Hyperbranched Polyester Polycarbamoyl Phosphonate Doped with Palladium(II) Ions for Catalytic Hydrogenation of α-Methylstyrene

A second-generation hyperbranched polyester with the terminal carbamoyl phosphonate groups has been synthesized. The structure of the resulting polyester has been studied by IR, ¹H NMR, ³¹P NMR, and electron spectroscopy. It has been found that 25% of the terminal OH groups of polyester polyol were subjected to functionalization. Using the TGA method, the thermal stability temperature of the resulting polyester was evaluated to be 138°C. We have synthesized a complex of the resulting polyester with the Pd(II) ions, and the complex structure has been studied by IR and electron spectroscopy. The composition of the ligand–Pd(II) complex has been evaluated to be 1 : 6. We have found by the TGA method that this complex is thermally stable up to 207°C. The temperature of reduction of the Pd(II) ions by molecular hydrogen to Pd(0) has been assessed as –20.6°C. Electron microscopy has been used to demonstrate the spherical morphology of hyperbranched polyester polycarbamoyl phosphonate with Pd(0) atoms, with the predominant fraction being 1.5 μm. It has been shown that the use of hyperbranched polyester polycarbamoyl phosphonate as a catalyst provides the activation energy of 55.8 kJ/mol for hydrogenation of α-methylstyrene to cumene with the effective rate constant of 1.950×10^–2 L/(g_cat s) at 45°C and atmospheric pressure. The results indicate the prospects of using hyperbranched polyester polycarbamoyl phosphonate as a matrix to obtain catalysts for the hydrogenation of unsaturated compounds.