[પ.ક્ર.: $Cr= 24,\,Mn= 25, \,Fe= 26, \,Co= 27$]
$(I)\ [Pt(NH_3)_6]Cl_4$
$(II) [Cr(NH_3)_6]Cl_3$
$(III) [Co(NH_3)Cl_2]Cl$
$(IV) K_2[PtCl_6]$