1. The metal-carbon double bond

The simple metal-carbon bond can be easily created. First demonstrated by Frankland's discovery of organozinc compounds, then by Grignard's discovery of organomagnesium compounds, it became a general feature of the synthesis of organometallic compounds in which the metal is a transition element.

Interpreted as a covalent double bond, it suggests the existence of metal-carbon double bonds, in which the carbon group appears as a carbene. The problem is the chemical route to these compounds. The discovery was made by E.O. Fischer.