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Über dieses Buch

More and more possible applications of organometallic compounds in organic synthesis have been uncovered and a growing number of scientists are attracted to this area of research. This book presents an state-of-the-art account of the successful application of main- and transition metal mediated syntheses. It will stimulate new ideas and initiate further research in all areas of this fascinating chemistry.

Inhaltsverzeichnis

Frontmatter

Organometallic Reactivity and Applied Quantum Chemistry — Some Aspects of CH-Activation

Abstract
The rapid development of computational facilities and of increasingly efficient, highly sophisticated quantum chemical methodologies and programs has certainly reached a point now, where ab initio calculations for small molecules, composed of light atoms, appear to provide numerically accurate predictions of structures and energies, comparable or even superior to experimental data. The ultimate goal of molecular quantum chemistry, the reliable a priori prediction of geometry, physical properties and in particular of chemical reactivity in a quantitative sense, based upon “first principles” alone, is, however, still quite far away for organometallic species involving transition metals or heavy main group elements. Even today’s best “state of the art” electronic structure calculations for such systems only represent rather crude approximations to the “truth”, at least as far as molecules of realistic size and of actual relevance to experimental chemists are concerned. On the other hand transition metal organometallics have been playing and obviously will continue to play a vital and important role in synthetic chemistry. This is not only true as far as large scale industrial production through homogeneous (or heterogeneous) catalysis is concerned, but also in the field of stoichiometric, highly selective multistep transformations leading to high value, small scale fine chemicals, or in various other areas of present or future interest to academic and industrial research (Parshall 1987).
Peter Hofmann

The Functionalization of Hydrocarbons by Transition Metal Phosphine Complexes: Aspects and Prospects

Abstract
The intermolecular activation of notoriously unreactive carbon-hydrogen bonds by transition metal complexes continues to present an important challenge to organometallic chemistry, since hydrocarbons are perhaps the most attractive sources of more complex molecules.
L. Dahlenburg

Novel Metalla-Heterocycles Formed By [3+2], [2+2], and [2+3] Cycloaddition Reactions of Cyclopentadienyl Cobalt and Rhodium Complexes

Abstract
Following the discovery that the cyclopentadienyl cobalt bis(phosphine) complexes C5H5Co(PR3)2 are strong metal bases [1], we became interested to find out whether also derivatives of the general composition C5H5Co(PR3)2, in which L is a n-acceptor ligand, despite of the reduced electron density at the metal atom still show the same type of behavior. After the carbonyl compound C5H5Co(PMe3)C0 had been investigated [2], the isocyanide cobalt complexes C5H5Co(PMe3)CNR were prepared and found not only to be good nucleophiles but also useful starting materials for the synthesis of four- and five-membered metalla-heterocycles.
H. Werner

Ketenimine Complexes as Building Blocks for N-Heterocyclic and Carbocyclic Compounds

Abstract
Carbene-metal complexes of Cr, Mo, W. Fe and other metals are stable and easily prepared compounds [1]. They can be used in various ways as starting materials for organic syntheses [2].
Rudolf Aumann

Metal Carbenes in Cycloaddition Reactions

Abstract
Two decades after E.O. Fischer’s first report of an isolated transition metal carbene complex (Fischer and Maasbol, 1964) this class of compounds represents a well-established research area in organometallic chemistry. We are now able to synthesize carbene complexes of nearly all transition metals. We can control the oxidation state, the ligand sphere and the stereochemistry of the metal as well as the reactivity of the metal to carbene bond (Dötz et al., 1983a). The original Fischer-type complexes contain a low-valent metal center connected to an electrophilic carbene carbon atom which results in a carbonyl-like reactivity. These properties are exactly reversed in compounds which have been discovered by R.R. Schrock ten years later which exhibit an ylid-like chemical behavior (Schrock, 1979).
Karl Heinz Dötz

