Selective partial oxidation of methane to methanol suffers from low efficiency. Here, we report a heterogeneous catalyst system for enhanced methanol productivity in methane oxidation by in situ generated hydrogen peroxide at mild temperature (70°C). The catalyst was synthesized by fixation of AuPd alloy nanoparticles within aluminosilicate zeolite crystals, followed by modification of the external surface of the zeolite with organosilanes. The silanes appear to allow diffusion of hydrogen, oxygen, and methane to the catalyst active sites, while confining the generated peroxide there to enhance its reaction probability. At 17.3% conversion of methane, methanol selectivity reached 92%, corresponding to methanol productivity up to 91.6 millimoles per gram of AuPd per hour.

Xiao and colleagues successfully designed a powerful siliceous zeolite support and a core-shell structure, which is achieved by fixing RhMn nanoparticles within Silicate-1 zeolite crystals (RhMn@S-1), could remarkably boost the ethanol production from direct syngas conversion. C 2 -oxygenate selectivity of 88.3% in the total oxygenates was obtained at 42.4% CO conversion, decidedly outperforming the previous Rh-based catalysts. This work provides a new route for design and preparation of highly efficient catalyst for ethanol production from syngas.

Von Amiden zu Carbenen: In einer Eintopfreaktion lassen sich Phosphonio‐substituierte Iminiumsalze einfach aus den entsprechenden Amiden erhalten. Ihre Deprotonierung mit anschließenden Substitutionsreaktionen liefert eine Vielzahl an instabilen und stabilen Aminocarbenen (siehe Schema).

The effects governing the rate of reductive elimination of dimethyl ether, acetonitrile, vinyl cyanide, and methyl ethanoate from palladium diphosphine complexes were studied by means of a density functional theory method. Energy barriers, computed as the difference in energy between the reactant and the corresponding transition state using H2P(CH2)2PH2 as model for diphosphine ligands, varied from 38 kcal mol-1 (dimethyl ether) to barrierless elimination of methyl ethanoate, in good agreement with experimental results. MO analysis reveals striking differences that are related to the donor/acceptor capabilities of the reacting moieties. For the elimination of acetonitrile, the bite angle effect on the reaction rate, observed by Moloy when different diphosphine ligands were used, was studied in depth. We considered (R2PXPR2)Pd(CH3)(CN) complexes for a number of different ligand backbones (X = (CH2) n , n = 1−4; X = cis-, trans-but-2-ene) which span a large bite angle range and for a number of different phosphine substituents (R = H, Me, Ph). With the use of QM/MM strategies, steric and electronic effects were separated and evaluated, and the results indicate that the rate enhancement is electronic in nature, steric effects being negligible. The analysis reveals that wide bite angle ligands destabilize the reactant and stabilize the transition state, thus accelerating the reaction.

The rate-determining step in the hydroformylation of 1-octene, catalysed by the rhodium-Xantphos catalyst system, was determined by using a combination of experimentally determined (1)H/(2)H and (12)C/(13)C kinetic isotope effects and a theoretical approach. From the rates of hydroformylation and deuterioformylation, a small (1)H/(2)H isotope effect of 1.2 was determined for the hydride moiety of the rhodium catalyst. (12)C/(13)C isotope effects of 1.012(1) and 1.012(3) for the alpha-carbon and beta-carbon atoms of 1-octene were determined, respectively. Both quantum mechanics/molecular mechanics (QM/MM) and full quantum mechanics calculations were carried out on the key catalytic steps, for "real-world" ligand systems, to clarify whether alkene coordination or hydride migration is the rate-determining step. Our calculations (21.4 kcal mol(-1)) quantitatively reproduce the experimental energy barrier for CO dissociation (20.1 kcal mol(-1)) starting at the (bisphosphane)RhH(CO)(2) resting state. The barrier for hydride migration lies 3.8 kcal mol(-1) higher than the barrier for CO dissociation (experimentally determined trend approximately 3 kcal mol(-1)). The computed (1)H/(2)H and (12)C/(13)C kinetic isotope effects corroborate the results of the energy analysis.