Formation of carbon–carbon bonds: organometallic reagents
Organometallic compounds are enormously versatile reagents. The reactivity of organometallics can be correlated with their ionic character. The organic compounds of sodium and potassium are salt-like compounds which are insoluble in non-polar solvents. Organomagnesium compounds, known as Grignard reagents after their discoverer, are prepared and used in solution in an ether, in which they exist as co-ordination complexes and dimers. The standard method for the preparation of a Grignard reagent is the reaction of an organic halide in dry diethyl ether with magnesium metal. Allyl halides react readily in diethyl ether, but since they also react readily with Grignard reagents it is important to keep the concentration of the halide to a minimum in the presence of the Grignard reagent. All the non-metallic elements to which carbon is commonly bonded are more electronegative than carbon. The reagents are not isolated from solution but are used directly for the required synthesis.