Organolithium compounds with metal halides

Ge—metal bonds can be built in analogy as described for Ge—C bonds by the reaction of organolithium compounds with metal halides. With trans-dichlorobis(triethylphosphine)platinum(II), new germyl transition metal complexes were synthesized (equation 36)41. 

When CHsLi or n-BuLi is used in halogen-metal exchange, a rather electrophilic MeX or -BuX is obtained as a by-product. The alkyl halide can undergo Sn2 substitution with the organolithium compound as nucleophile to give the nucleophilic aromatic substitution product. However, Sn2 reactions of organolithium compounds with alkyl halides are rather... 

Organolithium reagents (Section 14 3) Lithi um metal reacts with organic halides to pro duce organolithium compounds The organic halide may be alkyl alkenyl or aryl Iodides react most and fluorides least readily bro mides are used most often Suitable solvents include hexane diethyl ether and tetrahy drofuran... 

Further, elemental phosphorus can be converted by Grignard reagents or organolithium compounds into metal phosphides which afford primary phosphines on hydrolysis phenylphosphine was obtained in this way in yields of up to 40% from phenyllithium and white phosphorus.214 In some circumstances cyclophosphines are formed on reaction of alkyl halides with the phosphide solutions obtained from elemental phosphorus.215... 

The direct reaction of an organic halide with an alkali metal is one of the most important methods for synthesizing organolithium compounds. The reaction of two equivalents of the alkali metal with one equivalent of the organohalide produces the organoalkali metal compound and metal halide... 

Organolithium compounds are one of the widely used reagents in organic synthesis. Another use of organolithium reagents is in the preparation of various organometallic compounds, usually by reaction with metal halides. Therefore, the preparation of organolithium is important even in r-bowl chemistry. 

As the other synthetic method of organoruthenium compounds, the reaction of organolithium compounds or Grignard reagents with metal halides, which is the representative synthetic method of the main group organometallic compounds, is also available [25—28]. For example, organoalkali metal compounds react easily with ruthenium halides to form condensation products as shown in eq. (16.17) [25]. 

Many organic halides do not react satisfactorily with lithium to form RLi ecMnpounds or with metallic magnesium to form Grignard reagents. The desired organolithium compound can often be prepared by a halogen-metal interconversion reaction ... 

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

Organolithium compounds are sometimes prepared in hydrocarbon solvents such as pentane and hexane, but nonnally diethyl ether is used. It is especially important that the solvent be anhydrous. Even trace amounts of water or alcohols react with lithium to form insoluble lithium hydroxide or lithium alkoxides that coat the surface of the metal and prevent it from reacting with the alkyl halide. Furthennore, organolithium reagents are strong bases and react rapidly with even weak proton sources to fonn hydrocarbons. We shall discuss this property of organolithium reagents in Section 14.5. 

Organolithium compounds can readily be prepared from metallic Li and this is one of the major uses of the metal. Because of the great reactivity both of the reactants and the products, air and moisture must be rigorously excluded by use of an inert atmosphere. Lithium can be reacted directly with alkyl halides in light petroleum, cyclohexane, benzene or ether, the chlorides generally being preferred ... 

Next to the formation of Grignard reagents, the most important application of this reaction is the conversion of alkyl and aryl halides to organolithium compounds, but it has also been carried out with many other metals, (e.g., Na, Be, Zn, Hg, As, Sb, and Sn). With sodium, the Wurtz reaction (10-93) is an important side reaction. In some cases, where the reaction between a halide and a metal is too slow, an alloy of the metal with potassium or sodium can be used instead. The most important example is the preparation of tetraethyl lead from ethyl bromide and a Pb—Na alloy. 

Organolithium compounds are often prepared by the reduction of organic halide with lithium metal. 

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