Organometallic transformation, molecular

These descriptions, while helpful, are by their nature noncomprehensive and there are many exceptions if such definitions are taken too literally. The problem may be linked to the definition of organometallic chemistry as the chemistry of compounds with metal-to-carbon bonds . This immediately rules out Wilkinson s compound, RhCl(PPh3)3, for example, which is one of the most important industrial catalysts for organometallic transformations known in the field. Indeed, it is often the objectives and thought processes of the chemist undertaking the work, as much as the work itself, which determine its field. Work in modern supramolecular chemistry encompasses not just host-guest systems but also molecular devices and machines, molecular recognition, so called self-processes ... 

While the mechanism of many of the transformations described herein has not been investigated in detail, there are several examples where the reductive elimination pathway has been thoroughly evaluated via experiment and/or theory. Ultimately, a molecular-level mechanistic imderstanding of these processes should provide insights into the factors that control the relative and absolute rates of C-X bond-formation (and other fundamental organometallic transformations) at Pd. This, in turn, will serve as critical data to inform the rational design of new catalytic transformations via the Pd manifold. 

Isocyanides, also known as isonitriles or carbylamines, are characterized by a primary isocyanide (R-NC) functional group and pungent odor. According to the Hiickel, MNDO, and ab initio molecular orbital calculations, the electronic configuration of isocyanide is represented by an iminocarbene resonance hybrid (Eq. 7.1) [1]. Experimental studies have confirmed that the resonance hybrid is closely represented by the triple-bonded resonance structure [2], Electronically, isocyanides resemble that of carbon monoxide (Eq. 7.2) and recently, isocyanides have been used as substitutes for carbon monoxide in organometallic transformations [3]. 

In recent years this simple picture has been completely transformed and it is now recognized that the alkali metals have a rich and extremely varied coordination chemistry which frequently transcends even that of the transition metals. The efflorescence is due to several factors such as the emerging molecular chemistry of lithium in particular, the imaginative use of bulky ligands, the burgeoning numbers of metal amides, alkoxides, enolates and organometallic compounds, and the exploitation of multidentate... 

Overall, this study shows that, like in molecular organometallic chemistry, the chemistry on metal surfaces follows similar elementary steps, and that it is possible to have a molecular understanding of catalytic phenomenon such as paraffin transformations on metal particles. 

The first chemical transformations carried out with Cjq were reductions. After the pronounced electrophilicity of the fullerenes was recognized, electron transfer reactions with electropositive metals, organometallic compounds, strong organic donor molecules as well as electrochemical and photochemical reductions have been used to prepare fulleride salts respectively fulleride anions. Functionalized fulleride anions and salts have been mostly prepared by reactions with carbanions or by removing the proton from hydrofullerenes. Some of these systems, either functionalized or derived from pristine Cjq, exhibit extraordinary solid-state properties such as superconductivity and molecular ferromagnetism. Fullerides are promising candidates for nonlinear optical materials and may be used for enhanced photoluminescence material. 

One major reason for the great interest in the processes of thin metal-containing films is that reactions on the surface of small metal clusters can be studied. Indeed, prior to the development of thin-film chemistry, reactions of similar particles were studied only in the gas phase at rather high temperatures. Under these conditions, most of the primary products are unstable and decompose in the course of further reaction, which is non-selective. As a result, the information obtained on the routes and mechanisms of reactions of disperse metals appears to be scarce, while the use of such reactions in synthesis is inexpedient. Conversely, low-temperature reactions in the films of co-condensates are very promising from the standpoint of determining the detailed reaction mechanism, as well as for synthesis of previously unknown complexes and organometallic compounds. It is important that atoms of only a few metals react with organic compounds immediately at the instant of their contact on the cooled substrate. Rather often, atoms and/or small (molecular) clusters are first stabilized in the film, and then their transformations are observed. 

Dembitsky, V. M. Srebnik, M. Organometallics Boron Compounds, (D.S. Matteson, D. Kaufmann, Eds.) Science of Synthesis, Houben-Weyl Methods of Molecular Transformation, Vol. 6, Chapter 28, Georg Thieme Verlag, Stuttgart, Germany, 2004. In press. 

Few organic transformations add as much molecular complexity in one step as the Pauson-Khand reaction. This reaction is one of the best examples of how organometallic chemistry is useful in modern organic synthesis, and can serve as a key tool for the synthesis of natural products, in this case those possessing cyclopentane units. The limited scope, low yields and lack of efficient catalytic procedures were serious drawbacks in the past that have been... 

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