Immobilization of platinum(II) and palladium(II) complexes on metal oxides by sol-gel processing and surface modification using bifunctional phosphine-phosphonate esters

The bifunctional phosphine-phosphonate ester derivatives Ph2P(CH2)(3)P(O)(OSiMe3)(2) (L), (cis-Cl2Pt[Ph2P(CH2)(3)P(O)(OSiMe3)(2)](2) (1), trans-Cl2Pd[Ph2P(C6H4)P(O)(OSiMe3)(2)](2) (2) and trans-Cl2Pd[Ph2P(C6H4)P(O)(OEt)(2)](2) (3) were used to immobilize platinum(II) and palladium(II) complexes on metal oxide supports by three different routes: sol-gel incorporation of L in TiO2 or ZrO2 matrices followed by complexation with PtCl2(PhCN)(2), direct sol-gel immobilization of 1 and 2, surface modification of TiO2 nanoparticles with 2 and 3. The hybrid solids were characterized by solid-state P-31 MAS NMR spectroscopy, surface area measurements and chemical analysis; the advantages and disadvantages of the different routes were discussed. This study demonstrates that phosphonic esters can provide a valuable alternative to phosphonic acids for the preparation of functional organic-inorganic hybrids based on metal oxides.