Question

IUPAC name of \([\mathrm{Co(NH_3)_4(H_2O)Cl]Cl_2\) is:}

• A. Tetraammineaquachloridocobalt(II) chloride
• B. Tetraammineaquachloridocobalt(III) chloride
• C. Tetraammineaquachloridocobalt(I) chloride
• D. Tetraammineaquachloridocobalt(0) chloride

Hint:

Neutral ligands such as \(NH_3\) and \(H_2O\) contribute zero charge when calculating oxidation state of the central metal ion.

Answer 1

The Correct Option is B

Step 1: Determine charge on the complex ion.
There are two chloride ions outside the coordination sphere. Hence, \[ [\mathrm{Co(NH_3)_4(H_2O)Cl}]^{2+} \]

Step 2: Calculate oxidation state of cobalt.
Let oxidation state be \(x\). \[ x+0+0-1=+2 \] \[ x=+3 \] Thus cobalt is in the +3 oxidation state.

Step 3: Name the ligands.
\[ NH_3 \rightarrow \text{ammine} \] \[ H_2O \rightarrow \text{aqua} \] \[ Cl^- \rightarrow \text{chlorido} \] Therefore ligand name becomes \[ \text{tetraammineaquachlorido} \]

Step 4: Write the complete name.
\[ {\text{Tetraammineaquachloridocobalt(III) chloride}} \]