Organometallic compounds are compounds that contains a carbon metal bond. You are already familiar with some organometallic compound like sodium acetylide (NaC==CH) and alkyl lithium which has an ionic bond between carbon and sodium or carbon and lithium. But simply having a metal and carbon in the same compound is not sufficient for classification as organometallic. Sodium methoxide (NaOCH3), for example, is not an organometallic compound ; sodium is not bonded directly with carbon atom.
Preparation of organomagnesium : Grignard Reagents
The most important organometallic reagents in organic chemistry are organomagnesium compounds. They are called Grignard reagents. Grignard developed efficient methods for the preparation of organic derivatives of magnesium and their application in the synthesis of many organic compounds.
Grignard reagents are prepared directly from organic halides by reaction with magnesium, a group II metal in the presence of ether as solvent.
Grignard reagent shows following reactions.
(i) Substitution reactions
When grignard reagent reacts with compounds containing active ‘H’ or RX. It shows substitution reaction.
(ii) Addition reaction
Grignard reagent reacts with compounds containing multiple bonds between atoms with electronegativity difference. It shows addition reaction between two atoms.
(i) > C = O (ii) > C = S (iii) – C º N (iv) > S = O, etc.