$[Co(NH_3)_4(NO_2)_2]^+$ ; $\mu_{eff} = 0$
$[Ag(CN)_2)$ ; $\mu_{eff} = 0$
$[CuBr_4]^{2-}$ ; $\mu_{eff} = 1.732 \,BM$
(પ.ક્ર.: $Mn\, = 25, Co\, = 27, Ni\, = 28, Zn\, = 30$)