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.