IUPAC Name of Nickel Complex Compound

To determine the correct IUPAC name for the coordination compound $[\text{Ni}(\text{NH}_3)_4][\text{NiCl}_4]$, we follow the standard IUPAC nomenclature rules for coordination complexes:

1. Identification of Cation and Anion Spheres:
   In ionic coordination compounds, the cationic complex is written and named first, followed by the anionic complex:
   $\text{Cationic sphere: } [\text{Ni}(\text{NH}_3)_4]^{x+}$
   $\text{Anionic sphere: } [\text{NiCl}_4]^{y-}$

2. Determination of Oxidation States:

   • $\text{NH}_3$ is a neutral ligand (charge $= 0$).
   • $\text{Cl}^-$ is a mono-anionic ligand (charge $= -1$).

   Assuming the most stable oxidation state of Nickel ($\text{Ni}$) in simple amine/halo complexes is $+2$:

   • For the cationic species $[\text{Ni}(\text{NH}_3)_4]^{2+}$:
     $\text{Oxidation State of Ni} + 4(0) = +2 \implies \text{Oxidation State of Ni} = +2\text{ (II)}$
   • For the anionic species $[\text{NiCl}_4]^{2-}$:
     $\text{Oxidation State of Ni} + 4(-1) = -2 \implies \text{Oxidation State of Ni} = +2\text{ (II)}$

   Since the total charges balance out ($+2$ and $-2$), the formula correctly represents the coordination compound.

3. Naming the Cationic Complex $[\text{Ni}(\text{NH}_3)_4]^{2+}$:

   • The four ammine ligands are named first: tetraammine.
   • Since the complex is a cation, the central metal retains its standard name: nickel.
   • The oxidation state is appended in Roman numerals: (II).
   • Cation Name: Tetraamminenickel (II)

4. Naming the Anionic Complex $[\text{NiCl}_4]^{2-}$:

   • The four chloro ligands are named first: tetrachloro (or tetrachlorido).
   • Since the complex is an anion, the suffix "-ate" is added to the central metal name: nickelate.
   • The oxidation state is appended in Roman numerals: (II).
   • Anion Name: tetrachloronickelate (II)

5. Combining Cation and Anion Names:
   Combining both parts in order (cation followed by anion) yields:
   $\text{Tetraamminenickel (II) - tetrachloronickelate (II)}$

This matches Option (C).

Correct Answer: C