Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: The spin only magnetic moment value for Fe(CN)$$_6^{3-}$$ is 1.74 BM, whereas for [Fe(H$$_2$$O)$$_6$$]$$^{3+}$$ is 5.92 BM.
Reason B: In both complexes, Fe is present in +3 oxidation state.
In the light of the above statements, choose the correct answer from the options given below:

Assertion A: The spin-only magnetic moment for $$[Fe(CN)_6]^{3-}$$ is 1.74 BM, whereas for $$[Fe(H_2O)_6]^{3+}$$ is 5.92 BM.

Fe³⁺ has the electronic configuration [Ar]3d⁵ (5 d-electrons).

In $$[Fe(CN)_6]^{3-}$$: CN⁻ is a strong field ligand, causing pairing. The configuration is $$t_{2g}^5 e_g^0$$ with 1 unpaired electron.

$$\mu = \sqrt{n(n+2)} = \sqrt{1(3)} = 1.73 \approx 1.74$$ BM ✓

In $$[Fe(H_2O)_6]^{3+}$$: H₂O is a weak field ligand, no pairing occurs. The configuration is $$t_{2g}^3 e_g^2$$ with 5 unpaired electrons.

$$\mu = \sqrt{5(7)} = \sqrt{35} = 5.92$$ BM ✓

So Assertion A is true.

Reason R: In both complexes, Fe is in +3 oxidation state. This is true.

However, the same oxidation state does not explain the different magnetic moments. The difference arises because of the different ligand field strengths (strong vs weak field ligands), not the oxidation state. Therefore, R is NOT the correct explanation of A.

The correct answer is Both A and R are true but R is NOT the correct explanation of A.