Question

Write IUPAC name of the following compound : \( [Cr(NH_{3})_{4} (ONO)Cl] NO_{3} \)

Hint:

Always double-check the donor atom for \( NO_{2} \). If it's written \( ONO \), the oxygen is the donor, so the name is nitrito-O. If it's \( NO_{2} \), the nitrogen is the donor, so it's nitrito-N.

Answer 1

Concept:

• IUPAC rules for coordination compounds require naming ligands in alphabetical order, followed by the metal.

• The oxidation state of the central metal must be indicated in Roman numerals in parentheses.

• If the complex is a cation, the metal's standard name is used.

• Ambidentate ligands like \( ONO^{-} \) must specify the donor atom.
Step 1: Determine the oxidation state of Chromium
Let the oxidation state of \( Cr \) be \( x \).
The charges on the components are: - Ammine (\( NH_{3} \)) = \( 0 \) - Nitrito (\( ONO^{-} \)) = \( -1 \) - Chloro (\( Cl^{-} \)) = \( -1 \) - Nitrate (\( NO_{3}^{-} \)) (counter ion) = \( -1 \)
Summing for the neutral molecule: \( x + 4(0) + (-1) + (-1) + (-1) = 0 \) \( x - 3 = 0 \Rightarrow x = +3 \).

Step 2: Alphabetize the ligands
- \( NH_{3} \): ammine - \( Cl \): chloro - \( ONO \): nitrito-O
Alphabetical order: ammine \( \gt \) chloro \( \gt \) nitrito-O.

Step 3: Construct the full name
Combine the ligands (with prefixes), the metal, its oxidation state, and the counter ion: Tetraamminechloronitrito-O-chromium(III) nitrate. The final answer is Tetraamminechloronitrito-O-chromium(III) nitrate.