Preparation, characterization and evaluation of a series of heterogeneous platinum catalysts immobilized on magnetic silica with different acid ligands

Platinum was immobilized on magnetic silica gel by means of boronic, nitric, carboxylic or sulfuric acid ligands to give four heterogeneous Pt nano-catalysts, designated as Fe 3 O 4 @SiO 2 -BA@Pt, Fe 3 O 4 @SiO 2 -NA@Pt, Fe 3 O 4 @SiO 2 -CA@Pt and Fe 3 O 4 @SiO 2 -SA@Pt, respectively. Particles of these mono-dispersible Pt catalysts were 10–20 nm in size and could be separated for recycling by means of a magnet. Fe 3 O 4 @SiO 2 -BA@Pt (0.174 mmol/g Pt) showed the best catalytic activity and selectivity, which were better than Speier’s catalyst. Its turnover numbers were up to 1.7 × 10 6 and 1.1 × 10 6 for hydrosilylation of 1-hexene or styrene, respectively. This material could also catalyze the hydrosilylation of a broad range of alkenes and alkynes as substrates and methyldichlorosilane or triethoxysilane as silanes. Similar yields of 1-hexyl-methyldichlorosilane at the first and eighth runs (96.5% and 95.2%, respectively), together with a final Pt content of 0.171 mmol/g indicated the outstanding stability of Fe 3 O 4 @SiO 2 -BA@Pt under the catalytic reaction conditions.