Formation of a covalent bond between a polyoxometalate and silica covered by SiH moieties

Dehydroxylated silica was modified by grafting reaction of SiHMe ₂ groups. The resulting material was fully characterized by various methods including infrared and one- and two-dimensional solid-state NMR. This material can further react with dehydrated polyoxometalates (POMs), leading to the formation of a covalent POM-silica bond. In the case of H ₄PVMo₁₁O₄₀, hydrogen released during the grafting reaction reduces the POM. This leads to the formation of two surface species, which can be reoxidized in presence of oxygen. In the case of H ₃PW₁₂O₄₀, no reduction is observed. In both cases, ²⁹Si solid-state NMR shows that the POM-silica bond is covalent, contrary to what was observed in homogeneous conditions.