Number of complexes which show optical isomerism among the following is _______.
\( \text{cis-}[\mathrm{Cr(ox)_2Cl_2}]^{3-},\ [\mathrm{Co(en)_3}]^{3+},\ \text{cis-}[\mathrm{Pt(en)_2Cl_2}]^{2+},\ \text{cis-}[\mathrm{Co(en)_2Cl_2}]^{+},\ \text{trans-}[\mathrm{Pt(en)_2Cl_2}]^{2+},\ \text{trans-}[\mathrm{Cr(ox)_2Cl_2}]^{3-} \)