Tunable Latency of Hydrosilylation Catalyst by Ligand Density on Nanoparticle Supports.

Functionalizing inorganic particles with organic ligands is a common technique for heterogenizing organometallic catalysts. We describe how coordinating molecular platinum to silica nanoparticles functionalized with a high density of norbornene ligands causes unexpected latency of the catalytic activity in hydrosilylation reactions when compared to an identical reaction in which the norbornene is not tethered (2 % vs 97 % conversion in 1 h). Performing the hydrosilylation at elevated temperature (70 °C) suppresses this activity delay, suggesting the usefulness of this technique towards temperature-triggered catalysis. We demonstrate that this latency is related to ligand density on the particle surface, chemical structure of the norbornene, and silica nanoparticle topology. We also establish the benefit of this latency for triggered curing of silicone elastomers. Overall, our work establishes the non-innocent role of inorganic supports when functionalized with organometallic complexes.