Abdulelah Taher Ali Mohammed

Shanghai Normal University, China

Hollow–Shell–Structured Mesoporous Silica-Supported Palladium Catalyst for An Efficient Suzuki–Miyaura Cross-Coupling Reaction

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Biography

Abstract

The construction of high stability heterogeneous catalyst for privileged common catalysts is a benefit for the reuse and separation catalyst from reactants. Herein, a palladium diphenylphosphine-base Hollow-shell-structured mesoporous catalyst (HS@PdPPh2@MSN) is prepared by the immobilization of bis[(diphenylphosphino)ethyltriethoxysilane]palladium acetate onto the inner wall of mesoporous organicsilicane Hollow-shell whose surface be protected by -Si(Me)3 group. In detail Hollow-shell-structured (PPh2)2Pd(OAc)2-functionalized mesoporous silica nanoparticles, abbreviated as HS@PdPPh2@MSN , were synthesized through a simple post-grafting-complexation three-step procedure, as shown in Scheme 1. The first step was the co-condensation of tetraethoxysilane (TEOS) and 1,2-bis(triethoxysilyl)ethane, followed by the modification of hexamethyldisilazane (HMDS) leading to silylated core-shell-structured nanoparticles Me@SiO2@NPs. The second step was the post grafting of diphenyl(2-(triethoxysilyl)ethyl)phosphane within the inner surface of the silylated Me@HS@MSN (1), which was obtained by an etching process in toluene for 12 h under refluxing condition. The third step was the direct complexation of the immobilized diphenyl(2-(triethoxysilyl)ethyl)phosphane with Pd(OAc)2 in the cavity of the hollow-shell-structured mesoporous silica and producing of the coarse catalyst 3, which was subjected to a Soxhlet extraction to remove the unreactive materials providing its pure form as a gray powder. Structural analyses and characterizations of the heterogeneous catalyst reveal its well-defined single-site active species within its silicate network. Electron microscopies confirm its Hollow-shell-structured mesoporous material. As presented in this study, the newly constructed heterogeneous catalyst enables an efficient Suzuki-Miyaura cross-coupling reaction for a range of substrates with up to 95% yield in mild conditions. Meanwhile, the HS@PdPPh2@MSN possessed excellent stability and recyclability, which could be reused at least five times without significant loss of activity. Furthermore, the HS@PdPPh2@MSN is easily synthesized and cost-effective, which makes it a candidate for applications in fine chemical engineering.