Nanospheres can be formed by combining 24 bispyridinyl building blocks with ap alladium or platinum precursor. Theses pheresc an be functionalized on the inside with ag old(I) chloride complex leading to ah igh local concentration of gold(I) complexes. Theh igh local concentration makes the neutral gold species an active catalyst. Furthermore,t he platinum-gold spheresc an be post-modified with as ilver(I) salt to form cationic gold(I) catalysts.T he platinum assemblies are demonstratedt ob es table in the presence of various substrates and as aresultseveral cyclization reactions have been carried out using these new spheres as catalysts.H igher conversions in a[ 4 + +2] cycloaddition are observed for the sphere catalyst comparedt ot he mono-nuclear analogues. Also the cyclization of 1,6-enynes can be facilitated by the confined gold catalyst and high activity is observed in the activation of allenes.F or the lactonization of alkynoic acids,adifferent selectivity is observed comparedt oastandard gold(I) complex, demonstrating that the high local concentration due to ac onfined space can induce other selectivity in catalysis.
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