Question

How many isomers are possible in $\left[Cr{\left(en\right)}_{2}B{r}_2\right]$?

Answer 1

$\left[Cr{\left(en\right)}_{2}B{r}_2\right]$ cannot show structural isomerism. Considering stereoisomerism, $\left[Cr{\left(en\right)}_{2}B{r}_2\right]$ can show geometrical isomerism. Thus, we have two forms here - cis and trans.
The trans form is optically inactive due to the presence of a plane of symmetry. However, the cis form is optically active. This means that there are a total of 3 isomers.