We report the N-heterocyclic carbene (NHC)-induced activation of an otherwise unreactive Pd/AlO catalyst. Surface analysis techniques demonstrate the NHC being coordinated to the palladium particles and affecting their electronic properties. Ab initio calculations provide further insight into the electronic effect of the coordination with the NHC injecting electron density into the metal nanocluster thus lowering the barrier for bromobenzene activation. By this NHC modification, the catalyst could be successfully applied in the Buchwald-Hartwig amination of aryl chlorides, bromides, and iodides. Various heterogeneity tests could additionally show that the reaction proceeds via a heterogeneous active species.
Ru nanoparticle catalysts were prepared from Ru12-metalloporphyrin complex precursors containing 3d transition-metal atoms attached to SiO2 surfaces. The single 3d metal atoms at the central position of the Ru12-metalloporphyrin complex precursors exerted a significant influence on the structures and hydrogenation performance of the Ru nanoparticles on the SiO2 surfaces. The Ru12-Cu-porphyrin complex afforded positively charged Ru nanoparticles, which would provide high activity toward aromatic hydrogenation.
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