Molecular and Gold Nanoparticles Supported N-Heterocyclic Carbene Silver(I) Complexes – Synthesis, Characterization and Catalytic Applications

• Main Authors: Zhao-zeng wang, 王趙增
• Other Authors: Joyce Shuchun Yu
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/32794899723457667816

碩士 === 國立中正大學 === 化學所 === 97 === Two major subjects were discussed in this thesis. The first part was focused on synthesis and catalytic reactivity of molecular silver (I) N-heterocyclic carbene complexes. The second part is the study of the hybrid catalyst consisting of Ag(I) NHC complexes supported on gold nanoparticles surfaces. We have successfully synthesized thess two catalysts the silver (I) N-heterocyclic carbene complexes [Ag(hmim)2]PF6 (3) and Au NPs-(NHC)2-Ag(I)PF6 (10), where hmim = 1-hexyl-3-methylimidazolium, by direct reaction of Ag2O and imidazolium salts in the presence of KOtBu. The complex 3 was characterized by 1H- and 13C-NMR, IR, UV, ESI-MS, X-ray crystallography. The di-coordinated, Ag(I) adopted linear geometry with one PF6? as counter anion. The complex 10 was characterized by 1H-NMR, IR, UV, and TEM. Hybrid catalysts of this type were dissolvable and precipitable, and their structures and reactions were investigated by solution phase NMR spectroscopy with a resolution typically attainted for soluble systems. The three component coupling reactions of aldehydes, alkynes, and amines (A3-coupling) has attracted much attention for its coupling products, propargylamines, as major skeletons or building blocks for the preparation of many nitrogen-containing biologically active compounds. In the current study, silver NHC complexes in both molecular and hybrid forms were found to be effective catalyst for a series of A3-coupling reactions of aliphatic- and aromatic aldehydes with secondary amines and terminal alkynes. With a catalyst loading of 1.5 ~ 3.0 mol% of 3 and 10. The coupling reactions can be completed in hours in CH3CH2CN at 97 oC. The 3-catalyzed A3-coupling reactions can be further accelerated under microwave irradiation conditions to give desired products in 85-94% yields in 30-60 seconds. In the presence of Au NPs–NHC–Ag(I) (20 mol %) 10, the A3-coupling reactions were carried out at ambient temperature and in a solventless condition to give the corresponding products > 95% yields within 2 hours. The hybrid catalyst 10 can be quantitatively recovered and effectively recycled by centrifugation and simple filtration of the reaction mixtures. The recovered catalyst was used directly without further purification for 12 consecutive cycles without any loss of reactivity.