Oxygen Complexes And Oxygen Activation By Transition Metals

This monograph consists of manuscripts, summary statements, and poster abstracts submitted by invited speakers and poster contributors who participated in the symposium "Oxygen Complexes and Oxygen Activation by Transition Metals," held March 23-26, 1987, at Texas A&M University. This meeting was the fifth annual international symposium sponsored by the Texas A&M Industry-University Cooperative Chemistry Program (IUCCP). The co chairmen of the conference were Professors Arthur E. Martell and Donald T. Sawyer of the Texas A&M University Chemistry Department. The program was developed by an academic-industrial steering committee consisting of the co-chairmen and members appointed by the sponsoring chemical companies Dr. James F. Bradzil, The Standard Oil Company, Ohio; Dr. Jerry R. Ebner, Monsanto Company; Dr. Craig Murchison, Dow Chemical Company; Dr. Donald C. Olsen, Shell Development Company; Dr. Tim R. Ryan, Celanese Chemical Company; and Dr. Ron Sanderson, Texaco Chemical Company. The subject of this conference reflects the intense interest that has developed in academic institutions and industry on several aspects of dioxygen chemistry. These include the formation of dioxygen complexes and their applications in facilitated transport and oxygen separation; homo geneous and heterogeneous catalysis of oxidation; and oxygenation of organic substrates by molecular oxygen. The conference differs in two respects from several other symposia on dioxygen chemistry held during the past few years. First, there is extensive industrial participation, especially with respect to oxygen activation.

hemistry is the science about breaking and forming of bonds between atoms. One of the most important processes for organic chemistry is breaking bonds C–H, as well as C–C in various compounds, and primarily, in hydrocarbons. Among hydrocarbons, saturated hydrocarbons, alkanes (methane, ethane, propane, hexane etc. ), are especially attractive as substrates for chemical transformations. This is because, on the one hand, alkanes are the main constituents of oil and natural gas, and consequently are the principal feedstocks for chemical industry. On the other hand, these substances are known to be the less reactive organic compounds. Saturated hydrocarbons may be called the “noble gases of organic chemistry” and, if so, the first representative of their family – methane – may be compared with extremely inert helium. As in all comparisons, this parallel between noble gases and alkanes is not fully accurate. Indeed the transformations of alkanes, including methane, have been known for a long time. These reactions involve the interaction with molecular oxygen from air (burning – the main source of energy!), as well as some mutual interconversions of saturated and unsaturated hydrocarbons. However, all these transformations occur at elevated temperatures (higher than 300–500 °C) and are usually characterized by a lack of selectivity. The conversion of alkanes into carbon dioxide and water during burning is an extremely valuable process – but not from a chemist viewpoint.

The activation of dioxygen by metal ions has both synthetic potential and biological relevance. Dioxygen is the cleanest oxidant for use in emission-free technologies to minimize pollution of the environment. The book gives a survey of those catalyst systems based on metal complexes which have been discovered and studied in the last decade. They activate molecular oxygen and effect the oxidation of various organic compounds under mild conditions. Much of the recent progress is due to a search for biomimetic catalysts that would duplicate the action of metalloenzymes. Mechanistic aspects are emphasized throughout the book. An introductonary chapter reviews the chemistry of transition metal dioxygen complexes, which are usually the active intermediates in the catalytic reactions discussed. Separate chapters are devoted to oxidation of saturated, unsaturated and aromatic hydrocarbons, phenols, catechols, oxo-compounds, phosphorus, sulfur and nitrogen compounds.

The subject of dioxygen activation and homogeneous catalytic oxidation by metal complexes has been in the focus of attention over the last 20 years. The widespread interest is illustrated by its recurring presence among the sessions and subject areas of important international conferences on various aspects of bioinorganic and coordination chemistry as well as catalysis. The most prominent examples are ICCC, ICBIC, EUROBIC, ISHC, and of course the ADHOC series of meetings focusing on the subject itself. Similarly, the number of original and review papers devoted to various aspects of dioxygen activation are on the rise. This trend is due obviously to the relevance of catalytic oxidation to biological processes such as dioxygen transport, and the action of oxygenase and oxidase enzymes related to metabolism. The structural and functional modeling of metalloenzymes, particularly of those containing iron and copper, by means of low-molecular complexes of iron, copper, ruthenium, cobalt, manganese, etc., have provided a wealth of indirect information helping to understand how the active centers of metalloenzymes may operate. The knowledge gained from the study of metalloenzyme models is also applicable in the design of transition metal complexes as catalytsts for specific reactions. This approach has come to be known as biomimetic or bioinspired catalysis and continues to be a fruitful and expanding area of research.

