Question

In $Fe(CO{)}_5,$ the $Fe-C$ bond possesses :

• A. Ionic character
• B. $\sigma -$ character only
• C. $\pi -$character
• D. Both $\sigma -$ and $\pi -$ characters

Answer 1

The correct option is D Both $\sigma -$ and $\pi -$ characters

The metal-carbon bond in metal carbonyls possess both $\sigma$ and $\pi$ character. The $M–C\sigma$ bond is formed by the donation of lone pair of electrons on the carbonyl carbon into a vacant orbital of the metal. The $M–C\pi$ bond is formed by the donation of a pair of electrons from a filled $d-$orbital of metal into the vacant antibonding ${\pi }^{\ast }$ orbital of carbon monoxide. The metal to ligand bonding creates a synergic effect which strengthens the bond between CO and the metal.