Catalysis by Metal Complexes – serie

The demand for selective organic reactions is growing more acute everyday. Indeed, greater product selectivity has an important impact on energy and resource utilization, in terms of reduced process energy requirements for product separation and purification, in terms of low-value by-products, and in terms of environmental acceptance and compatibility. Moreover, more and more chemicals, especially pharmaceuticals, have to be sold in an optically active form. The search for selectivity constitutes a tremendous challenge for the chemists. In the last two decades, homogeneous transition metal based catalysis has emerged as one of the most promising tools for obtaining selectivity. In connection with developments in this area, this book contains updated and expanded versions of most of the lectures presented at a Cornett course held in Trieste (Italy) in 1989 and sponsored by the European Community. A primary aim is to cultivate a deeper understanding of the parameters that govern the selectivities and stimulate a wider utilization of transition metal based catalysis in organic synthesis. All aspects of selectivity, chemo-, regio-, stereo- and enantioselectivity are considered and illustrated by applications in various fields or organic synthesis. The impact of catalysis in oxydation, reduction, carbonylation reactions, carbene chemistry, in Ni and Pd promoted dimerizations, oligomerizations as well as fonctionalisations is stressed, quite often with special emphasis laid on reaction mechanisms. In this aspect, the last chapter examplifies the interest of high pressure NMR and IR when investigating the nature of reaction intermediates in homogeneous reactions.

Hydrogen peroxide is a chemical that is becoming increasingly fashionable as an oxidant, both in industry and in academia and whose production is expected to increase significantly in the next few years. This growth in interest is largely due to environmental considerations related to the clean nature of hydrogen peroxide as an oxidant, its by-product being only water.To date this chemical has largely been employed as a non-selective oxidant in operations like the bleaching of paper, cellulose and textiles, or in the formulation of detergents, and only to a minimal extent in the manufacture of organic chemicals.This book has been organized to cover the different aspects of the chemistry of hydrogen peroxide. The various chapters into which the book is divided have been written critically by the authors with the general aim of stimulating new ideas and emphasizing those aspects that are likely to lead to new developments in organic synthesis in the coming future.

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.

Photosensitization and photocatalysis refer to processes by which permanent chemical transformations are induced on substrates (organic/inorganic) by radiation to which the substrates themselves are transparent. Such transformations can be highly specific, very efficient, and occur under mild conditions. Herein lies the power of photochemical methods for possible applications in the field of conversion and storage of solar energy. This book provides a recent survey of the progress in this important area in catalysis, with an emphasis on inorganic complexes and organometallic compounds as the key light aborbers. The book is organized in three parts: fundamentals, followed by applications. Discussions cover a wide variety of photosensitized or photocatalyzed reactions: decomposition of water, reduction of CO2 and CO; spectral sensitization in photoelectrochemical cells; transformations (oxidation, reduction, isomerization, hydrogenation, dehydrogenation, carbonylation, etc.) of organics such as alkanes, alkenes, alcohols, etc.In view of the variety of systems (sensitizers, substrates) and the topics covered, the volume is unique in the field of photochemistry and will appeal to academic and industrial researchers in various subdisciplines of chemistry, material science and catalysis.

Homogeneous hydrogenation is one of the most thoroughly studied fields of homogeneous catalysis. The results of these studies have proved to be most important for an understanding of the underlying principles of the activation of small molecules by transition metal complexes. During the past three decades homogeneous hydrogenation has found widespread application in organic chemistry, including the production of important pharmaceuticals, especially where a sophisticated degree of selectivity is required.This volume presents a general account of the main principles and applications of homogeneous hydrogenation by transition metal complexes. Special attention is devoted to the mechanisms by which these processes occur, and the role of the recently discovered complexes of molecular hydrogen is described. Sources of hydrogen, other than H2, are also considered (transfer hydrogenation). The latest achievements in highly stereoselective hydrogenations have made possible many new applications in organic synthesis. These applications are documented by giving details of the reduction of important unsaturated substrates (alkenes, alkynes, aldehydes and ketones, nitrocompounds, etc.). Hydrogenation in biphasic and phase transfer catalyzed systems is also described. Finally, a discussion of the biochemical routes of H2 activation highlights the similarities and differences in performing hydrogenation in both natural and synthetic systems.For researchers working in the fields of homogeneous catalysis, especially in areas such as pharmaceuticals, plastics and fine chemicals.

