Indicate the type of isomerism exhibited by the following complexes and draw the structures for these isomers:
(i) `K[Cr(H_(2)O)_(2)(C_(2)O_(4))_(2)`
(ii) `[Co(en)_(3)]Cl_(3)`
(iii) `[Co(NH_(3))_(5)(NO_(2))](NO_(3))_(2)`
(iv) `[Pt(NH_(3))(H_(2)O)Cl_(2)]`

Explanation

(i) Both geometrical (cis-, trans-) and optical isomers for cis can exist.
(ii) Two optical isomers can exist.
(iii) There are 10 possible isomers. (Hint: There are geometrical, ionisation
and linkage isomers possible).
(iv) Geometrical (cis-, trans-) isomers can exist.