In a particular isomer of $[Co(NH_3)_4Cl_2]^0$,the $Cl-Co-Cl$ angle is $90^\circ$. This isomer is known as:

The complex which has facial $(fac)$ and meridional $(mer)$ isomers is
(Given: $py = \text{pyridine}$ and $en = H_2N-CH_2-CH_2-NH_2$)

Indicate the types of isomerism exhibited by the following complexes and draw the structures for these isomers:
$(i)$ $K[Cr(H_2O)_2(C_2O_4)_2]$
$(ii)$ $[Co(en)_3]Cl_3$
$(iii)$ $[Co(NH_3)_5(NO_2)](NO_3)_2$
$(iv)$ $[Pt(NH_3)(H_2O)Cl_2]$

What is the number of possible geometric isomers for the complex $[Pt(Py)(NH_3)BrCl]$?

Select the incorrect match.

Indicate the complex or complex ion which does not show any geometrical isomerism: