It's been almost a decade since first report on successful catalysis by supported gold cluster came out. Since then, it has been a hot area of research and scientist are working hard to explore new strategies for catalysis using similar systems.
Recently, an interesting report published in Chem Commun. by Tsukuda and his coworkers wh talks about efficient and highly selective epoxidation of styrene by HAP (hydroxyapatite: Ca10(PO4)6(OH)2 ) supported Au25 cluster using TBHP as oxidant. Synthesis of supported Au25 on HAP involves deposition of Au25 clusters protected by 18 glutathionate (GS) ligands, Au25(SG)18, on an HAP support and then calcine the composite to remove the GS ligands.It is expected that Au25(SG)18 get adsorbed on HAP by electrostatic interaction between Ca2+/PO43− moieties and the GS ligands, and that HAP could stabilize bare Au25 clusters against sintering due to strong interaction with the PO43– moiety.
High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) is used to confirm the size and distribution of resulting Au clusters. Further, TG analysis is used to confirm the loss of thiol group from the surface after calcination at 300 degree C in vaccum.
Oxidation of styrene in toluene at 80 °C using anhydrous TBHP as an oxidant yielded styrene oxide as a major product in every case ( slectivity almost 100%) when Au25 support on HAP system is used as catalyst. Catayst also show excellent reusability without any significant loss in either the catalytic activity or the selectivity.
Oxidation of styrene in toluene at 80 °C using anhydrous TBHP as an oxidant yielded styrene oxide as a major product in every case ( slectivity almost 100%) when Au25 support on HAP system is used as catalyst. Catayst also show excellent reusability without any significant loss in either the catalytic activity or the selectivity.
Reference : Chem. Commun., 2010, 46, 550 - 552
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