Selective stabilization of transition state structures for cope rearrangements of semibullvalene and barbaralane through interactions with halogens

Journal of Physical Chemistry A

Volumn 111, Issue 30, 2007, Pages 7149-7153

  Wang, Selina C ^a   Tantillo, Dean J ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

COMPLEXATION; HALOGEN COMPOUNDS; PARAFFINS; QUANTUM CHEMISTRY;

BARBARALANE; SELECTIVE STABILIZATION; SEMIBULLVALENE; TRANSITION STATE STRUCTURES;

OLEFINS;

EID: 34548263201     PISSN: 10895639     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp0724525     Document Type: Article

References (38)

1. For leading references, see: (a) Williams, R. V. Eur. J. Org. Chem. 2001, 227-235.
2. (b) Williams, R. V. Chem. Rev. 2001, 101, 1185-1204.
3. (c) Doering, W. v. E.; Ferrier, B. M.; Fossel, E. T.; Hartenstein, J. H.; Jones, M., Jr.; Klumpp, G.; Rubin, R. M.; Saunders, M. Tetrahedron 1967, 23, 3943-3963.
4. (a) Hoffmann, R.; Stohrer, W.-D. J. Am. Chem. Soc. 1971, 93, 6941-6948.
5. (b) Dewar, M. J. S.; Lo, D. H. J. Am. Chem. Soc. 1971, 93, 7201-7207.
6. (c) Williams, R. V.; Kurtz, H. A. J. Am. Chem. Soc. 1988, 53, 3626-3628.
7. Seefelder, M.; Heubes, M.; Quast, H.; Edwards, W. D.; Armantrout, J. R.; Williams, R. V.; Cramer, C. J.; Goren, A. C.; Hrovat, D. A.; Borden, W. T. J. Org. Chem. 2005, 70, 3437-3449.
8. See also: Quast, H.; Seefelder, M.; Becker, C.; Heubes, M.; Peters, E.-M.; Peters, K. Eur. J. Org. Chem. 1999, 2763-2779.
9. (a) using boron: Wu, H. S.; Jiao, H.; Wang, Z.-X.; Schleyer, P. v. R. J. Am. Chem. Soc. 2003, 125, 10524-10525.
10. (b) using phosphorous (for barbaralane): Reiher, M.; Kirchner, B. Angew. Chem., Int. Ed. 2002, 41, 3429-3433.
11. 2v symmetry: Dai, S.; Wang, J. T.; Williams, F. J. Am. Chem. Soc. 1990, 112, 2835-2837.
12. Jiao, H.; Nagelkerke, R.; Kurtz, H. A.; Williams, R. V.; Borden, W. T.; Schleyer, P. v. R. J. Am. Chem. Soc. 1997, 119, 5921-5929.
13. Tantillo, D. J.; Hoffmann, R.; Houk, K. N.; Warner, P. M.; Brown, E. C.; Henze, D. K. J. Am. Chem. Soc. 2004, 126, 4256-4263.
14. Jiao, H.; Schleyer, P. v. R. Angew. Chem., Int. Ed. Engl. 1993, 32, 1760-1763.
15. Wang, S. C.; Tantillo, D. J. Eur. J. Org. Chem. 2006, 738-745 (note, in particular, reference 15 therein).
16. (a) All geometries were optimized using B3LYP/6-31G(d) (Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652;
17. Becke, A. D. J. Chem. Phys. 1993, 98, 1372-1377.
18. Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785-789.
19. Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F.; Frisch, M. J. J. Phys. Chem. 1994, 98, 11623-11627) as implemented in GAUSSIAN03 (Frisch, M. J.; et al. Gaussian, Inc.: Pittsburgh, PA, 2003; see Supporting Information for full reference).
20. 2O, and HCN can be found in the Supporting Information; in general, it appears that B3LYP/6-31G(d) slightly overestimates absolute binding energies for these species. All stationary points were characterized as minima or transition structures by analyzing their vibrational frequencies.
21. All reported energies include zero-point energy corrections from frequency calculations, scaled by 0.9806 (Scott, A. P.; Radom, L. J. Phys. Chem. 1996, 100, 16502-16513).
22. In some cases, the effects of solvent were modeled using CPCM calculations (with UAKS radii), a self-consistent reaction field (SCRF) method (Barone, V.; Cossi, M. J. J. Phys. Chem. A 1998, 102, 1995-2001.
23. Barone, B.; Cossi, M.; Tomasi, J. J. Comput. Chem. 1998, 19, 404-417).
24. Structural drawings were produced using Ball & Stick (Müller, N., Falk, A. Ball & Stick V.3.7.6, Molecular Graphics Application for MacOS Computers; Johannes Kepler University: Linz, Austria, 2000.).
