Cyclopalladated ferrocenylimine self-assembly films for Suzuki coupling reaction

The monolayer and LB films of cyclopalladated ferrocenylimine 1 were prepared at different surface pressure and applied for Suzuki–Miyaura reactions in the heterogeneous catalytic system. Morphology studies of monolayer were investigated by atomic force microscope (AFM), which showed that the surface morphologies of the LB films were significantly different at different surface pressure. LB films of cyclopalladated ferrocenylimine 1 prepared at surface pressure of 22 mN/m showed higher catalytic efficiencies compared with that at 14, 18, 26, 30 mN/m. These results demonstrated the catalytic efficiency was related to the molecular arrangement of the catalysts. The structure changes of cyclopalladated ferrocenylimine 1 LB films by low-angle X-ray diffraction (LAXD) as well as the film surface morphological changes by AFM in catalytic process were also investigated, which indicated that the substrate and base were contacting with the catalyst to cover the catalyst film surface at the beginning of catalytic process. The whole catalytic process included constantly contacting and covering the surface of the catalyst to generate Pd intermediates that could be transferred into the product, which were further identified by the X-ray photoelectron emission microscopy (XPS) analysis.

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► Cyclopalladated ferrocenylimine 1 LB films prepared at different surface pressure.
► Characteristic studies showed different molecular orientations in LB films.
► Suzuki–Miyaura reactions catalyzed by LB films had been studied.
► The catalytic efficiency of LB films was related to the molecular arrangement.
► Pd intermediate generated at beginning is the key step in films catalytic process.