In alkyl coupling, an alkyl group from this reagent displaces a halide on the other reactant, forming a new carbon-carbon bond.  
The coupling reaction they enable is extremely versatile, as it can be carried out on aryl, vinyl, and alkyl halides.  In alkyl coupling, an alkyl group from this reagent displaces a halide on the other reactant, forming a new carbon-carbon bond.  These reagents will react with bromides or iodides, but not fluorides and rarely chlorides.  They are prepared by reacting cuprous iodide with an alkyl lithium.  FTP, identify this type of reagent with the general formula of R2CuLi, whose chemistry is similar to that of Grignard reagents.
The coupling reaction they enable is extremely versatile, as it can be carried out on aryl, vinyl, and alkyl halides.  
Gilman reagent