Chemistry - Coordination Chemistry Question with Solution | TestHub

Explain Question:

Finding the species that loses an electron to reach a stable state.

Concept:

Effective Atomic Number (EAN) Rule.

Solution:

Metal carbonyls are most stable when their EAN equals 36 (Krypton's configuration). A species acts as a reducing agent if it loses an electron to reach this stable count of 36.

Calculation:

Formula:

EAN = Z - (Oxidation state ) + 2 × (Number of ligand )

${\left[\mathrm{Co}(\mathrm{CO}{)}_4\right]}^{-}:27-\left(-1\right)+2\left(4\right)=36\left(stable\right)$

$\mathrm{Mn}(\mathrm{CO}{)}_6:25-0+2\left(6\right)=37$ (Unstable; loses 1e^- to become 36)

$\mathrm{Mn}(\mathrm{CO}{)}_5:25-0+2\left(5\right)=35$ (Acts as oxidizing agent to reach 36)

$\mathrm{Cr}(\mathrm{CO}{)}_6:24-0+2\left(6\right)=36$ (Stable)

(Stable) (Unstable; loses 1e to become 36) (Acts as oxidizing agent to reach 36) (Stable) Final Answer: Option (2)