PS-PPh2 tethered Pt single atoms promoted by SnCl2 as highly efficient and regio-selective catalysts for the hydroformylation of higher α-alkenes

Abstract

Rh-P complexes have been widely used as catalysts for hydroformylation reactions. The extremely high price of Rh and its scarce reserves have prompted the exploration of the alternatives. In this study, we reported that Pt/PS-PPh₂ single-atom catalysts promoted by SnCl₂ were highly efficient and selective for the hydroformylation of higher α-alkenes. A broad scope of substrates (i.e., C₆–C₁₂) were smoothly converted to the corresponding linear aldehydes with high yields under reaction conditions of 90–120 °C and 4–6 MPa syngas. The turnover frequency (TOF) was comparable to homogeneous Pt-Sn catalysts, and the linear/branched ratio reached as high as > 20. In addition, the catalyst could be reused with the extra addition of SnCl₂. The promotional role of SnCl₂ was elucidated by quasi-in situ X-ray adsorption fine structure, Fourier transform infrared, and Mössbauer spectroscopy. It was discovered that SnCl₂ was transformed into Sn(dioxane)Cl₃⁻ species coordinated to Pt as a moderately electron-donating ligand, which, together with the phosphine group, stabilized mononuclear Pt (I) species against reduction and aggregation.