The cluster types of $\mathrm{[Fe_5(CO)_{14}N]^{-}}$ and $\mathrm{[Co_6(CO)_{13}N]^{-}}$ are, respectively,
(a)nido-, nido
(b)nido-, closo
(c)closo-, nido
(d)closo-, closo
Answer
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Explanation
$[\mathrm{Fe_5(CO)_{14}N}]^{-}$: $\mathrm{TEC}=(8\times 5)+(14\times 2)+5+1=40+28+6=74$$\mathrm{PEC}=74-(12\times 5)=14$; $\mathrm{PEC}/2=14/2=7$, i.e. $n+2$. Thus, it is a nido cluster.$[\mathrm{Co_6(CO)_{13}N}]^{-}$: $\mathrm{TEC}=(9\times 6)+(13\times 2)+5+1=54+26+6=86$$\mathrm{PEC}=86-(6\times 12)=14$; $\mathrm{PEC}/2=14/2=7$, i.e. $n+1$. Thus, it is a closo cluster.