We report on a site-isolated model for Ti(IV) by reacting [Ti( i PrO) 4 ] with the silanolfunctionalized polyoxotungstates [XW 9 O 34-x ( t BuSiOH) 3 ] 3-(X= P, x=0, 1; X= Sb, x=1, 2) in tetrahydrofuran. The resulting titanium(IV) complexes [XW 9 O 34-x ( t BuSiO) 3 Ti(O i Pr)] 3-(X= P, 3; X= Sb, 4) were obtained in monomeric forms both in solution and in the solid state, as proved by diffusion NMR experiments and by X-ray crystallographic analysis. Anions 3 and 4 represent