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)3P(O)(OSiMe3)2 ( L), (cis-Cl2Pt[Ph2P(CH2)3P(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 31P 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.