Which of the following complex species is not expected to exhibit optical isomerism ?

Question

$\begin{array}{1 1} (1) [Co(en)_3]^{3+} \\ (2) [Co(en)_2Cl_2]^+ \\ (3) [Co(NH_3)_3 Cl_3] \\ (4) [Co(en)(NH_3)_2Cl_2]^+ \end {array}$