Question

Which of the following statements are true about [CoF₆]^3- ion?
I. The complex has octahedral geometry.
II. Coordination number of Co is 3 and oxidation state is + 6.
III. The complex is sp³d² hybridised.
IV. It is a high spin complex.

• A. I,II and IV
• B. I,III and IV
• C. II and IV
• D. II,III and IV

Answer 1

The Correct Option is B

• I. The complex has octahedral geometry: This statement is false for [CoF₆]³⁻. The geometry of this complex is octahedral only if it has a coordination number of 6, but the correct coordination number in this case is 3 (as per statement II).
• II. Coordination number of Co is 3 and oxidation state is +6: This statement is false. The oxidation state of Co in [CoF₆]³⁻ is +3, and the coordination number is 6, not 3.
• III. The complex is sp³d² hybridised: This statement is true. Since the complex has a coordination number of 6, the cobalt ion uses sp³d² hybridisation for octahedral geometry.
• IV. It is a high spin complex: This statement is true for [CoF₆]³⁻. Since it is a 3d⁶ configuration and in the absence of strong field ligands like F⁻, it forms a high spin complex.

Therefore, the correct answer is (B) I, III, and IV.