Born and initially developed in various industrial laboratories, mainly in U.S.A. and Gennany, homogeneous phase catalytic carbon monoxide hydrogenation and alcohols and their derivatives carbonylation and homologation, have generally been considered and reviewed separately in the course of their 40 years history without concern for common aspects in the chemical transfonnations and in catalysis. Thanks to researchers of Japanese companies participating in the National C 1 Chemistry Project (1980-1987) the scientific and technical approaches in this field have been unified and applied in parallel, in the light of some common aspects of the chemical reactions and mechanisms. Now, at a moment when research seems becahned, a general presentation and discussion of the most recent topics might be an useful basis for further development of this chemistry. To delimit and simplify the discussion of the chemical aspects and the nature of the catalysts involved, the present review is limited to reactions employing homogeneous metal complexes for the direct conversion of syngas to oxygenates and to the hydrocarbonylation of these last to homologous derivatives. Since the previous practically contemporary reviews by Dombek [in Adv. Organomet. Chern. (1983)] on CO hydrogenation and by the present authors [in Asp.Homog.Catal.(Reidel Pu.l984)] on alcohol homologation fully cover the literature up to 1982, here we mainly refer to work done after 1982, and consider the cited reviews as covering the historical development of research in the 1940- 1980 period.

Oxidative catalysis by metalloporphyrin systems occupies a prominent role in the current research in the fields of chemical and biological catalysis. Our particular interest and approach has been to collect in the same volume papers dealing with both the chemical and biological aspects of the reactivity of heme systems because of the realization that a better understanding of the complementary discipline can be extremely useful for the researchers from either field. The current progress of the research on synthetic metalloporphyrin catalysts has led to the development of several systems that are able to reproduce the heme-enzyme mediated oxygenation and oxidation reactions, at least in terms of reaction types, mechanisms and often rates. These achievements have stimulated the of creating metalloporphyrin catalysts which are both ambitious project efficient and stable enough to become competitive for large-scale industrial processes. Although this project is still far from being realized, the efforts in this direction parallel those aimed at the application of heme enzymes to chemical technologies, e. g. for the mild, selective oxidation of organics or the detoxification of pollutants. Both the two approaches will be advantageous because while the enzyme systems can achieve selectivities which are probably unattainable by synthetic catalysts, the latter can be active under experimental conditions that would readily inactivate the enzymes.

Homogeneous catalysis plays an important role both in the laboratory and in the industry. Successful applications in industry involve new polymerisation processes with complexes of zirconium and related metals, new carbonylation processes employing palladium and rhodium, ring opening polymerisations, and new enantioselective isomerisation catalysts as in the preparation of menthol. Also in the synthesis of organic compounds in the laboratory highly selective homogeneous catalysts represent an irreplaceable part of the toolbox of the synthetic chemist. Examples of such reactions are cross-coupling (Ni, Pd), nucleophilic substitution of allylpalladium complexes, Heck reactions (Pd), asymmetric epoxidation, Wacker type reactions (Pd), asymmetric hydrogenations (Rh, Ru), reactions of chromium complexes, enantioselective reactions with Lewis acids, reactions with the McMurry reagent, etc. There is hardly any multistep organic synthesis that does not involve one of these metal catalysed reactions. Most of these catalysts have been developed by empiricism.The metal catalysed processes consist of a series of elementary steps which often have been studied in isolation in organometallic chemistry. The knowl- edge of such elementary steps - effect ofligands, anions, coordination number, valence states - has greatly contributed to the development of improved cata- lysts for the reactions mentioned above. In addition to the empirical approach theoretical methods have given support and guidance to the development of improved processes. Often the key steps of a cycle escape from a direct ob- servation and then theoretical contributions are even more wanted.

