All references are to J. Am.Chem. Soc., 2019, 141.
1. C. S. Anstöter, J. P. Rogers, and J. R. R. Verlet (p. 6132 – 6135) determined the anion-π bond strength of iodide ion with hexafluorobenzene using photoelectron spectroscopy. They find that the anion-π bond strength is 51 kJ/mol. How does this compare to a classical calculation? If there is a significant difference, provide an explanation. For C6F6 the dipole moment is 0 D and the polarizability is 9.58 Å3.
2. G. Yan, T. Wähler, R. Schuster, M. Schwarz, C. Hohner, K. Werner, J. Libuda, and P. Sautet (p. 5623 – 5627) investigated the interaction of water with the surface of Co3O4, which can be used as a heterogeneous redox catalyst. What is the oxidation of the cobalt in this oxide? Given this oxidation state, is it reasonable that oxide can act as a redox catalyst? Why or why not? Surface cobalt ions are in a C3v local environment. Which type of holes does this imply the cobalt ions occupy in the bulk? When the surface is exposed to water, how many water molecules would you expect to bind to each cobalt ion? Explain your reasoning.
3. H. Wang, V. C. Jordan, I. A. Ramsay, M. Sojoodi, B. C. Fuchs, K. K. Tanabe, P. Caravan, and E. M. Gale (p. 5916 – 5925) studied a redox active iron complex, shown below, as an MRI contrast reagent (requiring a magnetic moment). Predict the spin-only magnetic moment for the two oxidation states shown in units of Bohr-magnetons. The anion is a poorer contrast agent than the neutral molecule. Is this consistent with your estimates of the magnetic moment? Why or why not?
4. N. A. Hirscher, D. P. Sierra, and T. Agapie (p. 6022 – 6029) developed ethylene oligomerization catalysts using chromium complexes. In comparing the complexes shown below, the authors assert that I is too stable for catalysis, III is too reactive, and II is “just right”. What bonding theory best supports their assertions. Explain your reasoning.
5. S. Tian, J.-F. Zhang, C. Li, T. Ying, S. Li, X. Zhang, K. Liu, and H. Lei (p. 5326 – 5333) measured the magnetic and structural properties of VI3. The structure shows that the vanadium ion is surrounded by six iodides in Oh symmetry. At high temperature the magnetic susceptibility follows the Curie-Weiss law. Predict the room temperature (300 K) magnetic moment and paramagnetic susceptibility. At 50 K there is a sharp increase in the magnetic susceptibility and at 2 K the magnetic susceptibility is strongly hysteretic. Explain what happens to the magnetic properties below 50 K.
6. Z. Wu, C. Chen, J. Lie, Y. Lu, J. Xu, X. Liu, G. Cui, T. Trabelsi, J. S. Francisco, A. Mardyukov, A. K. Eckhardt, P. R. Scheiner, and X. Zeng (p. 3361 – 3365) followed the photolytic decomposition of S-nitrosothiols, H3CSNO. Draw the Lewis dot structure for this compound and predict all of the bond angles.
7. J. J. Moreno, M. F. Espada, J. Campos, J. López-Serrano, S. A. Macgregor, and E. Carmona (p. 2205 – 2210) used (η5-C5Me5)(PMe2Ar)Ir(III), shown below, to activate C-H bonds. How must the phenyl ring shown in red be bonded to the Ir for the complex to be stable?
8. S. Kundu, P. N. Phu, P. Ghosh, S. A. Kozimor, J. A. Bertke, S. C. E. Stieber, and T. H. Warren (p. 1415 – 1419) examined linkage isomerization in the nickel β-diketiminato complex shown below. The visible spectrum of the complex showed a single peak at 615 nm with ε = 150 M–1cm–1. What is the oxidation state of the nickel? Is this consistent with the visible spectrum? Why of why not? What is the value for 10Dq (in units of cm–1)?
9. E. Hayashi, Y. Yamaguchi, K. Kamata, N. Tsunoda, Y. Kumagai, F. Oba, and M. Hara (p. 890 – 900) found that the crystal structure of MnO2 affected the catalytic activity for oxidation. In the β-phase the crystal structure is approximately the same as fluorite (where the cation is 4-coordinate, the anion is 8-coordinate, and M = 2.519) while the γ-phase is approximately the same as the rutile structure (where the cation is 6-coordinate, the anion is 3-coordinate, and M = 2.408). Estimate the lattice energy for each phase in units of kJ/mole. For one example oxidation the ratio of the catalysis is 28/5 for β-phase to γ-phase. Is the difference accounted for by the difference in lattice energy? Why or why not?