Ketenyl Complexes in the Organic Synthesis

Abstract
Dicarbonyl(n5-cyclopentadienyl) carbyne complexes of molybdenum and tungsten (Fischer 1976, Kreißl 1979) react with an equimolar amount of strong bases such as phosphines via an intramolecular carbon-carbon coupling to yield n2 ketenyl complexes (Kreißl 1977, 1979) and trimethylphosphine-substituted carbyne complexes. The n2-ketenyl compounds can be isolated as stable, deeply colored crystals
F. R. Kreißl

Organorhenium Oxides

Abstract
The selective formation of carbon-carbon, carbon-hydrogen, carbon-oxygen, and carbon-nitrogen bonds at transition metal sites has long been one of the major topics in the field of applied chemistry, with the final goal exceeding the stage of stoichiometric reactions towards catalysis. In this context it is one of the organometallic chemist’s great challenges to construct compounds that serve as models for either homogeneous or heterogeneous catalysts. Olefin metathesis (Mo, W, Re), hydroformylation (Co, Rh), the MONSANTO acetic acid process (Rh), and the WACKER-HOECHST acetaldehyde synthesis (Pd) present well-known examples to demonstrate the importance of organometallic model systems for a better understanding of catalytic mechanisms. This is still true even when safe conclusions for heterogeneous processes cannot be drawn from stoichiometric reactions carried out at soluble (homogeneous) species.
Wolfgang A. Herrmann

Carbene Complex Syntheses with Group 4 Metallocene Reagents

Abstract
Since their discovery in the early sixties, transition metal carbene complexes have developed into reagents of rapidly increasing importance for the transformation of organic substrates (Dotz 1983). Examples of this class of compounds serve as the reactive intermediates in olefin disproportionation (“olefin metathesis”) and alkylidene transfer reactions. They may also play an important role in many alkene and alkyne oligomerizations. In addition, transition metal carbene complexes have turned out to be interesting stoichiometric reagents in organic synthesis. Nucleophilic “Schrock-type” carbene complexes of the early transition elements have found specific uses as selective alkylidene donors in “Wittig-type” carbonyl olefination reactions. However, the most remarkable synthetic developments have been achieved with heteroatom stabilized electrophilic “Fischer-type” carbene complexes as reagents in organic synthesis (Brown 1980).
Gerhard Erker

The Behaviour of a Dialuminoxane and Distannoxanes towards Organic Molecules

Abstract
The concept of the combined acid-base attack is exemplified by the behaviour of organoaluminium amides towards trisubstituted oxiranes, which are converted into allylic alcohols. The coordination of the reagent on the oxirane oxygen occurs in a fast equilibrium, whereas the nitrogen lone pair thus activated abstracts a proton from the ∝-carbon on the same side as the ring hydrogen, and the nucleophilic attack is rate-and product-determining. Furthermore, the above concept is extended to the reaction of neryl diethyl phosphate with (iBu2Al) 2O, which involves the intermediary ion-pair containing neryl cation and phosphate-dialuminoxane complex anion. The extensively delocalized negative charge in the anion complex leaves a nearly naked neryl carbocation behind, the cyclization of which is followed by deprotonation. The latter stage of nucleophilic attack is again the real rate and product-determining step. The concept of the combined acid-base attack is exemplified by the behaviour of organoaluminium amides towards trisubstituted oxiranes, which are converted into allylic alcohols. The coordination of the reagent on the oxirane oxygen occurs in a fast equilibrium, whereas the nitrogen lone pair thus activated abstracts a proton from the oc-carbon on the same side as the ring hydrogen, and the nucleophilic attack is rate-and product-determining. Furthermore, the above concept is extended to the reaction of neryl diethyl phosphate with (iBu2Al)20, which involves the intermediary ion-pair containing neryl cation and phosphate-dialuminoxane complex anion. The extensively delocalized negative charge in the anion complex leaves a nearly naked neryl carbocation behind, the cyclization of which is followed by deprotonation. The latter stage of nucleophilic attack is again the real rate- and product-determining step.
Hitosi Nozaki, Junzo Otera