25. (b) The Amsterdam Density Functional (ADF) Program was also used to calculate and analyze the binding energies between semibullvalene and various halogens. The B3LYP functional with the triple-zeta doubly polarized (TZ2P) basis set was used as implemented in ADF2006 (Scientific Computing & Modeling, NV, Amersterdam). See Supporting Information for further details. For a general description of ADF, see: Bickelhaupt, F. M.; Baerends, E. J. Rev. Comput. Chem. 2000, 15, 1-86.
26. 2, the delocalized structure is a minimum with MP2/6-31G(d). See Supporting Information for further details.
27. 3, BrOH, and ClOH, in the hopes that, if delocalized minima could be located for such species, halogen atoms could be covalently tethered to the semibullvalene framework to produce delocalized species stabilized through intramolecular interactions. Unfortunately, no delocalized minima were located for these species. Barrierlowering upon complexation was still observed, however. See Supporting Information for details.
28. Absolute gas phase complexation energies (with and without BSSE) can be found in the Supporting Information. Binding energies (both enthalpies and free energies) were generally small, but in some cases were larger than 5 kcal/mol. For example, the localized structures in Figure 2a,b are not predicted to be bound based on computed free energies of binding at 300 K, but the more delocalized structures in Figures 1 and 2c,d are predicted to be bound by 2.4, 0.7, and 1.2 kcal/mol, respectively; i.e. more delocalized structures are more tightly bound.
29. The structure shown in Figure 2b is much less symmetrical than those in Figures 1 and 2a,c,d; yet this structure corresponds to a minimum even with tightened convergence criteria. Constraining the C-Br distances to 3.1 Å and allowing the rest of the structure to relax leads to a (non-minimum) structure that is only 0.4 kcal/mol higher in energy than the optimized structure, however, suggesting that the energy surface in this area is very flat.
30. 2O. See Supporting Information for details.
31. Note that the computed HOMO (resembling the structure at the right of Chart la) and HOMO-1 (left in Chart la) for uncomplexed semibullvalene are close in energy (-0.179 and -0.235 eV, respectively, at the B3LYP/6-31G(d) level). The LUMO (left in Chart la) and LUMO-1 (right in Chart la) for uncomplexed semibullvalene are also close in energy (-0.006 and +0.029 eV, respectively).
32. (a) The electrostatic contribution is computed to be 15.2 kcal/mol while the orbital interaction contribution is computed to be 17.2 kcal/mol. Details on complexes with other halogens can be found in the Supporting Information.
33. (b) Nucleus-independent chemical shift (NICS) values (Chen, Z.; Wannere, C. S.; Corminboeuf, C.; Puchta, R.; Schleyer, P. v. R. Chem. Rev. 2005, 105, 3842-3888) for the various complexes with delocalized semibullvalene can also be found in the Supporting Information; these values are almost always close to -18 (GIAO-B3LYP/6-31G(d)), indicating that the aromaticity of uncomplexed delocalized semibullvalene (NICS value of -14 at same level) is not disrupted upon complexation.
34. With FBr and FCl, in addition to complexes like those shown for BrCl, complexes were located with these mixed halogens pointing "up" rather than "down" (as in the structures shown in the text). See Supporting Information for further details.
35. 2v symmetry; yet this structure appears to be a minimum. Constraining all four C-Br distances to 3.1 Å and allowing the rest of the structure to relax leads to a structure that is only 0.04 kcal/mol higher in energy than the optimized structure, however.
36. 3 complexes shown in Figure 6 were also optimized in dichloromethane; in this case, the barriers were found to be 5.5 and 4.2 kcal/mol.
37. 3 complexes analogous to those shown in Figure 6 were also located; in this case, the barriers were 4.2 and 4.5 kcal/mol in the gas phase.
38. 3 complexes analogous to those shown in Figure 6 were also located; in this case, the barriers were 4.2 and 4.2 kcal/mol in the gas phase. See Supporting Information for additional details.