Lithium diarylcuprates

Lithium diarylcuprates are prepared m the same way as lithium dialkylcuprates and undergo comparable reactions with primary alkyl halides... 

Discrete diarylcuprate anions have been observed in crystals in which the lithium cation is complexed by crown ethers.5 Both tetrahedral Ph4Cu4 and [Ph2Cu] units have been observed in complex cuprates containing (CH3)2S as a ligand. [Ph3Cu]2- units have also been observed as parts of larger aggregates.6... 

A compound containing carbon-copper bonds, commonly of formula R2CuLi (Gilman reagent). The lithium dialkylcuprate (or diarylcuprate or divinylcuprate) displaces an organohalogen bond to form a new C—C. (p. 791)... 

Lithium-cuprate complexes obtained by the reaction of Cu(I) iodide and the corresponding aryllithium were also successfully applied in the synthesis of unsymmetrical biaryls [23]. An alternative strategy involves the low temperature oxidative coupling of higher order mixed diarylcuprates [24]. The classical Ullmann reaction can be accelerated by using, instead of copper... 

Lithium dialkylcuprates and diarylcuprates (R2CuLi and Ar2CuLi) are prepared by the reaction of a copper(I) salt with two equivalents of the corresponding organolithium reagent and undergo cross-coupling with primary alkyl halides and aryl and vinylic halides. 

---