Among the following, the pair of paramagnetic complexes is

Step-by-step solution

K 3 Fe CN 6 Central metal ion is Fe 3 + , which has Ar 3 d 5 configuration as free ion. In strong ligand field of CN - , its splits to become t 2 g e g 0 5 . One unpaired electron will be there, and ∴ It is paramagnetic. K 3 CoF 6 : Central metal ion is Co 3 + . Free metal ion configuration Ar 3 d 6 . In weak ligand field of F - , its splits and becomes t 2 g 4 e g 2 . Four unpaired electrons, therefore paramagnetic. In K 4 Fe CN 6 , central ion is Fe 2 + and in Co NH 3 6 Cl 3 , central ion is Co 3 + In both of the