Oxygenases have been the subject of much study and are of great interest and application. Biomimetic chemistry of oxygenases has yielded clarification of enzyme structures and reaction mechanisms and has also led to the development of synthetic oxygenation processes. This volume contains 8 chapters written by leading researchers which together present an overview of di- and mono-oxygenases and their model systems from the point of view of functions, structures and mechanisms. An up-to-date clarification of structures around active centres of heme- and nonheme-oxygenases is given, with reference to the design of model complexes. Various contributions also discuss in detail the formation, structure and reactivity of metal-oxygen and metal-substrate species in both enzyme and model systems. The contents of the volume address the interface between bioinorganic chemistry and homogeneous catalysis and contains much to emphasize the importance of catalytic studies in bio- and biomimetic chemistry.

This text is a critical overview of all of the published literature in the field of reductive carbonylation of organic nitro compounds (mainly nitroarenes) and related reactions. It comprises six chapters respectively dealing with structure and complexes of nitro compounds, the synthesis of isocyanates, the synthesis of carbamates and ureas, the synthesis of other non-cyclic compounds, such as amines, imines, and mechanistic studies.

This monograph is devoted to the activation and various transformations of saturated hydrocarbons (alkanes) - reactions accompanied by the C--H and C--C bond cleavage. Alkanes are the main constituents of oil and natural gas, and consequently are the principal feedstocks for the chemical industry. On the other hand, these substances are known to be the least reactive organic compounds. Special attention is paid to the recently found alkane activations in the presence of metal complexes, which are described in more detail. In addition to the reactions of saturated hydrocarbons which are the main topic of this book, the activation of C--H bonds in arenes and even olefins and acetylenes are considered.

In the last decade there have been numerous advances in the area of rhodium-catalyzed hydroformylation, such as highly selective catalysts of industrial importance, new insights into mechanisms of the reaction, very selective asymmetric catalysts, in situ characterization and application to organic synthesis. The views on hydroformylation which still prevail in the current textbooks have become obsolete in several respects. Therefore, it was felt timely to collect these advances in a book. The book contains a series of chapters discussing several rhodium systems arranged according to ligand type, including asymmetric ligands, a chapter on applications in organic chemistry, a chapter on modern processes and separations, and a chapter on catalyst preparation and laboratory techniques. This book concentrates on highlights, rather than a concise review mentioning all articles in just one line. The book aims at an audience of advanced students, experts in the field, and scientists from related fields. The didactic approach also makes it useful as a guide for an advanced course.

Over the past 20 years aqueous organometallic catalysis has found applications in small- scale organic synthesis in the laboratory, as well as in the industrial production of chemicals with a combined output close to one million tons per year. Aqueous/organic two-phase reactions allow easy product-catalyst separation and full catalyst recovery which mean clear benefits not only in economic but also in environmental and green chemistry contexts. Instead of putting together a series of expert reviews of specialized fields, this book attempts to give a comprehensive yet comprehensible description of the various catalytic transformations in aqueous systems as seen by an author who has been working on aqueous organometallic catalysis since its origin. Emphasis is put on the discussion of differences between related non-aqueous and aqueous processes due to the presence of water. The book will be of interest to experts and students working in catalysis, inorganic chemistry or organic synthesis, and may serve as a basis for advanced courses.

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.

In the last decade there have been numerous advances in the area of rhodium-catalyzed hydroformylation, such as highly selective catalysts of industrial importance, new insights into mechanisms of the reaction, very selective asymmetric catalysts, in situ characterization and application to organic synthesis. The views on hydroformylation which still prevail in the current textbooks have become obsolete in several respects. Therefore, it was felt timely to collect these advances in a book. The book contains a series of chapters discussing several rhodium systems arranged according to ligand type, including asymmetric ligands, a chapter on applications in organic chemistry, a chapter on modern processes and separations, and a chapter on catalyst preparation and laboratory techniques. This book concentrates on highlights, rather than a concise review mentioning all articles in just one line. The book aims at an audience of advanced students, experts in the field, and scientists from related fields. The didactic approach also makes it useful as a guide for an advanced course.

