Metal Ligand Co Operativity

This book provides researchers in the fields of organic chemistry, organometallic chemistry and homogeneous catalysis with an overview of significant recent developments in the area of metal-ligand cooperativity, with a focus on pincer architectures. The various contributions highlight the widespread impact of M–L co-operativity phenomena on modern organometallic chemistry and catalyst development. The development of efficient and selective catalytic transformations relies on the understanding and fine control of the various elementary reactions that constitutes a catalytic cycle. Co-operative ligands, which actively participate in bond making and bond breaking together to the metal they support, open up new avenues in this area. In particular, buttressing a weak or reactive metal-ligand bond by flanking coordinating arms in a pincer ligand design is proving a versatile strategy to access robust metal complexes that exhibit unusual and selective reactivity patterns.

Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Brønsted base catalysis to e.g. metal-assisted organo catalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating activating groups, and describe in detail the different strategies of cooperative activation, highlighting their respective advantages and pitfalls. As a result, readers will learn about the different concepts of cooperative catalysis, their corresponding modes of operation and their applications, thus helping to find a solution to a specific synthetic catalysis problem.

Metal-ligand interactions are currently being studied in different fields, from a variety of points of view, and recent progress has been substantial. Whole new classes of compounds and reactions have been found; an arsenal of physical methods has been developed; mechanistic detail can be ascertained to an increasingly minute degree; and the theory is being developed to handle systems of ever-growing complexity. As usual, such multidisciplinarity leads to great opportunities, coupled with great problems of communication between specialists. It is in its promotion of interactions across these fields that Metal-Ligand Interactions: From Atoms, to Clusters, to Surfaces makes its timely contribution: the tools, both theoretical and experimental, are highly developed, and fundamental questions remain unanswered. The most fundamental of these concerns the nature of the microscopic interactions between metal atoms (clusters, surfaces) and ligands (atoms, molecules, absorbates, reagents, products) and the changes in these interactions during physical and chemical transformation. In Metal-Ligand Interactions, leading experts discuss the following, vital aspects: ab initio theory, semi-empirical theory, density functional theory, complexes and clusters, surfaces, and catalysis.

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Proceedings of the NATO Advanced Study Institute, held in Cetraro, Italy, from 1 to 12 September 2002

This book presents recent advances in dinuclear complexes in which the metal-metal cooperative effect operates for obtaining substrate activation and high performance catalysts. Catalysis continues to be a fast expanding area to design efficient tools in synthesis and in industrial chemistry. It allows performing syntheses with short reaction times, atom economy, reduced consumption of energy and loss of reagents, and low level of wastes. Dinuclear complexes are known to be more efficient than the mononuclear analogues for the reaction rates and the selectivities. This book analyses the latest research, focusing on the key concepts, in building and using these dinuclear complexes. The book is aimed at researchers, graduate students and chemists at all levels in academia and industry.

The development of new and efficient catalysts plays an important role in chemical research. The inspiration for finding new catalysts includes long-term benefits such as (a) efficient, atom-economical reactions; (b) chemoselective reactions under mild conditions, obviating the need for protection and deprotection of functional groups; and (c) reduction of chemical waste in the production of fine chemicals for pharmaceuticals. For these purposes, artificial enzyme mimics are exploited. In the preparation of such catalysts, a promising approach is to translate the principles of enzyme catalysis for the design of new catalytic materials. In this research, we used design features of the cooperativity of Lewis acid transition metals and heterocyclic ligands designed to provide hydrogen bond donor (A) and acceptor (B), inspired by Nature's enzymes, to catalyze reactions of polar molecules such as water, alcohols, or amines with organic molecules.* To synthesize our catalysts, we envisioned anchoring a transition metal to a heterocycle which features a reasonably acidic N-H group (A). In this research, we prepared 10 pyrazole ligands and 35 of their complexes, 15 of which were analyzed by X-ray diffraction. Furthermore, isoelectronic and isosteric complexes incapable of donating or accepting hydrogen bond(s) were also synthesized to determine the relationship between hydrogen-bond donating properties and catalytic efficiency. All the complexes were characterized by NMR spectroscopy, IR spectroscopy, and elemental analysis. Part of our studies to date have focused on the hydrolysis of unactivated amide bonds, thought to be a more difficult challenge than similar reactions of phosphate diesters. We also focused on the use of hydrogen-donating-group-assisted in catalysis of chemoselective hydrogenation of imines. We also used bifunctional catalysts to catalyze regio- and stereoselective dimerization of terminal alkynes, and hydrogen transfer hydrogenation of aldehydes, ketones, and imines. The catalysts can also catalyze cyclization and coupling reactions of alkynols. Significantly, these catalytic processes involve both C-C and C-O bond formation with diastereo- and regioselectivity. These results are fruitful because we have opened another field of catalysis using the combined effects of hydrogen-bond donating ligands and Lewis acidic transition metals. *Please refer to dissertation for diagrams.

The design of ancillary ligands used to modify the structural and reactivity properties of metal complexes has evolved into a rapidly expanding sub-discipline in inorganic and organometallic chemistry. Ancillary ligand design has figured directly in the discovery of new bonding motifs and stoichiometric reactivity, as well as in the development of new catalytic protocols that have had widespread positive impact on chemical synthesis on benchtop and industrial scales. Ligand Design in Metal Chemistry presents a collection of cutting-edge contributions from leaders in the field of ligand design, encompassing a broad spectrum of ancillary ligand classes and reactivity applications. Topics covered include: Key concepts in ligand design Redox non-innocent ligands Ligands for selective alkene metathesis Ligands in cross-coupling Ligand design in polymerization Ligand design in modern lanthanide chemistry Cooperative metal-ligand reactivity P,N Ligands for enantioselective hydrogenation Spiro-cyclic ligands in asymmetric catalysis This book will be a valuable reference for academic researchers and industry practitioners working in the field of ligand design, as well as those who work in the many areas in which the impact of ancillary ligand design has proven significant, for example synthetic organic chemistry, catalysis, medicinal chemistry, polymer science and materials chemistry.