Question

Which of the following organometallic compound is $\sigma$ and $\pi$ bonded -

• A. $\left[Fe\right({\eta }^5-C_5{H}_5{)}_2]$
• B. $K\left[PtC{l}_3\right({\eta }^2-C_2{H}_{4}0]$
• C. $\left[Co\right(CO{)}_{5}N{H}_3{]}^{+2}$
• D. $Fe(C{H}_3{)}_3$

Answer 1

The correct option is C $\left[Co\right(CO{)}_{5}N{H}_3{]}^{+2}$

Option (C) is correct.

$\left[Co\right(CO{)}_{5}N{H}_3{]}^{+2}$ is $\sigma$ and $\pi$ bonded.

In this organometallic compound,bond between cobalt and $CO$ ligands have both $\sigma$ and $\pi$ character.$\sigma$- bond formation between metal and carbon of $CO$ takes place by overlap of filled bonding ${\pi }_{2p}$ of $CO$ with an empty metal $d$- orbital.

The 2nd overlap takes place between metal $d$- orbital with an empty antibonding pi orbital of the $CO$ resulting in additional $\pi$- bond between the metal and same $CO$ molecule.