Highly efficient hydrosilylation catalysts based on chloroplatinate “ionic liquids”

The reaction between ionic liquid [Cat]+Cl− (where Cat stands for 1-butyl-3-methylimidazolium, 1-butyl-2,3-dimethylimidazolium or 1-butyl-4-methylpyridinium) and the metal precursor ([PtCl2(cod)], PtCl4, K2[PtCl4] or K2[PtCl6]) yielded two groups of derivatives: [Cat]+[PtCl4]− and [Cat]+[PtCl6]−, which formally are counted among halometallate ionic liquids, however, due to their high melting points they should be classified into anionic platinum complexes rather than into ionic liquids. All the derivatives were isolated and characterized spectroscopically (NMR, ESI-MS) and crystallographic structures were determined for three derivatives: ([BMPy]2[PtCl4], [BMIM]2[PtCl6] and [BMMIM]2[PtCl6]. Moreover, their melting points were measured and thermal stability was assessed. The above derivatives were employed as catalysts for hydrosilylation of olefins with diverse properties. All the studied catalysts showed high activity and their insolubility in the reaction medium made easy their isolation and multiple use in subsequent catalytic runs. The most effective catalysts did not lose their activity even after ten runs, thereby they make a very good alternative to commonly used homogeneous catalysts. Their simple synthesis and stability make them interesting both for economic and ecological reasons.