The spin-only magnetic moment of an octahedral complex is found to be 15 B.M. Which of the following complexes exhibits this magnetic moment?

Step-by-step solution

The spin-only magnetic moment is given by = n(n+2) B.M., where n is the number of unpaired electrons. Given = 15 B.M., we have n(n+2) = 15 , which gives n = 3 . Let us evaluate the number of unpaired electrons for each complex: For [Mn(CN)₆ ]³⁻ : Mn is in +3 oxidation state ( 3d^4 ). CN^- is a strong field ligand, so the configuration is t_ 2g ^4 e_g^0 . Number of unpaired electrons n = 2 . For [Fe(CN)₆ ]³⁻ : Fe is in +3 oxidation state ( 3d^5 ). CN^- is a strong field ligand, so the configuration is t_ 2g ^5 e_g^0