Highly Effective Supported Ionic Liquid-Phase (SILP) Catalysts: Characterization and Application to the Hydrosilylation Reaction

Abstract

Organosilicon compounds, because of their unique properties, are widely used in a variety of organic processes, and thus the constant improvement of current methods is still needed. We present slurry-phase hydrosilylation reactions using novel supported ionic liquid-phase (SILP) catalysts containing rhodium complexes immobilized in four phosphonium ionic liquids (ILs) on silica support. The obtained new SILP catalysts were analyzed by infrared technique, low-temperature nitrogen physisorption at 77 K, and scanning electronic microscopy with energy-dispersive X-ray spectroscopy to provide structural information on these materials. Moreover, the catalytic activity in hydrosilylation reactions was evaluated and compared with the catalytic activity of rhodium catalysts dissolved in the same ILs when using a biphasic reaction system (IL/catalyst as one phase and mixture of substrates as a second phase). The rhodium-based SILP catalysts proved to be much more efficient than when used in a biphasic system composed of a similar catalyst and reactants. Furthermore, as a result of the presented study, we have identified a highly active SILP catalyst ([{Rh(μ-OSiMe₃)(cod)}₂]/[P₆₆₆₁₄][NTf₂] supported on silica) that allowed us to decrease the amount of catalyst used in the reaction by 1000 times in comparison with the amount of catalyst required while performing reaction using the biphasic catalytic system. The proposed method of utilization of SILP materials can become a significant step in reducing expensive organometallic catalyst consumption in organic chemistry and, when applied more broadly, lead to significant cost savings, eventually making the production of many organic molecules more sustainable.