Exchange for the better: Mesoporous sodalite and NaA zeolite exchanged with Pd(2+) exhibit remarkably high activity and reusability in C-C coupling reactions under aerobic atmosphere. It is proposed that the catalytic reactions are mediated by a molecular Pd(0) species generated in situ within the pores (see picture), which is oxidized back to Pd(2+) by O(2), preventing the formation of catalytically inactive Pd(0) agglomerates.

Mesopore walls of hierarchically meso-/microporous zeolites (MFI, BEA and LTA) are covered with silanol groups, so that the zeolites can be functionalized with various organic groups via silylation; the organic-functionalized hierarchical zeolites exhibit hydrothermal stability and reusability in catalytic applications, as compared with organic-functionalized mesoporous silica.

A mesoporous LTA zeolite (MP-LTA)-supported palladium catalyst was developed for the highly efficient Suzuki-Miyaura reaction of aryl and heteroA C H T U N G T R E N N U N G aryl chlorides. The couplings of various aryl chlorides with arylboronic acids in aqueous ethanol were efficiently achieved in the presence of 1.0 mol% of the catalyst. Furthermore, the scope of this catalyst was extended to the coupling of heteroaryl chlorides. Regardless of the substituents, all of the coupling reactions were very clean and highly efficient under mild heating. It shows that our catalyst is one of the most powerful heterogeneous catalysts for the coupling of a wide range of aryl and heteroaryl chlorides. The catalyst could be repetitively used at least 10 times without a significant loss of its catalytic activity. Compared to mesoporous SBA-15 and MCM-41 materials, the MP-LTA support proved to be very stable and robust to prevent degradation upon reuse.

Wechsel zum Besseren: Mesoporöse Sodalit‐ und NaA‐Zeolithe, die durch Ionenaustausch mit Pd2+ beladen wurden, zeigen bemerkenswerte Aktivitäten in C‐C‐Kupplungen unter aeroben Bedingungen und können mehrfach verwendet werden. Die Katalyseschritte werden vermutlich durch in situ gebildete Pd0‐Spezies vermittelt (siehe Bild), die durch O2 zu Pd2+ rückoxidiert werden, was die Bildung katalytisch inaktiver Pd0‐Agglomerate verhindert.magnified image

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