Organolithium chemistry

Organolithium chemistry is the science of organotitanium compounds describing their physical properties, synthesis, and reactions. Organolithium compounds in organometallic chemistry contain carbon-lithium chemical bonds. A major subset and perhaps the most used organolithium compounds are organolithium reagents, such as butyllithium^[1]

Classification

Alkyl and aryl monolithium compounds

Various depictions of the methyl lithium tetramer. Colour code: Li- purple C- black H- white

Alkyl and aryl monolithium are illustrated by their simplest members, methyl lithium and phenyl lithium. These useful reagents have complicated structures owing to the tendency of the C-Li unit to aggregate, forming clusters.^[2] These compounds are prepared by metal-halogen exchange, which entails stirring solutions of the alkyl halide with lithium metal:

CH₃Br + Li → CH₃Li + LiBr

Lithium-reduced polycyclic aromatics

A solution of lithium naphthenide in tetrahydrofuran

Naphthalene, anthracene, and related polycyclic aromatic compounds are reduced by lithium to give Li⁺ salts of their radical anions:^[3]

C₁₀H₈ + Li → Li⁺C₁₀H−8

Lithium naphthalene (Li⁺[C₁₀H₈]⁻) is used as a reductant in the synthesis of organic, organometallic, and inorganic chemistry.

Dilithio compounds

These compounds, which have two C-Li bonds can be classified into two distinct groups. Simplest but rare is dilithiomethanide (CH₂Li₂) and its many derivatives.^[4] Some derivatives have even been characterized by X-ray crystallography.^[5]

The more common dilithiated organic compounds the Li atoms are bound to separate carbon atoms. 1,4-dilithiobutane (LiCH₂CH₂CH₂CH₂Li) would be an example.

Dilithioacetylide (Li₂C₂, again is not a salt, but adopts a distorted anti-fluorite crystal structure, similar to that of rubidium peroxide (Rb₂O₂).^[6]

Tetralithio compounds

Tetralithiomethane has attracted attention mainly for theoretical reasons. Its structure remains uncertain, but some speculation posited planar carbon.