$(I)\, [CrCl_2(NO_2)_2(NH_3)_2]^-$ $(II)\, [Co(NO_2)_3(NH_3)_3]$
$(III)\, [PtCl(NO_2)(NH_3 )(py)]$ $(IV)\, [PtBrCl(en)]$
$(I)\,\,\,-\,\,\,(II)\,\,\,-\,\,\,(III)\,\,\,-\,\,\,(IV)$
$(i)\, [Cr(NO_3)_3 (NH_3)_3]$ $(ii)\, K_3[Co(C_2O_4)_3]$
$(iii)\, K_3[CoCl_2(C_2O_4)_2]$ $(iv)\, [CoBrCl(en)_2]$