Use of titanium-containing silica catalysts prepared by rapid and straightforward method in selective oxidations

A series of titanium-containing silica catalysts (Ti4/SiO2) with small oligomeric Ti centres is obtained by impregnation of the air-stable and water-soluble tetranuclear Ti complex (NH4)8[Ti4(C6H4O7)4(O2)4]·8H2O onto commercial non-ordered mesoporous silica supports. Catalyst preparation is performed under very mild conditions, with no controlled atmosphere, following a simple, cheap, safe and sustainable methodology. Ti4/SiO2 catalysts can be used in the presence of TBHP or aqueous hydrogen peroxide and were tested in the selective oxidation of limonene, cyclohexene, transstilbene and 2,3,6-trimethylphenol. These catalysts showed performances fully comparable to (or even better than) those obtained with titanium-silicate materials prepared via conventional post-synthesis grafting approaches from organometallic precursors.