Novel Monolayer Protected Clusters as Supports for Catalysts

Novel Monolayer Protected Clusters as Supports for Catalysts
Author: Kurt Edward Kershaw
Publisher:
Total Pages:
Release: 2003
Genre:
ISBN:

This thesis details the design and synthesis of functional nanoparticles based on the assembly of modified thioctic acid derivatives; the majority of which contain a 2-aryl-2-oxazoline fragment. The oxazoline molecules studied herein were prepared by the treatment of an arylcyanide or related precursor with an appropriate amino-alcohol in the presence of a Lewis acid catalyst. Molecules designed for attachment to Au surfaces to function as surface "linker" (oxazoline ligand-containing) and "spacer" (ligand-free) fragments were made by the coupling of amines or alcohols to thioctic acid chloride or 'via' coupling of thioctic acid itself with primary amines (DCC protocols) to yield the desired amides. Gold monolayer protected clusters (WC's) derivatised with the linker fragments were prepared 'via' the Schiffron reaction. The use of these synthetic MPC's as catalysts for the Ni/Al-mediated cyclotrimerization of 2-cyclohexene-1-one and trimethylsilyl-acetylene was examined.

Supported Catalysts, from Polymers to Gold Nanoparticles Supports

Supported Catalysts, from Polymers to Gold Nanoparticles Supports
Author: William J. Sommer
Publisher:
Total Pages:
Release: 2007
Genre: Catalysts
ISBN:

In today's world, the need to limit the use of nonrenewable resources and the importance of recycling has been recognized. One important contribution of chemists toward the general goal of limiting their use is to find catalysts that can be reused and recycled thereby limiting the need for expensive metal precursors and metal waste. Strategies to recycle catalysts are multifold and range from the employment of soluble polymers as catalyst supports to the use of membrane-encapsulated catalyst. The use of soluble polymers as a support not only offers the advantage of being soluble under the catalytic reaction conditions but also, to be removable by changing the conditions of the surrounding media. Despite the great potential of these soluble supported catalysts, their use is very limited in today's synthesis. In addition, no set of rules have been established to guide the synthesis of efficient supported catalysts. In order to establish a "tool box" for the synthesis of supported catalysts, the study of several parameters such as the choice of the support and the choice and the stability of the catalyst are necessary. To establish this set of rules, a limited number of catalytic transformations, were studied. These catalytic reactions are the Heck-Mizoroki, Suzuki-Miyaura and Sonogashira coupling reactions. These transformations became fundamental for the synthesis of drugs and materials. The first and second chapters provide background information by describing and evaluating the main supports that were previously used for catalysts and the two main catalysts that are used in this thesis, the palladium pincer complex and the palladium N-heterocyclic complex. In chapter 3, the synthesis of a soluble polymer supported catalyst is described. The polymer chosen for the study is poly(norbornene), and the catalyst is a 1,3-disubstituted benzene ligand with sulfurs in the side-chains able to chelate to the metal center, better known as pincer ligand. These ligands are abbreviated by the three atoms that coordinate to the metal center, in this study, SCS. The metal used for the investigation of the activity of this supported pincer is palladium. The importance of the nature of the linkage on the stability of the Pd-SCS pincer complex has been reported in the literature, leading to the synthesis of Pd-SCS pincer complex tethered to the polymer via an ether and an amide linkage. The synthesized poly(norbornene) supported Pd-SCS pincer complexes were evaluated using the Heck transformation of iodobenzene with n-butyl acrylate. Kinetic studies and leaching tests using poly(vinyl pyridine) and mercury were carried out resulting in the conclusion that the active species during the catalysis is not the palladium pincer complex but a leached palladium (0) species. In chapter 4, Pd-PCP pincer complexes with the ether and amide tether were synthesized. Kinetic and poisoning studies were carried out resulting in a similar conclusion. Furthermore, 31P NMR experiments were conducted to investigate the unstability of the complex. Following this study, in-situ XAS as well as computational calculations were carried out. The conclusion from this investigation argues that triethylamine is a key ingredient for the decomposition of the Pd-PCP complex. The overall conclusion from these two different studies is thta Pd(II) pincer complexes decomposes during the Heck reaction when triethylamine is used for the coupling of iodobenzene to n-butyl acrylate in DMF at 120°C. Stemming from this investigation, a reported more stable complex, Pd-NHC, was tethered onto poly(norbornene). The system was evaluated using Suzuki-Miyaura, Heck and Sonogashira reactions. Similar poisoning and kinetic studies were utilized to investigate the stability of the supported NHC Pd complexes. The result of this investigation suggests that supported Pd-NHC complexes are stable under Suzuki-Miyaura and Sonogashira but decompose under Heck conditions. However, when the system was recycled, a decrease in activity for the Suzuki-Miyaura transformation and solubility was observed. In chapter 6, gold monolayer protected clusters (MPC) were investigated as potential candidates as supports. To examine the potential of MPC as a support, a NHC-Pd complex was graphted onto the particles. To functionalize the gold nanoparticles, a new method was developed. Using azide moieties added to the gold nanoparticles, the catalyst was added via microwave assisted 1,3 dipolar cycloaddition. The system was evaluated using Suzuki-Miyaura transformations under microwave conditions. The system exhibited quantitative conversions for a variety of substrates. However, when the system was recycled, aggregation of the particles and decrease in catalytic activity was observed. In summary, this thesis describes the synthesis and evaluation of poly(norbornene) supported Pd-pincer and Pd-NHC complexes and of gold nanoparticles supported Pd-NHC complex. It also detail the combination of kinetic and poisoning studies developed to evaluate a potential supported catalyst.

