Which one of the following has lowest value of magnetic behaviour? — Coordination Compounds Chemistry Question

💡 Solution & Explanation

Step 1: Basicity or value of magnetic behavior is determined by the number of unpaired electrons (n) in each complex. Step 2: Since CN^- is a strong-field ligand, it forms low-spin complexes: Cr^3+ (3d^3) has n = 3; Mn^3+ (3d^4) has n = 2; Fe^3+ (3d^5) has n = 1. Step 3: Co^3+ (3d^6) in [Co(CN)6]^3- forms a highly stable low-spin complex with all electrons paired in the t_2g orbitals (t_2g^6 eg^0), resulting in n = 0 unpaired electrons (diamagnetic). Thus, option (d) has the lowest value.