Solvent‐Polarity‐Induced Assembly of Calixarene‐Capped Titanium‐Oxo Clusters with Catalytic Activity in the Oxygenation of Sulfides

Abstract

AbstractFour calixarene‐coordinated titanium‐oxo clusters, namely, [Ti4(C6A)2(μ3‐O)2(DMF)2] (CIAC‐258), [Ti8(H3C6A)4(C6H5PO3)8(μ2‐O)4]4− (CIAC‐259), [Ti6(TC4A)3(μ2‐O)3 (OiPr)6] (CIAC‐260) and [Ti6(H2TC4A)4(C6H5PO3)4(μ2‐O)5(DMF)2]2− (CIAC‐261) were obtained, which feature sandwich‐like, windmill‐like, triangular, and tetrahedral structures, respectively. The polarity of the solvent determines the involvement of the auxiliary ligand phenylphosphonic acid in the formation of the products and their structures. Compounds CIAC‐258 and CIAC‐261 exhibit good catalytic performance in the selective oxidation of sulfides to sulfoxides with H2O2 as the oxidant, which can be attributed to the Ti active sites coordinated by exchangeable DMF molecules. Moreover, density functional theory (DFT) calculations revealed that the Ti‐hydroperoxo species formed by the interaction of the Ti active site in CIAC‐258 or CIAC‐261 and H2O2 is the most likely catalytic active component during the catalytic sulfoxidation process.