Preparation organometallic compounds

The organometallic compounds prepared from alkali metal derivatives of metal carbonyls include compounds in which a transition metal of a metal carbonyl residue is cr-bonded to another atom such as a carbon atom in an alkyl, acyl, aryl, or perfluoroalkyl group, to the heavier congeners of carbon —silicon, germanium, tin, and lead—to mercury and gold which form unusually stable compounds, and even to other transition metals. The preparation and properties of all of these classes of compounds will be considered and, for the sake of completeness, a few related compounds prepared by routes other than those involving anionic metal carbonyl derivatives will be discussed. 

D yakonov VA (2010) In Chin HF (ed) Organometallic compounds preparation, structure and properties. Nova Science, New York, p 425... 

Formation of ketones. Ketones can be prepared by the carbonylation of halides and pseudo-halides in the presence of various organometallic compounds of Zn, B, Al, Sn, Si, and Hg, and other carbon nucleophiles, which attack acylpalladium intermediates (transmetallation and reductive elimination). 

The properties of organometallic compounds are much different from those of the other classes we have studied to this point Most important many organometallic com pounds are powerful sources of nucleophilic carbon something that makes them espe cially valuable to the synthetic organic chemist For example the preparation of alkynes by the reaction of sodium acetylide with alkyl halides (Section 9 6) depends on the presence of a negatively charged nucleophilic carbon m acetylide ion... 

Organohthium and organomagnesium compounds are stable species when prepared m suitable solvents such as diethyl ether They are strongly basic however and react instantly with proton donors even as weakly acidic as water and alcohols A proton is transferred from the hydroxyl group to the negatively polarized carbon of the organometallic compound to form a hydrocarbon... 

The preparation and structure determination of ferrocene marked the beginning of metallocene chemistry Metallocenes are organometallic compounds that bear cyclo pentadiemde ligands A large number are known even some m which uranium is the metal Metallocenes are not only stucturally interesting but many of them have useful applications as catalysts for industrial processes Zirconium based metallocenes for example are the most widely used catalysts for Ziegler-Natta polymerization of alkenes We 11 have more to say about them m Section 14 15... 

Grignard reagents react with ethylene oxide to yield primary alcohols containing two more carbon atoms than the alkyl halide from which the organometallic compound was prepared... 

Before we describe the applications of organometallic reagents to organic synthesis, let us examine their preparation. Organolithium compounds and other Group I organometallic compounds are prepared by the reaction of an alkyl halide with the appropriate metal. 

Organolithium and organomagnesium compounds find their- chief use in the preparation of alcohols by reaction with aldehydes and ketones. Before discussing these reactions, let us first exanine the reactions of these organometallic compounds with proton donors. 

It is notable that the preparation of alkyl and aryl derivatives from Pb starting materials always results in Pb organometallic compounds. The only well-defined examples of Ptf ... 

Grignard reagents are a very important class of organometallic compounds. For their preparation an alkyl halide or aryl halide 5 is reacted with magnesium metal. The formation of the organometallic species takes place at the metal surface by transfer of an electron from magnesium to a halide molecule, an alkyl or aryl radical species 6 respectively is formed. Whether the intermediate radical species stays adsorbed at the metal surface (the A-modelf, or desorbs into solution (the D-model), still is in debate ... 

Compounds prepared from naturally occurring nucleosides are of course more closely related to genetic material and may have a better chance of interacting with infected cells. Mercu-ration of the 2 -dcoxyuridine 113 leads to the organometallic derivative 114 reaction of that with ethylene in the presence dilithio palladium tetrachloride gives the alkylation product 115 this is reduced catalytically in situ. There is thus obtained the antiviral agent edoxudine (116) [25]. 

Many other kinds of organometallic compounds can be prepared in a manner similar to that of Grignard reagents. For instance, alkyllithium reagents, RLi, can be prepared by the reaction of an alkyl halide with lithium metal. Alkyllithiums are both nucleophiles and strong bases, and their chemistry is similar in many respects to that of alkylmagnesium halides. 

Recently some information became available on a new type of highly active one-component ethylene polymerization catalyst. This catalyst is prepared by supporting organometallic compounds of transition metals containing different types of organic ligands [e.g. benzyl compounds of titanium and zirconium 9a, 132), 7r-allyl compounds of various transition metals 8, 9a, 133), 7r-arene 134, 185) and 71-cyclopentadienyl 9, 136) complexes of chromium]. 

The data obtained up to the present time show that the method of catalyst preparation by the reaction of organometallic compounds with surface reactive groups may be applied to generate both isolated ions of transition metals (in various valent states) or superfine metal particles on the surface of the support. 

Aylett, B. J., and Tannahill, A. A., Chemical Vapour Deposition of Metal Silicides from Organometallic Compounds with Silicon-Metal Bonds, SIRA Int. Seminar on Thin Film Preparation and Processing Technolgy, Brighton, UK (March 1985)... 

A quite surprising development, even to experienced workers in elemental-fluorine chemistry, has been the synthesis of trifluoromethyl organometallic compounds by direct fluorination of metal alkyls (25). Even more surprising is the fact that, for certain metal and metalloid systems, such as the reaction of elemental fluorine with tetramethyl-germane, this t5rpe of low-temperature synthesis is a practical method 26) for the laboratory preparation of the perfluoro analog. 

Using this technique, it is extremely easy to prepare almost all of the trifluoromethyl organometallic compounds that have been discussed... 

The first trifluorosilyl "organometallic compound, bis(trifluorosi-lyDmercury, has been prepared by using the new, metal-vapor technique (35). 

---