Question

how many geometrical isomers for [Co(CN)2(NH3)3(H2O)]+

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (C)

3

Answer 2

The complex is of the type $[MA_2B_3C]$ where A=CN⁻, B=NH₃, C=H₂O. We consider the possible arrangements of the ligands in an octahedral geometry.

We can fix the position of the two A ligands (CN⁻), which can be either trans or cis to each other.

1. If the two A ligands are trans, there is only one way to arrange the remaining three B ligands and one C ligand.

2. If the two A ligands are cis, there are two distinct ways to arrange the remaining three B ligands and one C ligand, based on the position of the C ligand relative to the A ligands (cis to both A's, or trans to one A and cis to the other A).

These three arrangements result in three distinct geometrical isomers.

Therefore, the answer is 3.