Chemistry organometallic

This report provides new routes to transition metal propargyl/allenyl chemistry, an area of current interest in organometallic chemistry. 

In similar reactions, iridium(I) and rhodium(I) complexes react with the vinyliodonium salt I(CH = CH2)Ph][OTf] to form octahedral complexes 103 and 104.2 2 

Some cluster compounds contain no organic ligands. 

The first organometallic compound to be reported was synthesized in 1827 by Zeise, who obtained yellow needle-like crystals after refluxing a mixture of PtCl4 and PtCl2 in ethanol, followed by addition of KCl solution. Zeise correctly asserted that this yellow product, subsequently dubbed Zeise s salt, contained an ethylene group. This assertion was questioned by other chemists, most notably Liebig, and it was not verified conclusively 

The first compound to be synthesized that contained carbon monoxide as a ligand was another platinum chloride complex, reported in 1867. In 1890, Mond reported the preparation of Ni(CO 4, a compound that became commercially useful for the purification of nickel. Other metal CO (carbonyl) complexes were soon obtained. 

The product was surprisingly stable it could be sublimed in air without decomposing and was resistant to catalytic hydrogenation and Diels-Alder reactions. In 1956, X-ray 

In main group chemistry, we have encountered the octet rule, in which electronic structures can be rationalized on the basis of a valence shell requirement of 8 electrons. Similarly, in organometallic chemistry, the electronic structures of many compounds are based on a total valence electron count of 18 on the central metal atom. As with the octet rule, there are many exceptions to the 18-electron rule, but the rule nevertheless provides useful guidelines to the chemistry of many organometallic complexes, especially those containing strong 7T-acceptor ligands. 

A characteristic of metal atoms bonded to organic ligands, especially CO, is that they often exhibit the capability to form covalent bonds to other metal atoms to form cluster compounds. These clusters may contain only two or three metal atoms or as many as several dozen there is no limit to their size or variety. They may contain single, 

Staggered rings Eclipsed rings Skew rings 

Carbene (alkylidene) Carbyne (alkylidyne) Cyclopropenyl (cycto-CgHj) 

The corresponding formulas and names are designated according to this system as follows  

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One of the characteristic properties of organometallic reagents 1 is that the carbon atom serves as a nucleophile in chemical reactions. In contrast, when a carbon atom is bonded to more electronegative elements such as the halogen atom in the alkyl halide 2 (X = Cl, Br, or I) or oxygen atom in the carbonyl compound 3, it is electron-deficient or Lewis acidic and possesses a partial positive charge. Such carbon atoms then serve as electrophiles in chemical reactions. 

Because of their nucleophilic character, organometallic compounds are widely utilized as reagents in reactions that produce new carbon-carbon bonds. For example, two typical reactions of organometallic reagents 1 with carbon electrophiles such as alkyl halides 2 and carbonyl compounds 3 are illustrated by the general transformations shown in Equations 19.1 and 19.2. In each of these reactions, the nucleophilic carbon atom of one reactant becomes attached to the electrophilic carbon atom of the other reactant with the resulting formation of a new carbon-carbon bond. Thus, like many bond-forming processes, these reactions may be viewed in the simple context of combinations of Lewis bases with Lewis acids. 

Reactions of Organic Halides with Magnesium Metal 

Grignard reagents, R-MgX or Ar-MgX, are typically prepared by the reaction of an alkyl halide, R-X, or an aryl halide, Ar-X, with magnesium metal in an anhydrous ethereal solvent (Eq. 19.3) the organometallic reagent dissolves as it is formed. You may note that carbon is transformed from an electrophilic center in the starting material R-X or Ar-X into a nucleophilic center in the product R-MgX or Ar-MgX in this process. 

Tetraethyl- and tetramethyl-lead are removed from internal combustion engines by scavenging, i.e., a reaction with halogenated hydrocarbon gasoline ad- 

Compound Formula Molecular weight Solubility, g/100 ml Other 

Abbreviations a = acid al = alcohol alk = alkali d = decomposes expl = explodes glyc=glycol i = insoluble s = soluble nd = no data 

An excellent survey of the chemical and physical properties and the preparation of organolead compounds has been prepared by Shapiro and Frey [62]. 

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Gmelin Handbook of Inorganic and Organometallic Chemistry. This provides data similai to Bedsteia foi both inoiganic and ... 

Similar treatment of the organometaUic chemistry of the PGMs are found ia G. Wilkinson, E. Gordon, A. Stone, and E. W. Abel, eds.. Comprehensive Organometallic Chemistry Pergamon Press, Oxford, U.K., 1982. 

Whereas CP2MX2 compounds are ubiquitous ia early transition-metal organometallic chemistry, the thorium analogues are rather unstable. 

P. C. Wailes, R. S. P. Coutts, and H. Weigold, Organometallic Chemistry of Titanium, Eirconium, andMafnium, Academic Press, Inc., New York, 1974. 

R. Tiitzet, Abstracts opPapers opthe 3rd International Symposium on Organometallic Chemistry, Munich, Gemiany, Aug. 28-Sept. 1, 1967, p. 196. 

Organometallic Chemistry. Only a few organocalcium compounds have been reported. Alkyl calcium haUdes have been prepared by reaction of the hahdes and calcium ia tetrahydrofuran (17). 

As a result of the systematic application of coordination-chemistry principles, dozens of previously unsuspected stnicture types have been synthesized in which polyhedral boranes or their anions can be considered to act as ligands which donate electron density to metal centres, thereby forming novel metallaboranc elusters, ". Some 40 metals have been found to act as acceptors in this way (see also p. 178). The ideas have been particularly helpful m emphasizing the close interconnection between several previously separated branches of chemistry, notably boron hydride clu.ster chemistry, metallaboranc and metallacarbaborane chemistry (pp. 189-95). organometallic chemistry and metal-metal cluster chemistry. All are now seen to be parts of a coherent whole. 

Structure of ferrocene elucidated organometallic chemistry burgeons Nobel Prize awarded jointly to E. O. Fischer and G. Wilkinson 1973,... 

R. H. Crabtree The Organometallic Chemistry of the Transition Metals, Wiley, New York, 1988, 440 pp. 

The steady trend towards increasing stability of rather than M compounds in the sequence Ge, Sn, Pb is an example of the so-called inert-pair effect which is well established for the heavier post-transition metals. The discussion on p. 226 is relevant here. A notable exception is the organometallic chemistry of Sn and Pb which is almost entirely confined to the state... 

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