Question

dulude cds Reat wofh At the end of reaction IV, the ligand around Cu is HO, In reaction V the NH, replaces the H2O. Which ligand-metal bond is stronger and why? (Cu (II) to H2O or Cu (II) to NH,?) . After reaction VI, the ligand on copper is now H2O (again). This seems to contradict the result of question 3. What does the H2SO4 do such that NH3 is no longer an effective ligand for Cu(II)? Why is the "NH3 treated with H2SO." no longer a good ligand?

Answer 1

3. The bond Cu-NH₃ is stronger. This is why the NH₃ ligand is able to displace the H₂O. The reason lies in the fact that N is the better electron pair donor as compared to O.

4. The reaction that takes place is : NH₃ + H⁺ $\rightarrow$ NH₄⁺

Now NH₄⁺ is not a good ligand at all because it no longer has an electron pair to donate to Cu. Therefore, it is replaced by H₂O being the stronger ligand in this case