${\left[ Ni ( CN )_4\right]^{2-},\left[ Ni ( CO )_4\right],\left[ NiCl _4\right]^{2-}}$
${\left[ Fe ( CN )_6\right]^{4-},\left[ Cu \left( NH _3\right)_4\right]^{2+}}$
${\left[ Fe ( CN )_6\right]^{3-} \text { and }\left[ Fe \left( H_2O\right)_6\right]^{2+}}$
$(I)$ $K[Co(NH_3)_2(NO_2)_4$ $(II)$ $[Cr(NH_3)_3(NO_2)_3]$ $(III)$ $[Cr(NH_3)_5NO_2]_3[CO(NO_2)_6]_2$ $(IV)$ $Mg[Cr(NH_3) (NO_2)_5]$