Protected Metal Clusters: From Fundamentals to Applications

Protected Metal Clusters: From Fundamentals to Applications
Author:
Publisher: Elsevier
Total Pages: 394
Release: 2015-09-06
Genre: Technology & Engineering
ISBN: 0444635025

Protected Metal Clusters: From Fundamentals to Applications surveys the fundamental concepts and potential applications of atomically precise metal clusters protected by organic ligands. As this class of materials is now emerging as a result of breakthroughs in synthesis and characterization that have taken place over the last few years, the book provides the first reference with a focus on these exciting novel nanomaterials, explaining their formation, and how, and why, they play an important role in the future of molecular electronics, catalysis, sensing, biological imaging, and medical diagnosis and therapy. Surveys the fundamental concepts and potential applications of atomically precise metal clusters protected by organic ligands. Provides well-organized, tutorial style chapters that are ideal for teaching and self-study In-depth descriptions by top scientists in the field Presents the state-of-the art of protected metal clusters and their future prospects

Supported Catalysts and Their Applications

Supported Catalysts and Their Applications
Author: David C Sherrington
Publisher: Royal Society of Chemistry
Total Pages: 282
Release: 2007-10-31
Genre: Science
ISBN: 1847551963

The need to improve both the efficiency and environmental acceptability of industrial processes is driving the development of heterogeneous catalysts across the chemical industry, including commodity, specialty and fine chemicals and in pharmaceuticals and agrochemicals. Drawing on international research, Supported Catalysts and their Applications discusses aspects of the design, synthesis and application of solid supported reagents and catalysts, including supported reagents for multi-step organic synthesis; selectivity in oxidation catalysis; mesoporous molecular sieve catalysts; and the use of Zeolite Beta in organic reactions. In addition, the two discrete areas of heterogeneous catalysis (inorganic oxide materials and polymer-based catalysts) that were developing in parallel are now shown to be converging, which will be of great benefit to the whole field. Providing a snapshot of the state-of-the-art in this fast-moving field, this book will be welcomed by industrialists and researchers, particularly in the agrochemicals and pharmaceuticals industries.

