Question

Incorrect option about the complex $\left[Fe\right(CO{)}_5]$ is:

• A. Its effective atomic number is 36
• B. It has a square pyramidal structure
• C. It has an hybridization of $ds{p}^3$
• D. It has a larger $CO$ bond length than the normal $CO$ bond length

Answer 1

The correct option is B It has a square pyramidal structure

In $Fe(CO{)}_5$, Fe is neutral having 26 electrons and total of 10 electrons are donated by $5CO$ ligands. So EAN = 36.

It has a trigonal bipyramidal geometry.

$CO$ is a very strong field ligand which promotes the pairing of electrons in $Fe$. Hence an inner-orbital complex is formed with $ds{p}^3$ hybridization.

Due to the formation of synergic bond, $CO$ bond length increases than the normal $CO$ bond length.