Question

Show the geometrical isomers of \([Fe(NH_3)_2(CN)_4]\).

Hint:

In octahedral complexes with two different types of ligands, geometrical isomerism can occur, resulting in cis and trans isomers depending on the relative positions of the ligands.

Answer 1

In this question, we are dealing with the complex \([Fe(NH_3)_2(CN)_4]\), which is an octahedral coordination complex. The central metal ion is iron (Fe), surrounded by two ammonia (NH\(_3\)) molecules and four cyanide (CN\(^-\)) ions. The coordination number of the metal ion is 6, forming an octahedral geometry. Geometrical Isomerism in Octahedral Complexes:
Geometrical isomerism arises in octahedral complexes when there are different possible spatial arrangements of ligands. In this case, the complex \([Fe(NH_3)_2(CN)_4]\) can have cis and trans isomers based on the arrangement of the ligands. 1. Cis-Isomer: In the cis configuration, the two NH\(_3\) molecules are placed next to each other, i.e., they occupy adjacent positions (90° apart) in the octahedral arrangement. The four cyanide ions are placed at the remaining positions, opposite each other. This creates a symmetrical arrangement of the ligands in the octahedral complex. The formula for this isomer can be represented as: \[ [Fe(NH_3)_2(CN)_4]_{\text{cis}} \] 2. Trans-Isomer: In the trans configuration, the two NH\(_3\) molecules are placed opposite each other, i.e., they occupy opposite positions (180° apart) in the octahedral arrangement. The four cyanide ions occupy the remaining positions. This arrangement is different from the cis-isomer and results in a distinct geometric shape. The formula for this isomer is: \[ [Fe(NH_3)_2(CN)_4]_{\text{trans}} \] Conclusion: - The cis-isomer has the two NH\(_3\) molecules adjacent to each other, while in the trans-isomer, the NH\(_3\) molecules are opposite each other. These two different spatial arrangements of the ligands lead to geometrical isomerism in the complex.