$(A)\,\,\,\,[Ni(H_2O)_5NH_3]^{2+},$ $(B)\,\,\,\,[Ni(H_2O)_4(NH_3)_2]^{2+}$ $(C)\,\,\,\,[Ni(H_2O)_3(NH_3)_3]^{2+}$
$(I)\ [Pt(NH_3)_6]Cl_4$
$(II) [Cr(NH_3)_6]Cl_3$
$(III) [Co(NH_3)Cl_2]Cl$
$(IV) K_2[PtCl_6]$