Question

Which of the following is the correct IUPAC name for the \([\text{Pt}(\text{NH}_3)_2\text{Cl(\text{NO}_2)]\) coordination compound?}

• A. Diamminechloridonitrito-N-platinum(II)
• B. Diamminechloridonitrido-N-platinum(III)
• C. Diamminechloridonitrito-N-platinate(II)
• D. Diamminechloridenitrido-N-platinum(II)

Hint:

Common IUPAC traps:
- \(\text{NH}_3\) is spelled 'ammine' (with double 'm').
- Use 'platinate' only when the complex carries a net negative charge. For neutral or cationic complexes, use 'platinum'.

Answer 1

The Correct Option is A

Concept:
Coordination complexes are systematically named according to IUPAC nomenclature:
1. Ligands are listed alphabetically before the central metal.
2. Neutral ligands retain their name (with exceptions like \(\text{NH}_3 = \text{ammine}\)), while anionic ligands end in '-o' or '-ido'.
3. Ambidentate ligands include the coordinating donor atom.
4. The oxidation state of the metal is indicated in Roman numerals in parentheses.
5. For neutral or cationic coordination spheres, the metal keeps its common name. The suffix '-ate' is used only for anionic complexes.

Step 1: Determining the Oxidation State of the Metal:
Let the oxidation state of the platinum atom be \(x\).
The charges of the coordinated ligands are:
- Ammine (\(\text{NH}_3\)): neutral ligand, charge = \(0\)
- Chlorido (\(\text{Cl}^-\)): monoanionic ligand, charge = \(-1\)
- Nitrito-N (\(\text{NO}_2^-\)): monoanionic ligand, charge = \(-1\)
The overall complex molecule is neutral, so:
\[ x + 2(0) + (-1) + (-1) = 0 \implies x - 2 = 0 \implies x = +2 \] Thus, platinum is in the \(+2\) oxidation state, written as (II).

Step 2: Alphabetical Ordering of Ligands:
- Two \(\text{NH}_3\) ligands: 'diammine' (alphabetized under 'a')
- One \(\text{Cl}^-\) ligand: 'chlorido' (alphabetized under 'c')
- One \(\text{NO}_2^-\) coordinated through nitrogen: 'nitrito-N' (alphabetized under 'n')
Thus, the correct alphabetical sequence is: diamminechloridonitrito-N.

Step 3: Constructing the Full Name:
Because the coordination sphere is neutral, the metal is named as 'platinum', followed by its oxidation state (II).
Combining the components gives:
\[ \text{Diamminechloridonitrito-N-platinum(II)} \] Final Answer:
The correct IUPAC name is Diamminechloridonitrito-N-platinum(II), corresponding to option (A).