Self-assembly Palladacycle Thiophene Imine Monolayer—Investigating on Catalytic Activity and Mechanism for Coupling Reaction

Abstract

An ordered cyclopallated thiophene imine self-assembly monolayer(Si@Pd3TI) was designed and fabricated. It was characterized by water contact angle(WCA), ultraviolet-visible spectroscopy(UV), cyclic voltammetry(CV), infrared(IR) spectrum, atomic force microscopy(AFM) and X-ray photoelectron spectroscopy(XPS). Its catalytic performance for Suzuki coupling reaction and catalytic mechanism were systematic investigated. Si@Pd3TI was validated as a heterogeneous catalyst identified by poisoning tests, hot filtration test and three-phase test. The heterogeneous catalytic mechanism was investigated by WCA, UV, Raman spectrum(RS), AFM, XPS and density functional theory(DFT). The catalytic mechanism proceeded via surface-catalysis process, on which the Pd(II)/Pd(I)/Pd(0) synergistic active center acted likely as “multimetallic cluster”. It played a great role for catalyzing coupling reaction, in which the real active species was Pd(I).