$[\overset{-1}{\mathop{Mn}}\,{{(CO)}_{4}}(N{{O}^{+}})]:$ No unpaired $e^-$ either on ligands or on $\overset{-1}{\mathop{Mn}}$ hence it is diamagnetic
$(i)$ $[Ni(CO)_4], \,sp^3$
$(ii)$ $[Ni(CN)_4]^{2-}, \,sp^3$
$(iii)$ $[CoF_6]^{3-}, \,d^2sp^3$
$(iv)$ $[Fe(CN)_6]^{3-}, \,sp^3d^2$
(મુક્ત $CO$ માં $C-O$ બંધલંબાઇ $1.128\,\mathop A\limits^o $ છે.