Computational Modelling of Homogeneous Catalysis is an extensive collection of recent results on a wide array of catalytic processes. The chapters are, in most cases, authored by the researchers who have performed the calculations. The book illustrates the importance of computational modelling in homogeneous catalysis by providing up-to-date reviews of its application to a variety of reactions of industrial interest, including: -olefin polymerization; -hydrogenation; -alkene/alkyne isomerization; -hydroformylation; -hydroboration; hydrosylation; -dihydroxylation; -benzannulation; -epoxidation; -N-N triple bond activation. This book facilitates understanding by experimental chemists in the field on what has already been accomplished and what can be expected from calculations in the near future. In addition, the book provides computational chemists with a first-hand knowledge on the state of the art in this exciting field.

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.

The discovery of facile catalytic alternating alkene/carbon monoxide copolymerization has significantly impacted the areas of polymer science, organometallic chemistry, and catalysis. Highly active systems that allow the directed synthesis of compounds ranging from low molecular weight esters, ketones and aldehydes to high molecular weight copolymers are now available. In addition, copolymerizations with high regio, stereo and enantioselectivity have been achieved. This title provides comprehensive coverage of all aspects of the subject. The book draws on journal and patent literature available up to the middle of 2002, as well as hitherto unpublished results. It should be of interest to academic and industrial chemists involved with transition metal catalysis, organometallic chemistry, petrochemicals, and polymeric materials. It should be suitable for specialists in the field as well as to those who wish to learn about an important and rapidly expanding area of chemistry and materials science.

"Heterocycles from Transition Metal Catalysis: Formation and Functionalization" provides a concise summary of the prominent role of late transition metal (palladium, nickel, copper) catalysed processes in the synthesis and functionalization of heterocyclic systems. It gives an introduction to catalytic transformations, an overview of the most important reaction types, and presents synthetically useful catalytic processes classified by the target system and the type of transformation.The book provides a representative selection of transition metal catalysed reactions transformations that are relevant in heterocyclic chemistry. In this way, the authors present a useful resource for members of the academic community looking for a textbook as well as industrial chemists in search of a reference book. This book will be an invaluable resource for synthetic chemists, medicinal chemists, and those more generally interested in applied catalysis.

Metal Catalysed Reactions in Ionic Liquids is the first non-edited book on the subject of metal catalyzed reactions in ionic liquids to cover the literature from its origins until early 2005. Following a general introduction to the field of biphasic/multiphasic catalysis, the book moves on to describe the synthesis, the functionalisation, and fundamental properties of ionic liquids relevant to catalysis. It then analyses the catalysed reactions according to their type, encompassing hydrogenation, hydroformylation, oxidation, C-C coupling reactions, metathesis, dimerisation, polymerisation and more. Trends, generalisations, advantages and disadvantages of ionic liquids for specific reaction types are also examined as well as specific processes such as supported ionic liquid phase catalysis, continuous processes using CO2 extraction and nanoparticle catalysis. Metal Catalysed Reactions in Ionic Liquids is of interest to those working in catalysis/green chemistry, in particular to advanced level undergraduate and  graduate students and researchers in bi- or multiphasic catalysis using ionic liquids.

This book looks at new ways of tackling the problem of separating reaction products from homogeneous catalytic solutions. The new processes involve low leaching supported catalysts, soluble supports such as polymers and dendrimers and unusual solvents such as water, fluorinated organics, ionic liquids and supercritical fluids. The advantages of the different possibilities are discussed alongside suggestions for further research that will be required for commercialisation. Unlike other books, in addition to the chemistry involved, the book looks at the process design that would be required to bring the new approaches to fruition. Comparisons are given with existing processes that have already been successfully applied and examples are given where these approaches are not suitable. The book includes: - New processes for the separation of products from solutions containing homogeneous catalysts- Catalysts on insoluble or soluble supports – fixed bed catalysts - continuous flow or ultrafiltration- Biphasic systems: water - organic, fluorous - organic, ionic liquid – organic, supercritical fluids (monophasic or biphasic with water, organic or ionic liquid)- Comparisons with current processes involving atmospheric or low temperature distillation- Consideration of Chemistry and Process Design- Advantages and disadvantages of each process exposed- Consideration of what else is need for commercialisation

