Titanium silsesquioxane, preparation

The fulvene route was also successfully employed in the preparation of a compound, which can be regarded as one of the most advanced molecular models for a catalytically active titanium center on a silica surface. When Cp Ti(C5Me4CH2) was reacted with the monosilylated silsesquioxane precursor 12 in refluxing toluene a color change from deep purple to amber was observed. Crystallization afforded a bright-yellow material, which was subsequently shown to be the novel mo o(pentamethyleyclopentadienyl) titanium(IV) silsesquioxane complex 126 (69% yield). Its formation is illustrated schematically in Scheme 42. 

Smet, R, Riondato, J., Pauwels, T., Moens, L. and Verdonck, L. Preparation and characterization of a titanium(IV) silsesquioxane epoxidation catalyst anchored into mesoporous MCM-41, Inorg. Chem. Commun., 2000, 3, 557-562. 

In yet another approach, titanium(IV) silsesquioxanes were shown to be excellent homogeneous catalysts for epoxidations with TBHP [55]. A heterogeneous variant was prepared by adsorbing the Ti(IV) silsesquioxane in the pores of MCM-41 that had been silylated with Ph2SiCl2 to passivate the external surface. The resulting material was reported to be a stable, recyclable catalyst for epoxidations with TBHP [56]. 

In yet another novel approach titanium(IV) silsesquioxanes (see Figure 2 for structure) were prepared and shown to be excellent homogeneous catalysts for... 

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