What is the IUPAC name of [Pt(NH₃)₂Cl₂]?

The correct option is Diamminedichloridoplatinum (II).

To determine the correct IUPAC name of the coordination complex $\left[\mathrm{Pt}\right({\mathrm{NH}}_3{)}_2{\mathrm{Cl}}_2]$, we follow the standard IUPAC nomenclature rules for coordination compounds step-by-step:

1. Identify and Name the Ligands:
The complex contains two types of ligands attached to the central platinum ($\mathrm{Pt}$) metal atom:
• ${\mathrm{NH}}_3$ is a neutral ligand named ammine. Since there are two ammine ligands, we use the prefix "di-", giving diammine.
• ${\mathrm{Cl}}^{-}$ is an anionic ligand named chlorido (or chlorido/chloro). Since there are two chloride ligands, we use the prefix "di-", giving dichlorido.

2. Alphabetical Order of Ligands:
Ligands are listed alphabetically in the IUPAC name regardless of their charge. Comparing "ammine" (starts with 'a') and "chlorido" (starts with 'c'), ammine comes first. Therefore, the ligand part of the name is diamminedichlorido.

3. Name the Central Metal Atom:
Since the complex $\left[\mathrm{Pt}\right({\mathrm{NH}}_3{)}_2{\mathrm{Cl}}_2]$ is neutral, the name of the central metal remains unchanged as platinum.

4. Determine the Oxidation State of the Central Metal:
Let the oxidation state of Platinum ($\mathrm{Pt}$) be $x$.
• The ammine ligand (${\mathrm{NH}}_3$) is neutral, so its charge is $0$.
• The chlorido ligand (${\mathrm{Cl}}^{-}$) is anionic, carrying a charge of $-1$ each.
Setting the sum of the charges equal to the overall charge of the complex (which is $0$):

$x+2\left(0\right)+2(-1)=0$

$x-2=0$

$x=+2$

Thus, the oxidation state of platinum is $+2$, which is represented by the Roman numeral (II) in parentheses.

Combining all the parts together, the IUPAC name is written as a single word: Diamminedichloridoplatinum (II).