Tripodal tetrahedral titanium coordination in the silica-grafted titania epoxidation catalysts: is not it only a myth? Selective formation of [Cy7Si7O12Ti]2(mu-OR)2(mu-ROH) cores on thermal "dissociation" of alkoxytitanasilsesquioxanes.

The molecular structures of the species crystallizing from solutions of alkoxytitanasilsesquioxanes in hydrocarbons upon reflux confirm the partial release of solvating alcohol. They feature, however, distinctly the formation of a dinuclear core with preserved hexacoordination for the metal atoms. The active titanium centers in the silica-titania epoxidation catalysts, lacking the sterically demanding ligands, are thus quite probably also hexacoordinated.