The complex having the highest spin only magnetic moment is

Step-by-step solution

The spin only magnetic moment for a complex can be calculated using formula μ = n n + 2 (a) Fe CN 6 3 - The oxidation number Fe in Fe CN 6 3 - is + 3 .The electronic configuration of Fe 3 + is - Ar 3 d 5 4 s 0 As CN - is a strong ligand pairing will occur. Fe CN 6 3 - ∴ n = 1 ⇒ μ = 1 1 + 2 = 3 (b) Fe H 2 O 6 2 + The oxidation number of Fe in Fe H 2 O 6 2 + is + 2 .The electronic configuration of Fe 2 + is - Ar 3 d 6 4 s 0 As H 2 O is weak ligand, so pairing will not occur. Fe H 2 O 6 2 - n = 4 μ = 4 4 + 2 = 24 (c)