ-η²-C,C′-κ²-S,P-C₂(PPh₂)S}Ru(η⁵-C₅H₅)(PPh₃)], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side-on carbon P,S-chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like-isomer is oxidized at W while the unlike-isomer is oxidized at Ru, which is proven by IR, NIR and EPR-spectroscopy supported by spectro-electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step. Finally, the tipping point could be realized in the unlike isomer of the electronically tuned thiophenolate congener [Tp′(CO)(PhS)W{μ-η²-C,C′-κ²-S,P-C₂(PPh₂)S}Ru(η⁵-C₅H₅)-(PPh₃)], in which valence trapped W^III/Ru^II and W^II/Ru^III cationic species are at equilibrium.     

Revisiting the Electroplating Process for Lithium‐Metal Anodes for Lithium‐Metal Batteries

Electroplating has been studied for centuries, not only in the laboratory but also in industry for machinery, electronics, automobile, aviation, and other fields. The lithium‐metal anode is the Holy Grail electrode because of its high energy density. But the recyclability of lithium‐metal batteries remains quite challenging. The essence of both conventional electroplating and lithium plating is the same, reduction of metal cations. Thus, industrial electroplating knowledge can be applied to revisit the electroplating process for lithium‐metal anodes. In conventional electroplating, some strategies like using additives, modifying substrates, applying pulse current, and agitating electrolyte have been explored to suppress dendrite growth. These methods are also effective in lithium‐metal anodes. Inspired by that, we revisit the fundamental electroplating theory for lithium‐metal anodes in this Minireview, mainly drawing attention to the theory of electroplating thermodynamics and kinetics. Analysis of essential differences between traditional electroplating and plating/stripping of lithium‐metal anodes is also presented. Thus, industrial electroplating knowledge can be applied to the electroplating process of lithium‐metal anodes to improve commercial lithium‐metal batteries and the study of lithium plating/stripping can further enrich the classical electroplating technique.     

Synergistic Catalysis: Metal/Proton‐Catalyzed Cyclization of Alkynones Toward Bicyclo[3.n.1]alkanones

A highly efficient and practical synergistically metal/proton‐catalyzed Conia–ene reaction for the synthesis of bicyclo[3.n.1]alkanones has been developed. This synergistic catalysis was successfully utilized in modifying natural compounds such as methyl dihydrojasmonate, α,β‐thujone, and 5α‐cholestan‐3‐one. Furthermore, the bridged carbonyl group of bicyclo[3.2.1]alkanones could be easily attacked by nucleophiles to give the ring‐opened cycloheptenone products or bicyclo[4.2.1]amide in excellent yields. These reactions provide rapid access to a diverse range of cyclic structures from simple starting materials or naturally occurring compounds.     

Transition‐Metal Nitride Core@Noble‐Metal Shell Nanoparticles as Highly CO Tolerant Catalysts

Core–shell architectures offer an effective way to tune and enhance the properties of noble‐metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core–shell carbide material (Pt/TiWC). X‐ray photoelectron spectroscopy revealed significant core‐level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d‐states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. The ability to control shell coverage and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties.     

Rare‐Earth‐Metal Methylidene Complexes

Transition‐metal carbene complexes have been known for about 50 years and widely applied as reagents and catalysts in organic transformations. In contrast, the carbene chemistry of the rare‐earth metals is much less developed, but has attracted the research interest in the recent years. In this field rare‐earth‐metal alkylidene, especially methylidene, compounds are an emerging class of compounds with a high synthetic potential for organometallic chemistry and maybe in the future also for organic chemistry.