Highly active and selective catalysts for olefin hydrosilylation reactions using metalloporphyrins intercalated in natural clays

Abstract

Tetra(4-pyridyl)porphyrinato-manganese(III) (MnTPyP⁺) ions intercalated inside nano- and micro-size natural clay powders effectively catalyzed the hydrosilylation reaction of 1-octene and tri(ethoxy)silane under mild conditions. The results showed that the homogeneous MnTPyP⁺ ions catalyzed the reaction where both branched and linear products were observed. Intercalation significantly enhanced both catalyst activity and selectivity. Production of the linear tri(ethoxy)silyl-1-octane as sole product was confirmed by FT-IR and NMR spectra, in the case of the intercalated catalyst. The activity enhancement was more pronounced in the case of the nano-particle supported catalyst system, with turnover frequency (TF) values up to 1200 min⁻¹ and 85% conversion observed in less than 20 min. The intercalated catalyst systems were easy to recover and were reused three times, while retaining up to 80% of their original activity. Effects of different reaction parameters on the initial reaction rate, such as clay particle size, solvent polarity, reactant concentration, catalyst loading and temperature, were investigated. A new plausible mechanism, with evidence and justifications, is proposed.