Heterogeneous Enantioselective Hydrogenation: Theory and Practice reviews the development of enantioselective hydrogenation reaction catalysts. It looks at the first relatively ineffective catalysts right through to modern highly effective enantioselective catalytic systems, comparable in their efficiency to chiral metal complexes and enzymatic systems. The book begins with a summary of the first work on heterogeneous metal catalysts, which showed only the principal possibilities of enantioselective reactions. It then elaborates on metal catalysts which have enantioselectivities close to 100%. Finally, the practical utilization of chiral catalytic systems in processes of hydrogenation is described. The alpha- and beta-hydroxy carboxylic acid esters produced are precursors for manufacturing many synthones used for medicines as well as for monomers used for biodegradable polyesters, both of which have important practical applications. The volume summarizes more than 800 scientific papers in the field of enantioselective catalytic hydrogenation reactions, mainly those using heterogeneous metal catalysts. It provides detailed explanations of special techniques for the preparation of effective dissymmetric catalysts which provide highly efficient catalytic systems.

Ruthenium Oxidation Complexes explores ruthenium complexes, particularly those in higher oxidation states, which function as useful and selective organic oxidation catalysts. Particular emphasis is placed on those systems which are of industrial significance. The preparation, properties and applications of the ruthenium complexes are described, followed by a presentation of their oxidative properties and summary of the different mechanisms involved in the organic oxidations (e.g. oxidations of alcohols, alkenes, arenes and alkynes, alkanes, amines, ethers, phopshines and miscellaneous substrates). Moreover, future trends and developments in the area are discussed.This monograph is aimed at inorganic, organic, industrial and catalysis chemists, especially those who wish to carry out specific organic oxidations using catalytic methods.

Computational Modelling of Homogeneous Catalysis is an extensive collection of recent results on a wide array of catalytic processes. The chapters are, in most cases, authored by the researchers who have performed the calculations. The book illustrates the importance of computational modelling in homogeneous catalysis by providing up-to-date reviews of its application to a variety of reactions of industrial interest, including: -olefin polymerization; -hydrogenation; -alkene/alkyne isomerization; -hydroformylation; -hydroboration; hydrosylation; -dihydroxylation; -benzannulation; -epoxidation; -N-N triple bond activation. This book facilitates understanding by experimental chemists in the field on what has already been accomplished and what can be expected from calculations in the near future. In addition, the book provides computational chemists with a first-hand knowledge on the state of the art in this exciting field.

The catalytic activation of dioxygen continues to attract interest both due to its biological importance and synthetic potential. Metalloenzymes play crucial roles in metabolism by living organisms. The modelling of metalloenzymes by biomimetic metal complexes helps the search for useful oxidation catalysts and the understanding of their mechanisms of operation. Dioxygen is also the oxidant of choice in emission-free technologies aimed at minimising pollution of the environment, in line with the green chemistry requirements. This volume is devoted to recent progress in the field of catalytic oxidations using ruthenium, copper, iron, gold, cobalt and other complexes. Products and mechanistic aspects are given special emphasis throughout the book.

