Titanium tetra-isopropoxide reacts with the silanol groups of MCM41 calcined at two different temperatures, 550 and 750°C, to form well-defined surface organometallic species. For MCM41 calcined at 550°C, the amount of available silanol allows mainly the formation of the bipodal titanium complex, (≡SiO) 2 Ti(O i Pr) 2 , while calcination at 750°C leads to the formation of the monopodal titanium complex ≡SiO-Ti(O i Pr) 3 . Ti-MCM41 (750) was found to be more active and selective in the oxidation of sulfides, compared to Ti-MCM41 (550), and this can be attributed to the development of a large amount of tetrahedral isolated titanium (IV) which seems to be the active site in this reaction. In the asymmetric oxidation of sulfide by H 2 O 2 , Ti-MCM41 (750) was found also more reactive than Ti-MCM41(550), since it develops the singly bonded titanium species, ≡SiO-Ti(O i Pr) 3, which appears to be the chiral active site in this reaction.