Nanomaterials in Catalysis

Nanomaterials in Catalysis
Author: Philippe Serp
Publisher: John Wiley & Sons
Total Pages: 741
Release: 2012-11-15
Genre: Science
ISBN: 3527656898

Nanocatalysis has emerged as a field at the interface between homogeneous and heterogeneous catalysis and offers unique solutions to the demanding requirements for catalyst improvement. Heterogeneous catalysis represents one of the oldest commercial applications of nanoscience and nanoparticles of metals, semiconductors, oxides, and other compounds have been widely used for important chemical reactions. The main focus of this fi eld is the development of well-defined catalysts, which may include both metal nanoparticles and a nanomaterial as the support. These nanocatalysts should display the benefits of both homogenous and heterogeneous catalysts, such as high efficiency and selectivity, stability and easy recovery/recycling. The concept of nanocatalysis is outlined in this book and, in particular, it provides a comprehensive overview of the science of colloidal nanoparticles. A broad range of topics, from the fundamentals to applications in catalysis, are covered, without excluding micelles, nanoparticles in ionic liquids, dendrimers, nanotubes, and nanooxides, as well as modeling, and the characterization of nanocatalysts, making it an indispensable reference for both researchers at universities and professionals in industry.

Atomically Precise Metal Nanoclusters

Atomically Precise Metal Nanoclusters
Author: Zhikun Wu
Publisher: Morgan & Claypool Publishers
Total Pages: 141
Release: 2020-11-06
Genre: Science
ISBN: 1636390250

Atomically precise metal nanocluster research has emerged as a new frontier. This book serves as an introduction to metal nanoclusters protected by ligands. The authors have summarized the synthesis principles and methods, the characterization methods and new physicochemical properties, and some potential applications. By pursuing atomic precision, such nanocluster materials provide unprecedented opportunities for establishing precise relationships between the atomic-level structures and the properties. The book should be accessible to senior undergraduate and graduate students, researchers in various fields (e.g., chemistry, physics, materials, biomedicine, and engineering), R&D scientists, and science policy makers.

Supported Metal Single Atom Catalysis

Supported Metal Single Atom Catalysis
Author: Philippe Serp
Publisher: John Wiley & Sons
Total Pages: 912
Release: 2022-02-09
Genre: Technology & Engineering
ISBN: 3527830170

b”Supported Metal Single Atom CatalysisCovers all key aspects of supported metal single atom catalysts, an invaluable resource for academic researchers and industry professionals alike Single atom catalysis is one of the most innovative and dynamic research areas in catalysis science. Supported metal catalysts are used extensively across the chemical industry, ranging from fine and bulk chemical production to petrochemicals. Single atom catalysts (SACs) combine the advantages of both homogeneous and heterogeneous catalysts such as catalyst stability, activity, and high dispersion of the active phase. Supported Metal Single Atom Catalysis provides an authoritative and up-to-date overview of the emerging field, covering the synthesis, preparation, characterization, modeling, and applications of SACs. This comprehensive volume introduces the basic principles of single atom catalysis, describes metal oxide and carbon support materials for SAC preparation, presents characterization techniques and theoretical calculations, and discusses SACs in areas including selective hydrogenation, oxidation reactions, activation of small molecules, C-C bond formation, and biomedical applications. Highlights the activity, selectivity, and stability advantages of supported metal SACs compared to other heterogeneous catalysts Covers applications of SACs in thermal catalysis, electrocatalysis, and photocatalysis Includes chapters on single atom alloys and supported double and triple metal atom catalysts Discusses the prospects, challenges, and potential industrial applications of SACs Supported Metal Single Atom Catalysis is an indispensable reference for all those working in the fields of catalysis, solid-state chemistry, materials science, and spectroscopy, including catalytic chemists, organic chemists, electrochemists, theoretical chemists, and industrial chemists.

Recent Advances in Nanoparticle Catalysis

Recent Advances in Nanoparticle Catalysis
Author: Piet W.N.M. van Leeuwen
Publisher: Springer Nature
Total Pages: 460
Release: 2020-07-01
Genre: Science
ISBN: 3030458237

This book provides an overview of the latest developments in the field of nanoparticle catalysis. It not only discusses established topics in detail, but also explores several emerging topics. Catalysis with nanoparticles is expanding exponentially and is attracting significant interest due to the many exciting findings being reported. Mastering the synthesis, characterization, stabilization and use of these catalysts offers numerous possibilities that far exceed those of classic heterogeneous and homogeneous catalysis.