Structural and Spectroscopic Characterization of a High‐Spin {FeNO}6 Complex with an Iron(IV)−NO− Electronic Structure

Although the interaction of low‐spin ferric complexes with nitric oxide has been well studied, examples of stable high‐spin ferric nitrosyls (such as those that could be expected to form at typical non‐heme iron sites in biology) are extremely rare. Using the TMG₃tren co‐ligand, we have prepared a high‐spin ferric NO adduct ({FeNO}⁶ complex) via electrochemical or chemical oxidation of the corresponding high‐spin ferrous NO {FeNO}⁷ complex. The {FeNO}⁶ compound is characterized by UV/Visible and IR spectroelectrochemistry, Mössbauer and NMR spectroscopy, X‐ray crystallography, and DFT calculations. The data show that its electronic structure is best described as a high‐spin iron(IV) center bound to a triplet NO^? ligand with a very covalent iron?NO bond. This finding demonstrates that this high‐spin iron nitrosyl compound undergoes iron‐centered redox chemistry, leading to fundamentally different properties than corresponding low‐spin compounds, which undergo NO‐centered redox transformations.     

Synthesis of α‐Fluoroketones by Insertion of HF into a Gold Carbene

Reported is an efficient synthesis of α‐fluoroketones by insertion of hydrogen fluoride (HF) into the gold carbene intermediate, generated from a cationic gold catalyzed addition of N‐oxides to alkynes. This method results in excellent chemical yields for a wide range of alkyne substrates and demonstrates good functional‐group tolerance.     

An Aurivillius Oxide Based Cathode with Excellent CO2 Tolerance for Intermediate‐Temperature Solid Oxide Fuel Cells

The Aurivillius oxide Bi₂Sr₂Nb₂MnO_12?δ (BSNM) was used as a cobalt‐free cathode for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). To the best of our knowledge, the BSNM oxide is the only alkaline‐earth‐containing cathode material with complete CO₂ tolerance that has been reported thus far. BSNM not only shows favorable activity in the oxygen reduction reaction (ORR) at intermediate temperatures but also exhibits a low thermal expansion coefficient, excellent structural stability, and good chemical compatibility with the electrolyte. These features highlight the potential of the new BSNM material as a highly promising cathode material for IT‐SOFCs.     

Influence of Metal Oxides on Platinum Activity towards Methanol Oxidation in H2SO4 solution

Pt–CeO₂/C, Pt–TiO₂/C, and Pt–ZrO₂/C electrocatalysts were prepared by using a modified microwave‐assisted polyol process. Physical characterization was performed by using XRD, TEM, and EDX analyses. The incorporation of different metal oxides increased the dispersion degree of Pt nanoparticles and reduced their diameter to 2.50 and 2.33 nm when TiO₂ and ZrO₂ were introduced to Pt/C, respectively. The electrocatalytic activity of various electrocatalysts was examined towards methanol oxidation in H₂SO₄ solution by using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Among the studied composites, Pt–ZrO₂/C was selected to be a candidate electrocatalyst for better electrochemical performance in direct methanol fuel cells.     

Phosphorus-based allenes as scaffolds in cycloaddition and cyclization reactions

ABSTRACT

In this article, we describe some of our results on the reactions of allenylphosphonates/allenyl phosphine oxides and allenyl diazaphosphole oxides, primarily cycloaddition and cyclization reactions. Depending on the substituents, both the α,β and β,γ -cycloaddition products have been observed. A novel cyclization reaction of a functionalized allenylphosphine oxide with diethylamine leading to 3-diethylamino-4-diphenylphosphinoyl-1-naphthol is reported. Representative compounds have been characterized by X-ray crystallography.     

Titanium-based mixed oxides from a series of titanium(IV) citrate complexes

The isostructural hexaaquatransition-metal/titanium citrate complexes (NH₄)₂[M(H₂O)₆][Ti(H₂cit)₃]₂·6H₂O [M(II)=Mn 1, Fe 2, Co 3, Ni 4, Cu 5, and Zn 6] (H₄cit=citric acid), which were synthesized by reacting titanium(IV) citrate with divalent metal salts in the 1.0-3.5 pH range, adopt hydrogen-bonded chain motifs. The crystal structures feature three bidentate citrate anions that chelate to the titanium atom through their negatively charged α-alkoxy and α-carboxy oxygen atoms; the chelation is consistent with the large downfield shifts of ¹³C NMR for carbon atoms for complex 6. The thermal decomposition of the complexes furnishes mixed metal oxides. The main-group magnesium analog when heated at 600 °C yielded MgTi₂O₅ that is of the pseudobrookite type; the particle size is approximately 30 nm.