217 2. COPOLYMERIZATION OF PROPENE OR HIGHER I-ALKENES WITH 218 CARBON MONOXIDE 2. 1. Ligands and polymerization conditions 218 2. 2. Spiroketal formation 221 2. 3. Enantioselectivity 222 2. 4. Higher I-Alkenes 226 3. COPOLYMERIZATION OF STYRENE OR ITS DERIVATIVES WITH 226 CARBON MONOXIDE 4. COPOLYMERIZATION OF OTHER OLEANS WITH CARBON MONOXIDE 230 5. ASYMMETRIC TERPOLYMERIZATION OF MORE THAN Two KINDS OF 232 OLEFINS WITH CARBON MONOXIDE 6. POLYKETONE CONFORMATION 233 7. CONCLUSION 234 Chapter 8. Chain Propagation Mechanisms 237 Ayusman Sen 1. INTRODUCTION 237 2. PALLADIUM (II) BASED SYSTEMS 238 3. NICKEL (II) BASED SYSTEMS 256 4. RHODIUM (I) BASED SYSTEMS 257 5. CONCLUSION 261 Chapter 9. Theoretical Studies on Copolymerization of Polar Monomers 265 Peter Margl, Artur Michalak, and Tom Ziegler 1. INTRODUCTION 265 2. COPOLYMERIZATION OF CARBON MONOXIDE WITH ETHYLENE 267 2. 1. Experimental and calculated rates for the insertion processes for 267 copolymerization catalysed by Pd(II) systems. 2. 2. A more detailed look at the productive and unproductive cycles 270 in copolymerization catalysed by Pd(II) complexes. 2. 2. 1. The productive cycle 270 2. 2. 2. C2H4 misinsertion into an ethylene terminated polyketone 275 chain 2. 3. Experimental and calculated rates for the insertion processes for 277 alternating copolymerization catalyzed by Ni(II) systems 3. COPOLYMERIZATION OF OLEFINS WITH POLAR MONOMERS OTHER 280 THAN CO 3. 1. Preferred binding mode of oxygen containing monomers 282 3. 2. Preferred binding mode of nitrogen containing monomers 285 3. 3.

This volume gives a detailed account into how renewables can be transformed into value-added products via homogeneous catalysis, especially via transiton metal homogeneous catalysis. The most important catalytic reactions of oleochemicals, isoprenoids, carbohydrates, lignin, proteins and carbon dioxide are described. Special emphasis is placed on carbon-carbon linkage reactions (hydroformylations, dimerisations, telomerisations, metathesis, polymerisations etc.), hydrogenations, oxidations and other important homogeneous reactions (such as isomerisations, hydrosilylations etc.). Also, tandem reactions including isomerising hydroformylations are presented. Wherever possible, the authors have included mechanistic, kinetic, and technical aspects. The reader is therefore given a total overview of the status quo of homogeneous catalysis directed to the most important renewables.

This volume gives a detailed account into how renewables can be transformed into value-added products via homogeneous catalysis, especially via transiton metal homogeneous catalysis. The most important catalytic reactions of oleochemicals, isoprenoids, carbohydrates, lignin, proteins and carbon dioxide are described. Special emphasis is placed on carbon-carbon linkage reactions (hydroformylations, dimerisations, telomerisations, metathesis, polymerisations etc.), hydrogenations, oxidations and other important homogeneous reactions (such as isomerisations, hydrosilylations etc.). Also, tandem reactions including isomerising hydroformylations are presented. Wherever possible, the authors have included mechanistic, kinetic, and technical aspects. The reader is therefore given a total overview of the status quo of homogeneous catalysis directed to the most important renewables.

Organic chemistry is constantly concerned with effecting reactions at a particular centre in a complex molecule, and if possible with a high and predictable level of stereoselectivity. In the light of much accumulated ex­ perience within organic chemistry it is usually possible to assess the likeli­ hood of alternative reaction pathways at least qualitatively. However, well based expectations can be falsified, and the experiments directed to the synthesis of vitamin B12 which led to Woodward's recognition of orbital symmetry control in organic chemistry are an instructive example. Our limi­ tations in this respect are very much accentuated in the case of hetero­ geneous reactions, which present additional problems, and except for very well studied instances, heterogeneous catalysis has remained a relatively empirical area of chemistry. Knowledge in this area has, however, been greatly improved by the development of transition metal complexes which replicate the catalytic properties of the metals, and are effective in a homo­ geneous reaction system. This development has advanced our understanding of catalysis by making it possible to interpret reactions in strictly molecular terms. In addition, these homogeneously active complexes are frequently more selective than their heterogeneous metallic counterparts either in discriminating between different functional centres in a molecule or in of­ fering better stereoselectivity. Homogeneous catalysts have now been devised for a number of organic chemical reactions, including hydrogenation, carbonylation, polymerisa­ tion, and isomerisation and dismutation of alkenes.