Question

The hypothetical complex chloro diaquatriammine cobalt (III) chloride can be represented as 

• A. [CoCl(NH₃)₃(H₂O)₂]Cl₂
• B. [Co(NH₃)₃(H₂O)Cl₃]
• C. [Co(NH₂)3(H₂O)₂Cl]
• D. [Co(NH₃)₃(H₂O)₃Cl₃]

Answer 1

The Correct Option is A

To determine the correct representation of the given complex compound "chloro diaquatriammine cobalt (III) chloride," we need to understand the nomenclature and structure of coordination compounds.

1. Nomenclature Analysis:
   • The term "chloro" indicates the presence of chloride ions within the coordination sphere or outside as anionic counter ions.
   • "Diaquatriammine" specifies that there are 2 water molecules (aqua) and 3 ammonia molecules (ammine) coordinated to the central metal atom.
   • "Cobalt (III)" indicates that the oxidation state of cobalt is +3.
   • The term "chloride" suggests the presence of chloride ions outside the coordination sphere, balancing the charge of the complex.
2. Analyzing Options:
   • Option 1: [CoCl(NH₃)₃(H₂O)₂]Cl₂
     • The coordination sphere has 1 chloride, 3 ammonia, and 2 water molecules. This matches "chloro diaquatriammine."
     • There are 2 chloride ions outside the sphere, matching the oxidation state of +3 for cobalt since the coordination sphere has a net charge of +1.
     • This option correctly represents the compound.
   • Option 2: [Co(NH₃)₃(H₂O)Cl₃]
     • This suggests 3 chloride ions within the coordination sphere, which does not match the "chloro" (implying one chloride) description.
   • Option 3: [Co(NH₂)₃(H₂O)₂Cl]
     • "(NH₂)" indicates an error because it refers to an amide ion, not ammonia.
   • Option 4: [Co(NH₃)₃(H₂O)₃Cl₃]
     • This suggests 3 chlorides and 3 water molecules within the sphere, which does not match the "diaqua" and "chloro" description.
3. Conclusion: Based on the analysis above, the correct representation of the compound "chloro diaquatriammine cobalt (III) chloride" is indeed [CoCl(NH₃)₃(H₂O)₂]Cl₂ (Option 1). It correctly follows the IUPAC naming conventions and the molecular structure requirements described.