Self‐assembly aryl cyclopalladated imine film supported on the silicon surface—Fabrication, formation of active PdPd/PdO sites, and catalytic properties for Sonogashira cross‐coupling reaction

Abstract

Tailoring the structure and arrangement of the organometallic catalyst are essential for the fundamental investigating and applications, and the impacting challenges, such as the size, active species distribution, and composition, as well as the orientation of catalyst, are critical for determining their activities and efficiencies. Herein, a series of aryl cyclopalladated catalysts containing different alkane chains were synthesized, and their self‐assembly films covalent binding to the silicon surface were fabricated and characterized with water drop contact angle, Raman, atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The catalytic performances of these catalytic films were explored using Sonogashira cross‐coupling reaction as a template. One of these catalytic films exhibited a higher catalytic activity with a TON value of up to 68,333 h−1, which was 20 times higher than that of homogeneous catalyst due to the ordered arrangement of this catalyst on the silicon surface, and could be reused at least seven times. The catalytic mechanism was heterogeneous catalysis occurred at interface confirmed by hot filtration tests, poisoning tests, and ReactIR. The real active site was PdPd/PdO, and the synergistic effect between Pd and PdO in the active sites (PdPd/PdO) made the key initial oxidation step easily proceed, improving its catalytic activity. The loss of active sites and residues absorbed on the surface of catalytic film were the main reason for deactivation.