Olefin Insertion into Organyl Metal Bonds

Abstract
The insertion of an olefinic C=C bond into an organometallic metal-carbon bond is of potential interest as a preparative route to new organometallics and as result of C-C coupling reactions to organic compounds. In addition, it is valuable from a mechanistic point of view to understand more about the key step in the metal catalyzed di-, oligo- and polymerization of olefins. In the “Aufbaureaktion” (Ziegler 1952,1960) triethylaluminium reacts with ethylene by a stepwise insertion of ethylene molecules into the Al-C bonds to give a mixture of aluminium compounds with alkyl groups of the type -(CH2CH2)nEt. This mixture is statistically controlled because triethylaluminium and all intermediates (n =1 to n) during this reaction have similar reactivities towards ethylene1. If the M-R bond at the beginning is much more reactive than the M-C bond of the first insertion product, the reaction would terminate after the first step (Scheme 1).
Herbert Lehmkuhl

Oxidation Processes and Oxygen Activation Involving Palladium Complexes

Abstract
Oxidation is a fundamental process in chemistry (Sheldon and Kochi 1981). When transition metal complexes are involved “Fig. 1” different types of catalytic or stoichiometric reactions can take place. Redox processes occuring on the metallic center are among the most familiar to chemists interested in organic synthesis, particularly when the metal is palladium, (Trost 1977, 1980; Heck 1979;Akermark 1982 ? Bäckvall 1983; Tsuji 1980, 1984, 1986 ? Hegedus 1983, 1984; Yamamoto 1986).
Bernard Waegell

Cyclopentenone Formation from Alkyne-Cobalt Complexes

Abstract
Virtually all alkynes react smoothly and under mild conditions with octacarbonyldicobalt to yield complexes of the type (1). When treated with alkenes such complexes react to give cyclopentenone derivatives (2), a reaction which we call “Khand reaction” after my late coworker Dr. I. U. Khand, who not only first observed this transformation, but also subjected it to systematic study.
P. L. Pauson

Some Uses of Metal Carbonyl Complexes in Organic Synthesis

Abstract
A survey is presented of applications of various Tricarbonyl iron and Methyl cyclopentadienyl dicarbonyl (allene) manganese complexes as intermediates for organic synthesis.
Michel Franck-Neumann

Selective Reactions on Arene Chromium Complexes

Abstract
Arene complexes of transition metals figure prominently in the field of organometallic chemistry (Collman, 1987; Watts, 1982). This, in part, is due to the rich structural, stereochemical and electronic features of arene metal bonds (Muetterties, 1982). It is also due to the ability of coordinated arenes to undergo new and highly selective reactions under mild conditions. In preparative organic chemistry, arene transformations via complexation complement classic arene chemistry such as aromatic electrophilic substitution (Collman, 1987) (Watts, 1982; Muetterties, 1982; Braun, 1985). Particularly useful in this respect are those arene complexes in which the arene is bound to electron withdrawing fragments.
E. P. Kündig, N. P. Do Thi, P. Paglia, D. P. Simmons, S. Spichiger, E. Wenger

A Zinc Mediated Route from α-Imino Esters to β-Lactams

Abstract
In the course of our studies on the coordination behavior of 1,4-dihetero-1,3-butadienes towards Li-, Cu-, Zn-, A1-, and Sn-organometallic compounds, it became obvious that in many cases these substituted 1,4-dihetero-1,3-butadiene molecules (Table 1) are converted selectively into organic compounds containing either two equivalent or two different α-positioned heteroatoms. Up still now, little effort appears to have been put into exploring this particular synthetic route.
Gerard Van Koten

Use of Dinuclear Templates to Perform the Hydroformylation Reaction

Abstract
The hydroformylation of alkene into the corresponding linear and branched aldehyde is a very important reaction (Cornils 1980, Marko 1974 and Tkatchenko 1982)
Ph. Kalck
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