The correct answer is option 3. [Ni(CO)4].
Among the given options, the metal complex where the central metal atom has zero valency is $(3)$ $[Ni(CO)_4]$.
Explanation:
In option $(1)$, $[Cu(NH_3)_4]SO_4$, copper ($Cu$) is surrounded by $4$ ammonia ($NH_3$) ligands. Therefore, the valency of copper in this complex is $4$.
In option $(2)$, $K_3[Fe(CN)_6]$, iron ($Fe$) is coordinated to $6$ cyanide ($CN^-$) ligands. Hence, the valency of iron in this complex is $6$.
In option $(4)$, $[Pt(NH_3)_2Cl_2]$, platinum ($Pt$) is coordinated to $2$ ammonia ($NH_3$) ligands and $2$ chloride ($Cl^-$) ligands. The coordination number of platinum in this complex is $4$, indicating a valency of $4$.
However, in option $(3)$, $[Ni(CO)_4]$, nickel ($Ni$) is coordinated to $4$ carbon monoxide ($CO$) ligands. The coordination number of nickel in this complex is $4$, but since carbon monoxide is a neutral ligand that donates its own electrons, the valency of nickel in this complex is considered to be zero. This is because the nickel atom does not contribute any of its own valence electrons for bonding in this complex.
Therefore, the correct answer is $(3)$, $[Ni(CO)_4]$, as the central metal atom (nickel) has zero violence in this complex. |
