Question

[Fe(H2O)6]3+ is strongly paramagnetic whereas [Fe(CN)6]3− is weakly paramagnetic. Explain.

Answer 1

Explanation:

In the presence of CN- the three d electron pair up, it  leaves only one unpaired electron. The hybridization is d²sp³ which forms an  inner orbital complex.

In the presence of H20 three d electrons they do not pair up. The hybridization is sp³d² forming an outer orbital complex which consists of five unpaired electron and is strongly paramagnetic

This is due to the fact that H2o is a weak field ligand that forms only the high spin complexes. In Zn[Fe(H2o)6] 3+ there are five paired electrons whereas in [Fe(CN)6]3- there is only one paired electron.