Question

What is IUPAC name of \([ \text{CoCl}_2 (\text{en})_2 ]^+ \)?

• A. Bis (ethylenediamine) dichloro cobalt (III) ion
• B. Dichloro ethylenediamine cobalt (I)
• C. Ethylene diamine cobalt (I) dichloride
• D. Ethylene diamine cobalt chloride

Hint:

In naming coordination compounds, the ligands are named first followed by the metal with its oxidation state in parentheses. "Bis" is used for two identical ligands.

Answer 1

The Correct Option is A

Step 1: Understanding the IUPAC naming convention.
In IUPAC nomenclature, we name coordination complexes by indicating the ligands first, followed by the metal and its oxidation state in parentheses. In this case, the complex contains two ethylenediamine (en) ligands and two chloride ions as ligands, with cobalt in the +3 oxidation state. The prefix "bis" is used for two identical ligands.
Step 2: Analyzing the options.
(A) Bis (ethylenediamine) dichloro cobalt (III) ion: Correct — This follows the IUPAC rules for naming coordination complexes.
(B) Dichloro ethylenediamine cobalt (I): Incorrect — The oxidation state of cobalt should be +3, not +1.
(C) Ethylene diamine cobalt (I) dichloride: Incorrect — The ligand order is incorrect, and the oxidation state is wrong.
(D) Ethylene diamine cobalt chloride: Incorrect — This is a simplified name and does not follow the IUPAC convention for coordination compounds.
Step 3: Conclusion.
The correct answer is (A) Bis (ethylenediamine) dichloro cobalt (III) ion.