A transition metal complex is observed to have a spin-only magnetic moment of 4.90 B.M. Which of the following complexes corresponds to 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 = 4.90 B.M., we have n(n+2) = 4.90 , which gives n = 4 . Let us evaluate the number of unpaired electrons for each complex: [Co(NH₃)₆]³⁺ : Cobalt is in +3 oxidation state ( d^6 ). Since NH₃ acts as a strong field ligand for Co³⁺ , it forms a low-spin complex ( t_ 2g ^6 e_g^0 ). Number of unpaired electrons n = 0 . [Mn(CN)₆]³⁻ : Manganese is in +3 oxidation state ( d^4 ). CN^- is a strong field ligand, forming