Question

Which formula and name combination is INCORRECT ?

• A. K₃[Al(C₂O₄)₃] - Potassium trioxalatoaluminate (III)
• B. [Pt(NH₃)₂ Cl(NO₂)]- Diamminechloridonitrito - N - platinum (II)
• C. [CoCl₂(en)₂]Cl - Dichloridodiethylenediammine cobalt (II) chloride
• D. [Co(NH₃)₄ (H₂O)Cl]Cl₂ - Tetraammineaquachloridocobalt (III) chloride

Answer 1

The Correct Option is C

1. K3[Al(C2O4)3] - Potassium trioxalatoaluminate (III)

• The formula is correct.
• The name is correct. C2O4 is oxalate, and it's a tridentate ligand. Al has a +3 oxidation state.

2. [Pt(NH3)2 Cl(NO2)]- Diamminechloridonitrito - N - platinum (II)

• The formula is correct.
• The name is correct. NH3 is ammine, Cl is chlorido, NO2 is nitrito-N, and Pt has a +2 oxidation state.

3. [CoCl2(en)2]Cl - Dichloridodiethylenediammine cobalt (II) chloride

• This formula and name combination is INCORRECT.
• The correct name should be: Dichloridobis(ethylenediamine)cobalt(III) chloride.
  • 'en' is ethylenediamine, which is a neutral bidentate ligand.
  • The oxidation state of Co is +3, not +2.
  • The prefix 'bis' is used for bidentate ligands.

4. [Co(NH3)4 (H2O)Cl]Cl2 - Tetraammineaquachloridocobalt (III) chloride

• The formula is correct.
• The name is correct. NH3 is ammine, H2O is aqua, Cl is chlorido, and Co has a +3 oxidation state.

Conclusion:

The incorrect formula and name combination is Option 3.

The correct answer is Option 3.

Answer 2

In coordination chemistry, the naming of a complex compound follows certain rules. Let’s analyze each option:

(A) K₃[Al(C₂O₄)₃] – Potassium trioxalatoaluminate (III): This is correct. The complex has three oxalate ligands, and the central metal is aluminum with an oxidation state of +3.

(B) [Pt(NH₃)₂Cl(NO₂)] – Diamminelchloridonitrato – N – platinum (II): This is correct. The platinum (Pt) is in the +2 oxidation state, and the ligands are ammonia (NH₃), chloride (Cl), and nitrito (NO₂) in the N-bonding mode.

(C) [CoCl₂(en)₂]Cl – Dichloridoethylenediamine cobalt (II) chloride: This is incorrect. The formula [CoCl₂(en)₂]Cl should be named as "Dichloridoethylenediamine cobalt (III) chloride" because the cobalt ion is in the +3 oxidation state (not +2 as suggested in the name). The oxidation state of the metal should match the formal charge of the complex, which is +3 for cobalt in this case.

(D) [Co(NH₃)₄(H₂O)Cl]Cl₂ – Tetraamminaquachloridocobalt (III) chloride: This is correct. The cobalt is in the +3 oxidation state, and the ligands are ammonia (NH₃), water (H₂O), and chloride (Cl).

Therefore, option (C) has the incorrect naming, and the correct answer is (C).