Identify the complexes and their geometries

• Triamminetrinitrocobalt(III) means: $[\text{Co}(NH_3)_3(NO_2)_3]$ Here, cobalt(III) is a coordination number 6 complex, so it is octahedral.

• Trioxalatochromate(III) means: $[\text{Cr}(C_2O_4)_3]^{3-}$ Oxalate $C_2O_4^{2-}$ is a bidentate ligand. Three oxalate ligands occupy 6 coordination positions, so this is also octahedral.

Find geometrical isomers of $[\text{Co}(NH_3)_3(NO_2)_3]$

This is an octahedral complex of the type: $[MA_3B_3]$ where

• $A = NH_3$
• $B = NO_2$

For an octahedral complex of type $[MA_3B_3]$, there are two geometrical isomers:

1. fac (facial): all three identical ligands occupy one face of the octahedron.
2. mer (meridional): the three identical ligands lie along a meridian.

Hence, $X = 2$

Find geometrical isomers of $[\text{Cr}(C_2O_4)_3]^{3-}$

This is an octahedral complex with three identical bidentate ligands, i.e. type: $[M(AA)_3]$

Such a complex does not show geometrical isomerism because all three ligands are identical and arranged equivalently in octahedral geometry.

It can show optical isomerism ($\Delta$ and $\Lambda$ forms), but the question asks only for geometrical isomers.

Therefore, $Y = 0$

Compute $X+Y$

$X + Y = 2 + 0 = 2$

Comparison with stored answer

• Derived answer: $2$
• Stored correct answer: $2$

They match.