Question

According to IUPAC nomenclature sodium nitroprusside is named as

• A. sodium pentacyanonitrosyl ferrate (II)
• B. sodium pentacyanonitrosyl ferrate (III)
• C. sodium nitroferricyanide
• D. sodium nitroferrocyanide

Answer 1

The Correct Option is B

The compound given is sodium nitroprusside, which has the chemical formula Na₂[Fe(CN)₅NO]. To determine its IUPAC name, we need to understand the structure and composition of the complex.

Let's break down the compound:

1. Central Metal Ion: The metal present is iron (Fe).
2. Oxidation State: To find the oxidation state of iron in the complex, consider the charges:
   • Cyanide ion (CN^-) has a charge of -1, and there are 5 such ligands, contributing to a total charge of -5.
   • The nitrosyl group (NO) is considered as a neutral ligand.
   • The entire complex ion [Fe(CN)₅NO]^-2 has a charge of -2.
   Let the oxidation state of Fe be x. Hence, we can write:
   x + 5(-1) + 0 = -2. Solving, we get x = +3.
3. Ligands: There are two types of ligands:
   • Cyanide: CN
   • Nitrosyl: NO
   As per IUPAC naming conventions, prefix the number of each ligand type (penta for five) and their names (cyano for CN and nitrosyl for NO).
4. IUPAC Name: Combine the information:
   • Complex Name: The complex is named as "pentacyanonitrosyl ferrate".
   • Oxidation State: Since Fe is in the +3 oxidation state, it is denoted in Roman numerals as (III).
   Therefore, the complete IUPAC name of the compound is "sodium pentacyanonitrosyl ferrate (III)".

Thus, the correct answer is sodium pentacyanonitrosyl ferrate (III).

Let's briefly see why the other options are incorrect:

• Sodium pentacyanonitrosyl ferrate (II): Incorrect because the oxidation state of iron is not +2.
• Sodium nitroferricyanide: This is a non-systematic name and does not conform to IUPAC naming for complex compounds.
• Sodium nitroferrocyanide: Again, a non-systematic name and does not use standard IUPAC conventions.

Understanding the correct IUPAC naming conventions is essential for deciphering the structure and nomenclature of complex compounds.