text: Rieke metals are usually prepared by a reduction of an anhydrous metal chloride with an alkali metal, in a suitable solvent.  For example, Rieke magnesium can be prepared from magnesium chloride with potassium as the reductant:
  :MgCl + 2 K → Mg + 2 KCl
  Rieke originally described three general procedures:
  * Reaction with molten sodium or potassium in a solvent whose boiling point is higher than the metal's melting point, and which can dissolve some of the anhydrous salt, in an inert atmosphere. Suggested combinations were potassium in tetrahydrofuran (THF), sodium in 1,2-dimethoxyethane, and either metal with benzene or toluene. The exothermic reaction takes a few hours, and usually requires refluxing.
  * Reaction with an alkali metal at temperatures below its melting point, with a catalytic amount (5-10% by mole) of an electron carrier such as naphthalene or biphenyl.  This method can be used with lithium as the reducing agent, even at room temperature, and is therefore less hazardous than the previous method; and often results in more reactive powders.
  * Reaction with previously prepared lithium naphthalide or lithium biphenylide instead of lithium.  This process can be carried out at even lower temperatures, below ambient.  Although slower, it was found to produce even smaller particles.
  The alkali metal chloride coprecipitates with the finely divided metal, which can be used in situ or separated by washing away the alkali chloride with a suitable solvent.