XPS Study of the Synthesis of Single-Site Catalysts Based on Ir(I) and Rh(I) Complexes Immobilized on the SiO2 Surface Using a P-Containing Linker

Samples of model single-site catalysts based on iridium and rhodium were synthesized by immobilizing the complexes [Ir(COD)(IMes)Cl] and [Rh(COD)(IMes)Cl] (where COD is 1,5-cyclooctadiene and IMes is 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) on silica, the surface of which was modified with a linker containing a diphenylphosphine group (Ph₂P). The supports were silicon plates with a flat surface coated with a layer of natural oxide 1–3 nm thick (Si–SiO₂(nat)) or with a specially grown SiO₂ film (∼300 nm) (Si–SiO₂(ox)). The states of chemical elements in the modified silicon plates and samples of model catalysts were determined by XPS. Based on the results obtained, the nature of the coordination of the immobilized complexes was assumed. Samples of the catalysts were tested in the reaction of gas-phase hydrogenation of propene with parahydrogen.