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 ]
A. A
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 hence it will be diamagnetic. So, \( [ Mn ( NH _3 ) 6 ]^ 3+ \) : Paramagnetic \( [ MnCl _6 ]^ 3- \) : Paramagnetic \( [ FeF _6 ]^ 3- \) : Paramagnetic \( [ CoF _6 ]^ 3- \) : Paramagnetic \( [ Fe ( NH _3 )_6 ]^ 3+ \) : Paramagnetic \( [ Co ( en )_3 ]^ 3+ \) : Diamagnetic Only 1 complex is diamagnetic.
Related: Chemistry — Coordination Compounds · All PYQ Banks