;Magnesium–halogen exchange
Grignard reagents can be prepared by treating a preformed Grignard reagent with an organic halide. This method offers the advantage that the Mg transfer tolerates many functional groups.  A typical reaction involves isopropylmagnesium chloride and aryl bromide or iodides:
: i-PrMgCl  +  ArCl  →  i-PrCl  +  ArMgCl
Magnesium ate complexes metalate aryl halides:
: ArBr  +  Li[MgBu]  →  ArMgBu  +  BuBr
;Zinc–halogen exchange
Zinc–halogen exchange:
: LiBuZn + R−I → Li[R−ZnBu] + BuI