$(I)\, [Ni(CN)_4]^{2-}\,\,\,(II)\, [NiCl_4]^{2-}\,\,\,(III)\,Ni(CO_4)\,\,\,$
$(IV)\, [Ni(H_2O)_6 ]^{2+}$
$1.$ $[Co(NH_3)_5NO_2]Cl_2$ અને $[Co(NH_3)_5ONO]Cl_2$ $-$ બંધનીય
$2.$ $[Cu(NH_3)_4] [PtCl_4]$ અને $[Pt(NH_3)_4] [CuCl_4]$ $-$ સવર્ગ
$3.$ $[Pt(NH_3)_4Cl_2]Br_2$ અને $[Pt(NH_3)_4Br_2]Cl_2$ $-$ આયનીકારક