Chemistry - Coordination Chemistry Question with Solution | TestHub

(i), (iii), (iv) are change

The complex is ${\left[\mathrm{Co}(\mathrm{en}{)}_3\right]}^{3+}$. When 'en' (ethylenediamine, a bidentate neutral ligand) is replaced by 'gly' (glycinate, a bidentate anionic ligand, ${\mathrm{NH}}_2{\mathrm{CH}}_2{\mathrm{COO}}^{-}$), the new complex is $\left[\mathrm{Co}(\mathrm{gly}{)}_3\right]$.

(i) $\Delta$ (splitting energy): 'en' is a stronger field ligand than 'gly'. Therefore, $\Delta$ will change.

(ii) EAN value: The oxidation state of Co remains +3. The coordination number remains 6. EAN = Z - oxidation state + 2 * coordination number. EAN = 27 - 3 + 2 * 6 = 36. This does not change.

(iii) Geometrical isomers: ${\left[\mathrm{Co}(\mathrm{en}{)}_3\right]}^{3+}$ has no geometrical isomers (only fac/mer for ${\mathrm{MA}}_3{\mathrm{B}}_3$ type). $\left[\mathrm{Co}(\mathrm{gly}{)}_3\right]$ can exist as fac and mer isomers. So, geometrical isomers change.

(iv) Stereoisomers: Both complexes are octahedral and can exhibit optical isomerism (enantiomers). The number of stereoisomers for ${\left[\mathrm{Co}(\mathrm{en}{)}_3\right]}^{3+}$ is 2 (d and l forms). For $\left[\mathrm{Co}(\mathrm{gly}{)}_3\right]$, there are 2 fac enantiomers and 1 mer diastereomer (which is achiral). Thus, the total number of stereoisomers changes.

(v) Magnetic moment: Both 'en' and 'gly' are strong field ligands for ${\mathrm{Co}}^{3+}$ (d⁶ system), leading to low spin complexes. Thus, both complexes will be diamagnetic with zero unpaired electrons and zero magnetic moment. This does not change.

(vi) Number of 'd' orbitals participating in hybridization: Both are low spin ${\mathrm{Co}}^{3+}$ (d⁶) complexes with octahedral geometry, so they undergo ${\mathrm{d}}^2{\mathrm{sp}}^3$ hybridization. Two 'd' orbitals participate. This does not change.

Properties that change are (i), (iii), (iv).

The final answer is 3.