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

Hint:

The [CoF₆]³⁻ complex is octahedral, sp³d² hybridised, high spin, with Co in +3 oxidation state and coordination number 6.

Answer 1

The Correct Option is B

Let's analyze the given statements about the \([\text{CoF}_{6}]^{3-}\) ion to determine which are true: 

1. The complex \([\text{CoF}_{6}]^{3-}\) has octahedral geometry. This is because the complex is formed with six ligands around the central cobalt ion, which typically leads to an octahedral arrangement. Hence, statement I is true.
2. The coordination number refers to the number of ligand atoms that bind to the central metal atom. Here, Co is surrounded by 6 fluoride ions. Therefore, the coordination number is 6, not 3 as stated, and the oxidation state of Co can be determined by noting that F is a -1 ligand: \(x + 6(-1) = -3\), solving gives \(x = +3\). Hence, statement II is false.
3. The hybridization of central metal atom in this complex is sp³d². Since fluoride is a weak field ligand, Co remains in a high spin state, needing orbitals from both d and sp levels to accommodate them. Hence, statement III is true.
4. This complex is expected to be a high spin complex because fluoride is a weak field ligand, which doesn't cause pairing of electrons. Thus, statement IV is true.

Based on the above analysis, the correct statements are I, III, and IV. Therefore, the correct answer is: I, III and IV.