Small Titanium Oxo Clusters: Primary Structures of Titanium(IV) in Water

For sol–gel synthesis of titanium oxide, the titanium­(IV) precursors are dissolved in water to form clear solutions. However, the solution status of titanium­(IV) remains unclear. Herein three new and rare types of titanium oxo clusters are isolated from aqueous solutions of TiOSO<sub>4</sub> and TiCl<sub>4</sub> without using organic ligands. Our results indicate that titanium­(IV) is readily hydrolyzed into oxo oligomers even in highly acidic solutions. The present clusters provide precise structural information for future characterization of the solution species and structural evolution of titanium­(IV) in water and, meanwhile, are new molecular materials for photocatalysis.