Explanation:

The given complex is [CoCl2(en)(NH3)2]. The coordination number is 6 as there are six ligands bound to the central metal atom (Co). The ligands are two Cl-, two NH3 and one en (ethylenediamine). The complex is octahedral in shape.

Different types of isomers:

1. Ionization isomers: These isomers arise due to the interchange of a ligand with an anion outside the coordination sphere. For example, [Co(NH3)5Cl]SO4 and [Co(NH3)5SO4]Cl are ionization isomers.

2. Hydrate isomers: These isomers arise due to the presence of water molecules inside or outside the coordination sphere. For example, [Cr(H2O)6]Cl3 and [Cr(H2O)5Cl]Cl2.H2O are hydrate isomers.

3. Linkage isomers: These isomers arise due to the presence of a ligand that can bind to the central metal atom through two different atoms. For example, [Co(NH3)5(NO2)]Cl2 and [Co(NH3)5(ONO)]Cl2 are linkage isomers.

4. Geometrical isomers: These isomers arise due to the different spatial arrangement of the ligands around the central metal atom. For example, [CoCl2(en)(NH3)2] can have four geometrical isomers.

Geometrical isomers of the given complex:

The given complex [CoCl2(en)(NH3)2] can have four geometrical isomers due to the different spatial arrangement of the ligands around the central metal atom. These isomers are:

1. cis-[CoCl2(NH3)2(en)] (Cl atoms and NH3 ligands are adjacent to each other)
2. trans-[CoCl2(NH3)2(en)] (Cl atoms and NH3 ligands are opposite to each other)
3. cis-[CoCl(NH3)2(en)Cl] (Cl atoms and en ligand are adjacent to each other)
4. trans-[CoCl(NH3)2(en)Cl] (Cl atoms and en ligand are opposite to each other)

Hence, the number of isomers possible for the octahedral complex [CoCl2(en)(NH3)2] is 4.