Which statement is correct concerning [CoF6]3-?
a) This is a high-spin complex.
b) F- is a strong field ligand.
c) The energy difference between the d orbitals, Δ, is large.
d) The complex is diamagnetic.
a) This is a high-spin complex.
To determine which statement is correct concerning [CoF6]3-, let's analyze each option step by step:
a) This is a high-spin complex.
The spin state of a complex depends on the number of unpaired electrons in the d-orbitals of the central metal ion. In a high-spin complex, the electrons occupy the higher energy orbitals first before pairing up. To determine the spin state, we need to know the electron configuration of the central metal ion.
For cobalt (Co), the electron configuration is [Ar] 4s^2 3d^7. Since there are seven d-electrons, the coordination number of the complex is 6 (CoF6), and each fluoride ion (F-) donates one electron, the electron configuration becomes T2g^5 Eg^2. As there are three unpaired electrons, [CoF6]3- is a high-spin complex.
Therefore, statement a is correct.
b) F- is a strong field ligand.
The strength of the ligand determines how it interacts with the d-orbitals of the metal ion. Strong field ligands cause a larger energy difference between the t2g and eg sets of d-orbitals (Δ), favoring the pairing of electrons.
F- is a small and highly electronegative ligand, making it a strong field ligand. Therefore, statement b is correct.
c) The energy difference between the d orbitals, Δ, is large.
As mentioned in option b, strong field ligands cause a larger energy difference between the t2g and eg sets of d-orbitals (Δ). Since F- is a strong field ligand, the energy difference Δ is indeed large.
Therefore, statement c is correct.
d) The complex is diamagnetic.
To determine the magnetic nature of a complex, we analyze the number of unpaired electrons. In a diamagnetic complex, all the electrons are paired.
Since [CoF6]3- has three unpaired electrons, it is not diamagnetic.
Therefore, statement d is incorrect.
In conclusion, statements a, b, and c are correct concerning [CoF6]3-.