Among the following complexes, the total number of diamagnetic species is_____ [ Mn ( NH ₃ )₆ ]³⁺, [ MnCl ₆ ]³⁻, [ FeF ₆ ]³⁻, [ CoF ₆ ]³⁻, [ Fe ( NH ₃ )₆ ]³⁺ , and [ Co ( en )₃ ]³⁺ [Given, atomic number: Mn =25, Fe =26, Co =27 ; en .= H ₂ NCH ₂ CH ₂ NH ₂ ]

Step-by-step solution

Mn ³⁺ [ Ar ] 3 ~d ^4 d ^4 configuration in t _ 2 ~g and eg _ g orbitals will always have unpaired electrons irrespective of SFL and WFL. Fe ³⁺ [ Ar ] 3 ~d ^5 d ^5 configuration will also have unpaired electron irrespective of SFL and WFL. Co ³⁺ [ Ar ] 3 ~d ^6 d ^6 it can be both paramagnetic or diamagnetic based on field of ligands. In case of F ⁻ weak field ligand, configuration will be t _ 2 ~g ^4 e _ g ^2 hence it is paramagnetic but in case of en strong filed ligand, configuration will be t _ 2 ~g ^6 e _ g ^0 h