$(I)\, [CrCl_2(NO_2)_2(NH_3)_2]^-$ $(II)\, [Co(NO_2)_3(NH_3)_3]$
$(III)\, [PtCl(NO_2)(NH_3 )(py)]$ $(IV)\, [PtBrCl(en)]$
$(I)\,\,\,-\,\,\,(II)\,\,\,-\,\,\,(III)\,\,\,-\,\,\,(IV)$
$(I)$ $K[Co(NH_3)_2(NO_2)_4$ $(II)$ $[Cr(NH_3)_3(NO_2)_3]$ $(III)$ $[Cr(NH_3)_5NO_2]_3[CO(NO_2)_6]_2$ $(IV)$ $Mg[Cr(NH_3) (NO_2)_5]$