The design, -synthesis, and selective pyrolytic conversion of organo metallic precursdrs to materials of high purity or specific morphology (for electronic or optical applications), high strength and/or high-temperature stability (for structural or refractory applications) represents a poten tial area of extreme growth at the overlap of chemistry and materials science (materials chemistry). Research in this area is likely to have considerable impact at both the academic and societal levels because it will require development of scientific expertise in areas currently not well understood. Examples include: (1) The thermodynamics of molecular rearrangements in organometallic molecules at temperatures above 200°C; (2) The electronic properties of amorphous ceramic materials; (3) The phys icochemical properties of ceramic molecular composites; and (4) The optical properties of multicomponent glasses made by sol-gel processing. The opportunity to establish the scientific principles needed to pursue useful research goals in "materials chemistry" requires communica tion between chemists, ceramists, metallurgists, and physicists. To date, there have been few opportunities to create an environment where such communication might occur. The objective of this NATO Advanced Research Workshop was to promote discussions between experts in the varibus disci plines aligned with "materials chemistry. " These discussions were intended to identify the scope and potential rewards of research efforts in the development of: Custom-designed precursors to common and exotic materials, methods of selectively transforming these precursors in high yield to the desired material, and methods of characterizing the final products.

When one considers the overall representation of frontier orbital filling of hexacoordinate (Oh) and tetracoordinate (Td) inorganic and organo metallic complexes, it clearly appears that out of 26 cases covering both high spin and low spin situations, 21 represent paramagnetic species (K. Purcell, J. Kotz, "Inorganic Chemistry", Saunders, 1977, p561). This would suggest that, if there is a part in chemistry to illustrate the reactivity of radical species, this part certainly is inorganic organometallic chemistry. In contrast with these expectations, and whereas the standard Organic Chemistry textbook (J. March ,"Advanced Organic Chemistry", J. Wiley, N. Y. , 1985) has a specific chapter devoted to free radical reactivity, neither the inorganic standard (FA Cotton, G. Wilkinson, "Advanced Inorganic Chemistry", Wiley, 1988), nor the Organometallic one (J. P. Collman, L. S. Hegedus, J. R. Norton, R. G. Finke, "Principles and Applications of Organotransition Metal Chemistry", University Science Books Mill Valley C. A. , 1987) possess such a specific chapter. The balance is partly restored because the two last cited books have a more comprehensive treatment of electron transfer phenomena. These comparisons show unambiguously that the importance of paramagnetic species in chemical reactivity still lacks a consistent treatment transcending the artificial barriers between branches of Chemistry. This book, which brings together experimental facts and concepts originating from organometallic and organic reactivities, is a step in the direction of bridging this gap. The unifying thread which connects the 35 chapters throughout this book is Activation/Selectivity and Catalysis by means of radical chemistry.

The objective of this workshop was to identify the scope and potential rewards of research efforts in the development of methods of transforming organometallic compounds into useful materials. This report covers the presentations in chemical vapor deposition, sol-gel processing, and preceramic polymers. Keywords: Ceramic materials; Ceramic coatings; Metal coatings; Metallic crystals; Organic coatings.

Surface organometallic chemistry is a new field bringing together researchers from organometallic, inorganic, and surface chemistry and catalysis. Topics ranging from reaction mechanisms to catalyst preparation are considered from a molecular basis, according to which the "active site" on a catalyst surface has a supra-molecular character. This. the first book on the subject, is the outcome of a NATO Workshop held in Le Rouret. France, in May. 1986. It is our hope that the following chapters and the concluding summary of recommendations for research may help to provide a definition of surface organometallic chemistry. Besides catalysis. the central theme of the Workshop, four main topics are considered: 1) Reactions of organometallics with surfaces of metal oxides, metals. and zeolites; 2) Molecular models of surfaces, metal oxides, and metals; 3) Molecular approaches to the mechanisms of surface reactions; 4) Synthesis and modification of zeolites and related microporous solids. Most surface organometallic chemistry has been carried out on amorphous high-surf ace-area metal oxides such as silica. alumina. magnesia, and titania. The first chapter. contributed by KNOZINGER. gives a short summary of the structure and reactivity of metal oxide surfaces. Most of our understanding of these surfaces is based on acid base and redox chemistry; this chemistry has developed from X-ray and spectroscopic data, and much has been inferred from the structures and reactivities of adsorbed organic probe molecules. There are major opportunities for extending this understanding by use of well-defined (single crystal) oxide surfaces and organometallic probe molecules.