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Dilute PdAu alloys are promising catalysts for selective oxidation with high activity and high selectivity. The promotional effect of Pd for selective alcohol oxidation is strongly dependent on the alkyl chain length. Whereas Pd substantially promotes the selective oxidation of methanol, there is essentially no promotion of oxidation of longer-chain alcohols (C2–C4) for Pd3Au97 RCT-SiO2 compared to pure Au RCT-SiO2. The lack of promotion of selective oxidation of higher alcohols by Pd is attributed to their over-oxidation on the Pd3Au97 RCT-SiO2 catalyst, yielding strongly bound carboxylates that poison the Pd sites. The longer-chain carboxylates are stable on the surface under reaction conditions whereas formate, which would form from over-oxidation of methanol, decomposes. The surface carboxylate was identified for 1-propanol oxidation as propionate using in situ Fourier transform infrared (FTIR) spectroscopy. Further evidence for poisoning by carboxylates is the production of CO2 in temperature programmed oxidation following catalyst use. The poisoned catalyst can be regenerated in a flowing methanol/oxygen mixture, restoring the promotional effect of Pd for methanol oxidation. The residual activity of the Au and of the poisoned Pd/Au catalysts may be due to the migration of hydroxyl from the silica support to the nanoparticle. A reservoir of hydroxyl groups on the RCT-SiO2 is identified using FTIR. Hydroxyls on Au are known to spontaneously disproportionate to adsorbed oxygen atoms and water. These results demonstrate the sensitivity of dilute alloy catalyst reactivity to molecular structure. [ABSTRACT FROM AUTHOR]

Supported Au–Pd nanoparticles with low Pd content (between 2% and 25%) are excellent catalysts for the selective hydrogenation of alkynes into alkenes, a crucial step for elimination of alkynes from the reactants for olefin polymerization. They have better selectivity at high conversions for the hydrogenation of 1-hexyne to 1-hexene compared to that of pure Pd. However, the role of Pd concentration in Au–Pd particles in maximizing the activity per gram of Pd remains elusive. This work combines scanning transmission electron microscopy (STEM) and density functional theory (DFT) to determine how Pd concentration in the dilute limit affects the activity and selectivity of Au–Pd particles for the hydrogenation of acetylene. Atomic resolution microscopy shows increased Pd segregation to the surface with increasing Pd concentration (above 9%), and DFT analysis shows that isolated Pd atoms on the Au–Pd surface are highly active for acetylene hydrogenation compared to Pd atoms adjacent to other Pd atoms. A high concentration of isolated and active Pd atoms combined with increased segregation of Pd toward the surface explains the existence of an optimum for catalytic properties. It explains the high performance of Au0.96Pd0.04 compared to Au–Pd particles with lower or higher Pd concentrations. [ABSTRACT FROM AUTHOR]

Living organisms have unique homeostatic abilities, maintaining tight control of their local environment through interconversions of chemical and mechanical energy and self-regulating feedback loops organized hierarchically across many length scales [...]

Synthesis of a series of facial (methyl)(hydrido)(silyl) complexes of Ir(III) and the determination of their X-ray structure enable the arrangement of CH3, H, SiPh3, and SiEt3 ligands according to their trans influence. The compounds studies are L3Ir(CH3)(H)(SiR3), where L=PMe3, and the variable R represents EtO, Ph, or Et in the three compounds.

A rhodium complex initiates a reaction involving removal of a methylene (CH2) group from a methyl (CH3) group and subsequent insertion into different bonds, such as Si-H, Si-Si and C-H. This transfer of methylene group indicates the probability of functionalization of an unstrained carbon-carbon single bond through hydrosilylation. Thermodynamics influence these reactions in a positive manner.

Abstract: The developing field of active, stimuli‐responsive materials is in need for new dynamic architectures that may offer unprecedented chemomechanical switching mechanisms. Toward this goal, syntheses of polymerizable bipyridine ligands, bis(4‐vinylbenzyl)[2,2′‐bipyridine]‐4,4′‐dicarboxylate and N4,N4′‐bis(4‐vinylphenyl)‐2,2′‐bipyridine‐4,4′‐dicarboxamide, and a number of redox‐active Ruthenium(II) and Iron(II) complexes with them are reported. Detailed characterizations by NMR, Fourier transform infrared spectroscopy, high‐resolution mass‐spectrometry, X‐ray, and cyclic voltammetry show that the topology of these molecules allows them to serve as both comonomers and crosslinkers in polymerization reactions. Electronic properties of the ligands are tunable by choosing carboxylate‐ or carboxamido‐linkages between the core and the vinylaryl moieties, leading to a library of Ru and Fe complexes with the M(III)/M(II) standard redox potentials suitable for catalyzing self‐oscillating Belousov–Zhabotinskii (BZ) reaction. New poly(N‐isopropylacrylamide)‐based redox‐responsive functional gels containing hydrophilic comonomers, which have been prepared using representative Ru bpy complexes as both a crosslinker and redox‐active catalyst, exhibit a unique feature: their swelling/contraction mode switches its dependence on the oxidation state of the Ru center, upon changing the ratio of comonomers in the hybrid gel network. The BZ self‐oscillations of such crosslinked hydrogels have been observed and quantified for both supported film and free‐standing gel samples, demonstrating their potential as chemomechanically active modules for new functional materials. [ABSTRACT FROM AUTHOR]

Abstract: A highly modular synthesis of designed catalysts with controlled bimetallic nanoparticle size and composition and a well‐defined structural hierarchy is demonstrated. Exemplary catalysts—bimetallic dilute Ag‐in‐Au nanoparticles partially embedded in a porous SiO2 matrix (SiO2–AgxAuy)—were synthesized by the decoration of polymeric colloids with the bimetallic nanoparticles followed by assembly into a colloidal crystal backfilled with the matrix precursor and subsequent removal of the polymeric template. This work reports that these new catalyst architectures are significantly better than nanoporous dilute AgAu alloy catalysts (nanoporous Ag3Au97) while retaining a clear predictive relationship between their surface reactivity with that of single‐crystal Au surfaces. This paves the way for broadening the range of new catalyst architectures required for translating the designed principles developed under controlled conditions to designed catalysts under operating conditions for highly selective coupling of alcohols to form esters. Excellent catalytic performance of the porous SiO2–AgxAuy structure for selective oxidation of both methanol and ethanol to produce esters with high conversion efficiency, selectivity, and stability was demonstrated, illustrating the ability to translate design principles developed for support‐free materials to the colloid‐templated structures. The synthetic methodology reported is customizable for the design of a wide range of robust catalytic systems inspired by design principles derived from model studies. Fine control over the composition, morphology, size, distribution, and availability of the supported nanoparticles was demonstrated. [ABSTRACT FROM AUTHOR]