A variety of palladium on activated carbon catalysts differing in Pd dispersion, Pd distribution, Pd oxidation state, and water content were tested in Heck reactions of aryl bromides with olefins. The optimization of the catalyst (structure ± activity relationship) and reaction conditions (temperature, solvent, base, and Pd loading) allowed Pd/C catalysts with very high activity for Heck reactions of unactivated bromobenzene (turnover number (TON) % 18 000, turnover frequency (TOF) up to 9000, Pd concentrations down to 0.005 mol %) to be developed. High Pd dispersion, low degree of reduction, sufficient content of water, and uniform Pd impregnation are criteria for the most active system. The catalysts combine high activity and selectivity under ambient conditions (air and moisture), easy separation (filtration), and quantitative recovery of palladium. De-termination of Pd in solution after and during the reaction, and catalyst characterization before and after the reaction (transmission electron microscopy (TEM), X-ray diffraction (XRD)), indicate dissolution/reprecipitation of palladium during the reaction. The Pd concentration in solution is highest at the beginning of the reaction and is a minimum (< 1 ppm) at the end of the reaction. Palladium leaching correlates significantly with the reaction parameters.

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A specially optimized air-stable Pd on activated carbon catalyst is demonstrated to be a highly active (TON up to 36,000), selective and convenient heterogeneous catalyst for CC couplings of aryl halides in Heck, Suzuki, and Sonogashira reactions. The Pd/ C catalyst developed allows extremely low Pd concentrations (down to 0.0025 mol% for Heck coupling, 0.005 mol% for Suzuki coupling) and high conversions of aryl bromides within a few hours. Easy and complete Pd separation and recovery is possible.

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We have used a multi-technique approach to allow us to build a consistent picture of the carbons used for catalyst supports and suggest reasons for the differences between the supports. From the catalyst tests it is clear that the nature of the support has a major influence on the catalyst performance. In part, this is the result of the activation method, however, the hydrogen content of the support also influences the activity. SEM pictures show that the characteristic structures present in the starting material are preserved after carbonisation. The inelastic neutron scattering spectra show that this is also true at the atomic level, with carbons from different sources having different patterns of edge termination of the graphitic structures. That different patterns of edge termination are reflected in the INS spectrum in the out-of-plane C-H bending region around 880 cm À1 is supported by DFT calculations. XPS and SIMS measurements show that for all the carbons, oxygenated and non-aromatic structures are located at the surface of the materials and both decrease rapidly with depth. Comparison of a wood-derived activated carbon before and after impregnation with platinum showed changes that were consistent with reactions on the support during impregnation and reduction treatment in generating the final supported precious metal/carbon catalyst. In addition to redox activity in oxygenated sites enhanced sp 2 type disorder contributes to improved catalyst dispersion.

Two‐phase catalysts with sugar‐substituted ligands, such as glycoside–triarylphosphanes 1 a–c, reveal advantages over catalysts with the classical TPPTS ligands in Heck and Suzuki reactions. A simple and generally applicable synthesis has been developed for this new class of neutral, hydrophilic ligands. On account of thermoreversible solvation, the concentration of the two‐phase catalyst in the nonpolar medium increases with increasing temperature, as shown by the Nernst distribution coefficient determined for one of the new ligands at different temperatures.

The purpose of the present investigation was to utilize the inelastic incoherent neutron scattering (INS) technique to reveal changes at the surface of technical catalysts under the influence of hydrogen in gas/solid interactions and during chemical reactions in a liquid-phase process. The formation and the properties of supported palladium hydride and changes of the hydrogen-related surface chemistry of the corresponding activated carbon supports in 20% Pd/C catalysts after short-term and long-term hydrogen cycling at different hydrogen pressures and temperatures were studied. The spectra indicate that hydrogenation of the activated carbon support by hydrogen spillover occurs to, partly, give a material that strongly resembles a-C:H (amorphous hydrogenated carbon). Indications for different relaxation phenomena and long-range phase coherence inside of supported particles of palladium hydride compared to hydrogenated palladium black were obtained. A 5% Pd/C catalyst after use in C-C coupling reactions, the Heck reaction of bromobenzene and styrene to stilbenes, was also studied after subsequent solvent extraction. Evidence for a preferential adsorption and accumulation of cis-stilbene at the catalyst surface was obtained. INS allows identification of a certain isomer from a complex reaction mixture preferentially adsorbed at the surface of a finely divided industrial heterogeneous catalyst.

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