{Ti6}/{Ti10} Wheel Cluster Substituted Silicotungstate Aggregates.

Two novel Ti-oxo wheel cluster substituted silicotungstates (STs) [H2N(CH3)2]9H9[Ti6O6(SiW10O37)3]·11H2O (1) and [H2N(CH3)2]16H10[Ti10O11(SiW10O37)2(SiW9O35)2]·14H2O (2) have been made by hydrothermal reactions. The polyoxoanion of 1 is a ring-shaped trimer where a Ti6O6 ({Ti6}) wheel cluster is encapsulated by three divacant [SiW10O37]10- (SiW10O37) fragments. However, 2 is built by two divacant SiW10O37 units and two rare trivacant [SiW9O35]12- (SiW9O35) fragments and further installs an unprecedented Ti10O11 ({Ti10}) double-wheel cluster. To the best of our knowledge, 2 is rare in POM chemistry. Studies on the catalytic oxidation properties reveal that 1 exhibits high catalytic activity toward the oxidation of various sulfides using H2O2 as an oxidant. Furthermore, 1 can be facilely recycled and reused for at least five cycles without obvious loss of catalytic activity.