In a particular isomer of $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_4 \mathrm{Cl}_2\right]^0$, the $\mathrm{Cl}-\mathrm{Co}-\mathrm{Cl}$ angle is $90^{\circ}$, the isomer is known as:

• A

  optical isomer
• Correct answer
  B

  cis-isomer
• C

  position isomer
• D

  linkage isomer

Solution

The structure is shown below:

Hence, the correct answer is option: 'B'.