Since the classic work Metal-Catalyzed Oxidations of Organic Compounds (edited by R A Sheldon and J K Kochi, 1991), no book has been devoted to advances in the field of biomimetic oxidations, which was created nearly 18 years ago. This expanding research field is covered in this volume. All the different aspects of the modeling of oxidations catalyzed by metalloenzymes are dealt with. This invaluable book will be useful to postgraduates as well as researchers in academia and industry, and will also benefit second year university students. Contents:Thermodynamic Influences of C–H Bond Oxidation (J M Mayer)Distinguishing Biomimetic Oxidations from Oxidations Mediated by Freely Diffusing Radicals (K U Ingold & P A MacFaul)Biomimetic Oxygenations Related to Cytochrome P450: Metal-Oxo and Metal-Peroxo Intermediates (J L McLain et al.)Models of Heme Peroxidases and Catalases (B Meunier)Non-Heme Peroxidases and Catalases: Mechanistic Implications from the Studies of Manganese and Vanadium Model Compounds (C Slebodnick et al.)Methane Monooxygenase Models (Z-B Hu & S M Gorun)Models of Copper Enzymes and Heme-Copper Oxidases (M A Kopf & K D Karlin)Iron-Containing Models of Catechol Dioxygenases (H-J Krüger)Biomimetic Chemistry of Molybdenum (C G Young)Models of Superoxide Dismutases (D E Cabelli et al.)Modeling the Oxygen-Evolving Complex in Photosystem II (J Limburg et al.)Asymmetric Biomimetic Oxidations (A Robert & B Meunier)Bioinspired Oxidations Catalyzed by Ruthenium Complexes (S-I Murahashi & N Komiya)Biocatalytic and Biomimetic Oxidations from an Industrial Perspective (R A Sheldon) Readership: Postgraduate students and researchers in biochemistry and chemistry. Keywords:EPR Spectroscopy;Functional Model Chemistry;Isotope Labeling;Manganese Complexes;Mechanism;Oxygen Evolution;Photosystem II;Redox Chemistry;Water Splitting Chemistry;X-Ray Spectroscopy;Oxidation;Oxygenation;Transition Metal Complexes;Asymmetric Oxidation;Oxidase;Oxygenase;Metal-Oxo;Peroxide, Peroxo;Metalloporphyrin;MMO Models;P450 Models

This monograph consists of the proceedings of the Fifth International Symposium on the Activation of Dioxygen and Homogeneous Catalytic Oxidation, held in College Station, Texas, March 14-19, 1993. It contains an introductory chapter authored by Professors D. H. R. Barton and D. T. Sawyer, and twenty-nine chapters describing presentations by the plenary lecturers and invited speakers. One of the invited speakers, who could not submit a manuscript for reasons beyond his control, is represented by an abstract of his lecture. Also included are abstracts of forty-seven posters contributed by participants in the symposium. Readers who may wish to know more about the subjects presented in abstract form are invited to communicate directly with the authors of the abstracts. This is the fifth international symposium that has been held on this subject. The first was hosted by the CNRS, May 21-29, 1979, in Bendor, France (on the Island of Bandol). The second meeting was organized as a NATO workshop in Padova, Italy, June 24-27, 1984. This was followed by a meeting in Tsukuba, Japan, July 12-16, 1987. The fourth symposium was held at Balatonfured, Hungary, September 10-14, 1990. The sixth meeting is scheduled to take place in Delft, The Netherlands (late Spring, 1996); the organizer and host will be Professor R. A. Sheldon.

Explores both electrochemistry fundamentals and the applications of oxygen in electrochemical systems. Much of the information is summarized in tables which are accompanied by a list of references to consult for details. Emphasizes fuel cells and metal/air batteries.