Question

The correct IUPAC name of the complex [Pt(NH$_3$)$_2$Cl$_2$] is:

• A. diamminedichloridoplatinum (IV)
• B. diamminedichloridoplatinum (II)
• C. dichloridodiammineplatinum (IV)
• D. dichloridodiammineplatinum (II)

Hint:

In coordination nomenclature: ammine (NH$_3$), aqua (H$_2$O), chlorido (Cl$^-$). Always write ligands alphabetically and include oxidation state of metal.

Answer 1

The Correct Option is B

To determine the correct IUPAC name of the complex [Pt(NH₃)₂Cl₂], let's follow the naming rules for coordination compounds:

1. Identify the ligands and the central metal atom. Here, the ligands are ammonia (NH₃) and chloride (Cl), and the central metal atom is platinum (Pt).
2. Name the ligands:
   • Ammonia is a neutral ligand and is named as "ammine".
   • Chloride is an anionic ligand and is named as "chlorido".
3. List the ligands alphabetically, regardless of charge. Thus, ammine comes before chlorido.
4. Determine the oxidation state of the central metal. Here, the complex is neutral, and since ammonia is neutral and each chloride contributes -1, the oxidation state of platinum can be calculated as follows: 0 = 2 \times 0 + 2 \times (-1) + \text{Oxidation state of Pt}
   Solving gives the oxidation state of platinum as +2.
5. Name the metal. Since the complex is neutral, we simply use the name of the metal, and specify its oxidation state in Roman numerals in parentheses. Therefore, it is "platinum (II)".

Combining these observations, the complete IUPAC name for the complex [Pt(NH₃)₂Cl₂] is "diamminedichloridoplatinum (II)".

The correct option is diamminedichloridoplatinum (II), as given in the answer options.

• The incorrect options either have the incorrect oxidation state or use incorrect naming patterns. For example, "platinum (IV)" implies a higher oxidation state than present, and "dichloridodiammine" incorrectly orders the ligands.