Question

The correct molecular geometry of $Fe{\left(CO\right)}_5$ is:
(Z=26 for Fe)

• A. Octahedral
• B. Tetrahedral
• C. Square pyramidal
• D. Trigonal bipyramidal

Answer 1

The correct option is D Trigonal bipyramidal

Electronic configuration of $Fe$ is $\left[Ar\right]3d^{6}4s^2$.
Since, $CO$ is a strong field ligand, it will pair the unpaired electrons. Due to high CFSE value, two electrons of 4s orbital will move to 3d orbitals. The five $CO$ molecules will then take place in 3d, 4s and 4p gaining $ds{p}^3$ hybridisation.