${\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+},\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+},\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+},}$
${\left[\mathrm{Cu}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+},\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}}$
$(I)\, [(Ph_3P)_2PdCl_2PdCl_2]$ $(II)\,[NiBrCl(en)]$
$(III)\, Na_4 [Fe(CN)_5 NOS]$ $(IV)\, Cr(CO)_3(NO)_2$
$(I)\,-\,(II)\,-\,,(III)\,-\,(IV)$
$[Co(en)_3]\,[Cr(C_2O_4)_3]$
$[Cu(NH_3)_4]\, [CuCl_4]$
$[Ni(en)_3]\,[Co(NO_2)_6]$
(Atomic nos. $Mn = 25,\,Fe = 26,\,Co = 27$)
($R $ = alkyl group; $en$ = ethylenediamine)