Question

The number of geometrical isomers of the complex [Co(NO2)2(NH3)2] is
A . 2
B . 3
C . 4
D . 0

Answer 1

Hint: In this question we have used the concept of geometrical isomerism in coordinate compounds. Geometric isomers are two or more coordination compounds with the same number, kinds, and configurations of atoms as well as bonds (i.e., the connectivity between atoms is the same), but with distinct spatial configurations of the atoms. Geometric isomers are not found in all coordination molecules.

Complete answer:The IUPAC name of [Co(NO2)2(NH3)2] is Diammine trinitro-N-cobalt(II). Co is in a +2 oxidation state.
The number of geometrical isomers of the complex [Co(NO2)2(NH3)2] is 2.

The correct answer is A

Additional Information:
Geometric isomers are metal complexes that only differ in which ligands are located next to one another (cis) or directly across from one another (trans) in the coordination sphere of the metal. They are crucial for octahedral and square planar complexes.
It does not matter which vertex the ligand B occupies in a square planar MA3B complex because all square vertices are equivalent; as a result, only one geometrical isomer is viable in this situation (and in the analogous MAB3 case). Because the four structures displayed here may be stacked by merely rotating the complex in space, they are all chemically equivalent.
Cis and trans isomers can be found in octahedral complexes as well. Similar to square planar complexes, octahedral complexes with only one ligand that differs from the other five are only capable of having one structure (MA5B). The six vertices of an octahedron are equivalent, despite the fact that we typically depict them in a fashion that says the four "in-plane" ligands and the two "axial" ligands are distinct. As a result, any MA5B structure can be superimposed on any other representation by simply rotating the molecule in space, regardless of how we depict it.

Note: The only compounds with geometric isomerism are square planar and octahedral.
Tetrahedral compounds do not exhibit geometric isomerism since each Ligand is positioned in the same way around the center metal atom or ion in space.