Zero-oxidation state precursor assisted fabrication of highly dispersed and stable Pt catalyst for chemoselective hydrogenation of α,β-unsaturated aldehydes

The chemoselective hydrogenation of α,β-unsaturated aldehydes is a key strategy for the synthesis of fine chemicals. Herein, we developed an efficient method of depositing Pt particles on FeO_x/SBA-15. This strategy is dependent on using a platinum-divinyltetramethyldisiloxane complex (Pt⁰-DVTMS) as the precursor, which we demonstrate can be removed through a H₂-treatment under mild conditions. This, in turn, allowed for the synthesis of catalysts with well dispersed Pt particles. The presence of FeO_x species also aided Pt dispersion; when coated onto SBA-15, FeO_x strongly interacted with dissociated Pt species, inhibiting both Pt aggregation and metal leaching. Using cinnamaldehyde as a model α,β-unsaturated aldehyde, it was demonstrated that this catalyst was highly selective towards the unsaturated alcohol and no obvious loss in activity was observed over five recycles. This catalyst was determined to be significantly more effective than an analogous catalyst prepared using chloroplatinic acid as a precursor, evidencing the importance of using the Pt⁰-DVTMS precursor. We corroborate the excellent catalytic performance to highly dispersed Pt-species, whereby Pt⁰ and Pt²⁺ play a critical role in activating H₂ and the C=O bond. This research demonstrates that the Pt precursor can have a significant impact on the physicochemical properties and thus, the performance of the final catalyst. It also evidences how metal support interactions can dramatically influence selectivity in such hydrogenation reactions. This novel catalyst preparation protocol, using a DVTMS ligand for Pt impregnation, offers a facile approach to the design of multi-component heterogeneous catalysts.