Tunable Latency of Hydrosilylation Catalyst by Ligand Density on Nanoparticle Supports

Abstract

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 noninnocent role of inorganic supports when functionalized with organometallic complexes.

Encapsulated Transition Metal Catalysts Enable Long-term Stability in Frontal Polymerization Resins

“…Alternatively, we propose that latency in FROMP resins can be achieved via a localized separation between monomer and active catalyst that can be removed upon exposure to an external stimulusa technique ubiquitous in biological systems. , An established way to delay contact between reactive pairs is the encapsulation of molecular cargo in the form of polymer microparticles (PMPs). This well-studied method has been applied to the controlled release of drug molecules, , catalyst species, − and polymerization initiators. − Pojman et al demonstrated that microencapsulation of organic peroxide initiators increases the storage life of free-radical acrylate FP . Extended storage times (>1 day) resulted in significant decreases in the mechanical properties of the polymer products and SP still occurred within a two month period.…”