Question

The IUPAC name of the following complex [Cr(H\(_2\)O)\(_3\)(NH\(_3\))\(_3\)]Cl\(_3\) is

• A. Triaminetriquachromium(III) chloride
• B. Triaquatriaminemechromium(III) chloride
• C. Triaquatriaminemechromium(II) chloride
• D. Triaminetriquachromium(II) chloride
• E. Triaquatriaminemechromium(III) trichloride

Hint:

Remember to use proper prefixes (di, tri, tetra) and list ligands alphabetically by their root name (e.g., 'ammine' before 'aqua').

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
This question requires applying the rules of IUPAC nomenclature for naming coordination compounds.
Step 2: Detailed Explanation
Let's break down the naming process for the complex \([\text{Cr}(\text{H}_2\text{O})_3(\text{NH}_3)_3]\text{Cl}_3\).
1. Identify Ligands: The ligands inside the coordination sphere are H₂O and NH₃. - H₂O as a ligand is named "aqua". - NH₃ as a ligand is named "ammine" (note the double 'm'). 2. Name Ligands Alphabetically: We list the ligands in alphabetical order, irrespective of their prefixes. "Ammine" comes before "aqua". 3. Use Prefixes for Number of Ligands: There are three ammine ligands, so we use the prefix "tri-", giving "triammine". There are three aqua ligands, so we use "triaqua". Combining these gives: "triamminetriaqua". 4. Identify the Central Metal Atom: The central metal is Cr, which is Chromium. Since the complex ion is cationic (positively charged), the metal name is used as is: "chromium". 5. Determine the Oxidation State of the Metal: Let the oxidation state of Cr be \(x\). The ligands H₂O and NH₃ are neutral (charge = 0). The counter ion is chloride (Cl⁻), and there are three of them, so the total charge of the counter ions is -3. For the compound to be neutral, the charge of the coordination sphere \([\text{Cr}(\text{H}_2\text{O})_3(\text{NH}_3)_3]\) must be +3. Therefore: \(x + 3(0) + 3(0) = +3 \implies x = +3\). The oxidation state is written in Roman numerals in parentheses: (III). 6. Name the Counter Ion: The counter ion is Cl⁻, which is named "chloride". We do not use prefixes like "tri-" for counter ions. 7. Assemble the Full Name: Putting it all together: (Ligands alphabetically) + (Metal name) + (Oxidation state) + (Counter ion name) Triamminetriaquachromium(III) chloride
Step 3: Final Answer
The correct IUPAC name is Triamminetriaquachromium(III) chloride.