Tunable latency of hydrosilylation catalyst by ligand density on nanoparticle supports.

The tethering of inorganic particle surfaces with organic ligands serves as a common technique for heterogenizing organometallic catalysts. We describe how the coordination of molecular platinum to high density norbornene-functionalized silica nanoparticles results in an unexpected latency of the catalytic activity (2% conversion after 60 min) in hydrosilylation reactions when compared to an identical reaction in which the norbornene is not tethered (97% conversion after 60 min). 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 the density of the ligand on the inorganic particle surface, the chemical structure of the norbornene, and the topology of the silica nanoparticles. We also establish the benefit of this latency effect for the triggered curing of silicone elastomers. Overall, our work establishes the non-innocent role of inorganic supports when functionalized with organometallic complexes.