Structure of Organometallic Compounds
In the synthesis of Grignard compounds (organomagnesium halides, RMgX), the solvent, which is usually diehtyl ether or tetrahydrofuran (THF), plays a most crucial role. The magnesium atom of a Grignard compound lacks four electrons to achieve an electron octet.
In organometallic compounds such as organolithium and Grignard compounds, the carbon is considerably negatively polarized. Thus, due to the large electronegativity difference between the carbon and the metal, the carbon is nucleophilic. The carbon-metal bond is strongly polarized. As a result, the chemical properties of such an organometallic compound resemble that of separated magnesium cations and alkyl anions even though the magnesium atom and the alkyl group are not actually separated into ions.
In the mechanism of Grignard compound formation, a radical intermediate evolves. Grignard compounds hydrolyze rapidly when they are treated with water. The hydrolysis yields the corresponding alkane and magnesium hydroxide. Therefore, the synthesis of Grignard compounds and the subsequent nucleophilic attack of the Grignard compound on an electrophile, such as a carbonyl compound, must be performed out of contact with water.