text: ;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