Question

Identify the IUPAC name for the coordination compound \( [Co(NH_3)_6]Cl_3 \).

• A. Hexaamminecobalt(II) chloride
• B. Hexaamminecobalt(III) chloride
• C. Hexamminecobalt(III) chloride
• D. Hexaamminecobalt(II) trichloride

Hint:

In coordination compounds: - \(NH_3\) ligand is named ammine. - Neutral ligands do not affect oxidation state calculations. - The oxidation state of the metal balances the charge of the complex ion.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Naming a coordination compound requires identifying the ligands, the central metal atom, its oxidation state, and the counter ions.
Step 2: Key Formula or Approach:
Rule 1: Name the cation before the anion.
Rule 2: Inside the complex, name ligands alphabetically (though here only one type exists).
Rule 3: Use prefixes like 'hexa' for six.
Rule 4: State metal oxidation number in Roman numerals.
Step 3: Detailed Explanation:
1. Ligands: There are 6 \( NH_3 \) groups. The IUPAC name for \( NH_3 \) as a ligand is "ammine". Six groups make it "hexaammine".
2. Central Metal: The metal is Cobalt (\( Co \)). Since the complex is a cation, the name remains Cobalt.
3. Oxidation State: Let the oxidation state of \( Co \) be \( x \).
\( NH_3 \) is a neutral ligand (charge = 0).
\( Cl \) has a charge of \( -1 \).
Sum of charges: \( x + 6(0) + 3(-1) = 0 \)
\( x - 3 = 0 \Rightarrow x = +3 \).
The Roman numeral is (III).
4. Counter Ion: The ion outside the bracket is chloride.
Step 4: Final Answer:
Combining these, the name is Hexaamminecobalt(III) chloride.