Radial distribution of heterogenized hydroformylation Rh complexes in phosphinated polystyrene beads

Abstract

AbstractRhodium(I) complexes anchored to 2% divinyl benzene cross‐linked phosphinated polystyrene have been prepared with chloride and pentafluorophenylthiolate ligands. The cross‐sectional distribution of the elements involved in the active complex has been examined by SEM‐EDX, and the surface composition by XPS. The combined use of both techniques revealed that Rh(I) complexes prepared from a chloride precursor form a weak bond with the phosphine groups of polystyrene, while this bond is stronger when the complex is prepared from a pentafluorophenylthiolate precursor. Owing to these chemical differences, the catalytic behaviour for hept‐1‐ene hydroformylation is quite different. While the life of a catalyst is only four reaction cycles in the former case, it is extended to more than eleven reaction cycles in the latter. In all cases, a well‐defined P (as phosphine) profile was observed, which decreased from the periphery to the centre of the beads. Such a profile was almost unaffected by the pretreatments or by the operative conditions; however, an important surface reorganization was observed just at the end of the catalyst's life. The profiles of other elements of the active component, namely Rh and Cl (or S), followed, in general, similar trends in fresh preparations but decreased markedly, especially in the ex‐chloride preparations, with the number of extraction– washing pretreatments and the number of cycles in the reaction.