question_answer 7)

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

Answer:

In both cases, Fe is oxidation state +3. Outer electronic configuration of Fe3+ is In presence of CN?1, the 3d-electrons pair upleaving only one unpaired electrons. The hybridisation involved is d2sp3 forming inner orbital complex which is weakly paramagnetic. In present to H2O (a weak ligand), 3d-electrons do not pair up. The hydridisation involved is sp3d2 forming an outer orbital complex. As it contains five unpaired electrons, it is strongly paramagnetic.