5.3:
Properties of Organometallic Compounds
The juvenile hormone — a development regulator in mosquitoes — has 7 out of its 16 C–C bonds formed using organometallic compounds.
Organometallic compounds contain a polar, covalent C–M bond.
Carbon can be part of an alkyl, aryl, allyl, or a benzyl group. For metals, lithium, magnesium, aluminum, tin, copper, and zinc are commonly used.
The greater electronegativity of carbon than the attached metal polarizes the C–M bond towards carbon, making the carbon atom electron-rich in organometallic compounds.
As a visual comparison, examine the C–X bond in alkyl halides. The higher electronegativity of the halogen polarizes the bond towards it, making the carbon atom electron-deficient in haloalkanes.
Organometallic compounds are carbanionic and are useful as strong bases and strong nucleophiles.
As the electronegativity difference between the carbon atom and the metal in the C–M bond increases, the bond's percent ionic character increases. This means, the carbon becomes more nucleophilic and the compounds become more reactive.
5.3:
Properties of Organometallic Compounds
Organometallic compounds are compounds that contain a carbon–metal bond. Carbon belongs to an organyl group like alkyl, aryl, allyl, or benzyl groups. The metal can be from Group I or Group II of the periodic table, a transition metal, or a semimetal.
The carbon–metal bond is polar in nature. The carbon atom is more electronegative than the metal. As a result, the electrons in the carbon–metal bond are pulled towards the carbon atom, making the carbon electron-rich, like a carbanion. The carbanionic character makes an organometallic compound a strong base and a strong nucleophile.
The reactivity of an organometallic compound results from the difference in polarity between the carbon and the metal. As the electronegativity difference increases, the percent ionic character of carbon–metal bond increases. That is to say, as the carbon atom becomes more nucleophilic, the compound becomes more reactive. For example, the carbon–metal bond in organolithium and organomagnesium compounds is more polar than in the organocuprates. Therefore, both organolithium and organomagnesium compounds are more reactive than organocuprates.
Organometallic compounds are named by identifying the metal and using it as the base name. Next, the organyl substituent is identified and used as a prefix to the base name. Further, multiplier prefixes denote the number of such organyl groups present.
If the metal bears any non-carbon substituent, it is identified as an anion and named after the metal.
