Exams and Assignments
Due April 19th, 2001
1. Explain why octahedral complexes of Cr(III) undergo ligand substitution much slower than corresponding complexes of Fe(III). (15 points)
2. The complex [Fe(ethylenediamine)3]2+ is paramagnetic but [Fe(1,10-phenanthroline)3]2+ is diagmagnetic, why? (10 points).
3. Dissolution of Fe(III) perchlorate in acidic solution (pH = 1) results in a pale violet colored solution, which changes to an intense yellow-brown color as the pH is increased to 4 or 5. Explain this observation (15 points).
4. You have been provided with a sample of a supposedly "inert" Cr(III) complex, [Cr(III)L5X]. However, upon addition of a new ligand Y you observe rapid ligand exchange to form [Cr(III)L5Y]. You find that in addition to the Cr(III) complex there is a trace of Cr(II) in solution. Explain why ligand exchange for the octahedral Cr(III) is rapid. (20 points).
5. Why is the trans effect order of ligands essentially the same as the trans influence for octahedral complexes, but the series are nearly reversed for square planar complexes? (10 points).