Fabrication and Catalytic Property of an Ordered Terpyridine Pd(II)/Ni(II) Catalytic Monolayer for Suzuki Coupling Reactions

Abstract

Fabrication, arrangement, and controllable composition of ordered organometallic films are critical for designing a highly active catalyst and investigating the catalytic mechanism. In this paper, an organometallic terpyridine Pd(II)/Ni(II) monolayer linked on the silicon substrate surface (denoted as <strong>Si-Tpy-Pd<sub>1</sub>/Ni<sub>1</sub></strong>) was prepared and characterized using water contact angle, ultraviolet spectra, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron microscopy. <strong>Si-Tpy-Pd<sub>1</sub>/Ni<sub>1</sub></strong> exhibited high catalytic activity, substrate applicability, and reusability after 5 runs. During recycling, the deactivation was induced by the aggregation of active Pd/Ni nanoparticles. The catalytic mechanism was heterogeneous and occurred on the <strong>Si-Tpy-Pd<sub>1</sub>/Ni<sub>1</sub></strong> monolayer surface; the mechanism was confirmed using hot filtrate, poison test, and a three-phase experiment. The real active center was Pd<sup>δ</sup><sup>–</sup>/Ni<sup>δ+</sup> and was formed in situ on the organometallic monolayer surface, which acted as a precursor with a synergistic effect between Pd and Ni. The electron density of Pd became more negative because of electron transfer from Ni to Pd, which facilitated the oxidative addition reaction.

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

“…Among many supports, [23][24][25][26] silicon wafers have drawn growing interest due to their regular surface and chemical stability, providing the active site on the regular surface and the ordered chemical organometallic films as an investigating platform. [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] Self-assembly method (SAM) provides a customized design, controllable arrangement, easy reproduce and stable monolayer, and the surface structure of the catalyst film on the supports is also an important factor affecting the activity, 46 which can be endowed through modifying the surface of catalyst by using SAM. The regular surface can be used as an ideal platform to elucidating the catalytic mechanism, [47][48][49][50][51][52] on which the structure, the real active center and the change of active sites can be easily detected and elucidated.…”

“…How to design the heterogeneous catalyst easily obtained with high activity is one of the most challenges. Among many supports, 23–26 silicon wafers have drawn growing interest due to their regular surface and chemical stability, providing the active site on the regular surface and the ordered chemical organometallic films as an investigating platform 27–45 …”