Is the Mills-Nixon Effect Real?

Journal of the American Chemical Society

Volumn 113, Issue 22, 1991, Pages 8277-8280

  Stanger, Amnon ^a  

^a TECHNION ISRAEL INSTITUTE OF TECHNOLOGY   (Israel)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000026440     PISSN: 00027863     EISSN: 15205126     Source Type: Journal    
DOI: 10.1021/ja00022a012     Document Type: Article

References (46)

1. Mills, W. H.; Nixon, I. G. J. Chem. Soc. 1930, 2510.
2. Longust-Higgins, H. L.; Coulson, C. A. Trans. Faraday Soc. 1946, 42, 756.
3. Chung, C. S.; Cooper, M. A.; Manatt, S. L. Tetrahedron 1971, 27, 701.
4. Halton, B.; Halton, M. P. Tetrahedron 1973, 29, 1717.
5. Mahanti, M. K. Indian J. Chem. 1980, 19B, 149.
6. Hiberty, P. C.; Ohanessian, G.; Delbecq, F. J. Am. Chem. Soc. 1985, 107, 3095.
7. Apeloig, Y.; Arad, D.; Halton, B.; Randell, C. J. J. Am. Chem. Soc. 1986,108, 4932.
8. Apeloig, Y.; Arad, D. J. Am. Chem. Soc. 1986, 108, 3241.
9. Dewar, M. J. S.; Holloway, U. K. J. Chem. Soc., Chem. Commun. 1984, 1188. This paper presents MNDO calculations of tricyclopropabenzene (6) and finds a strong Mills-Nixon effect. However, MNDO tends to overemphesize bond fixation, as is evident from our calculations of 2 and 3 (unpublished). See also ref 1h.
10. Eckert-Maksić, M.; Hodošcek, M.; Kovaček, D.; Mitić, D.; Maksić, Z. B.; Poljanec, K. J. Mol. Struct. 1990, 206, 89 and references therein.
11. Maksić, Z. B. Manuscripts in preparation.
12. For example: Mitchell, R. H.; Slowey, P. D.; Kamada, T.; Williams, R. V.; Garratt, P. J. J. Am. Chem. Soc. 1984, 106, 2431 and ref 4 therein.
13. Diercks, R.; Vollhardt, K. P. C. J. Am. Chem. Soc. 1986, 108, 3150.
14. Shaik, S. S.; Hiberty, P. C.; Ohanessian, G.; Lefour, J.-M. J. Phys. Chem. 1988, 92, 5068.
15. Shaik, S. S.; Hiberty, P. C.; Ohanessian, G.; Lefour, J.-M. J. Am. Chem. Soc. 1987, 109, 363.
16. Shaik, S. S.; Hiberty, P. C. J. Am. Chem. Soc. 1985, 107, 3089.
17. Hiberty, P. C.; Shaik, S. S.; Lefour, J.-M.; Ohanessian, G. J. Org. Chem. 1985, 50, 4657.
18. Shaik, S. S.; Bar, R. Nouv. J. Chim. 1984, 8, 411.
19. Shaik, S. S.; Hiberty, P. C.; Ohanessian, G. Lefour, J.-M. Nouv. J. Chim. 1985, 9, 385.
20. For opposing views, see for example: Baird, N. C. J. Org. Chem. 1986, 51, 3907.
21. Weinhold, F.; Glendening, E. D. “How Important is Resonance in Organic Chemistry?”. We are thankful to Professor Weinhold for making the manuscript available to us prior to publication. For papers agreeing with Shaik's views, see.
22. Stanger, A.; Vollhardt, K. P. C. J. Org. Chem. 1988, 53, 4879 and references therein.
23. The concept of rehybridization was introduced to explain the reactivity of strained aromatic compounds. Streitwieser, A.; Zigler, G. R.; Mowery, P. C.; Lewis, A.; Lawler, R. G. J. Am. Chem. Soc. 1968, 90, 1357. However, the authors do not conclude bond fixation (i.e., Mills-Nixon effect) as a result of the rehybridization.
24. Reed, A. E.; Curtis, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899.
25. Each bond length (R1 and R2) shows a good correlation to n. For R,: intercept = 1.143 53, slope = 0.12869, correlation coefficient = 0.999 103. For R2: intercept = 1.08505, slope = 0.158 81, correlation coefficient =0.999917.
26. A reviewer suggested that the C—H bonds in the strained benzene model should also be curved, and I agree that this might indeed be the case. However, due to the smaller flexibility of the hydrogens (see text) within the basis set limitations, the curvature of C—H bonds must be much smaller than the curvature of C—C bonds. Thus, even if the C—H bonds in the bent benzene are somewhat curved, they are taken as a reference for the “pure” strain in this study, and the other systems (which are more flexible) are compared to this model.
27. This study uses the basis set limitations (inflexibility) in order to study pure strain. We do not suggest that real systems behave accordingly. However, due to the nature of the model, we are able to separate the strain from the other factors.
28. Due to crystal packing forces, the structure of 1b is not completely planar (see ref 5). Thus, the measured θ's are 88.10–88.69°.
29. Thummel, R. P.; Korp, J. D.; Bernal, I.; Harlow, R. L.; Soulen, R. L. J. Am. Chem. Soc. 1977, 99, 6916.
30. Cobbledick, R. E.; Einstein, F. W. B. Acta Crystallogr. 1976, B32, 1908.
31. Fluorine has a large effect on the properties of small rings. Two representative examples are given, Bis(trialkylphosphine)-nickel(COD) reacts with cyclopropabenzene to give the insertion or the dimerization products, depending on the phosphine Mynott, R.; Neidlein, R.; Schwager, H.; Wilke, G. Angew. Chem., Int. Ed. Engl. 1986, 25, 367.
32. Neidlein, R.; Rufiñska, A.; Schwager, H.; Wilke, G. Angew. Chem., Int. Ed. Engl. 640. However, when 7,7-difluorocyclopropabenzene is used instead of cyclopropabenzene, the threemembered ring does not open up and only the propellane-type addition product is obtained (Schwager, H.; Kruger, C; Neidlein, R.; Wilke, G. Angew. Chem., Int. Ed. Engl. 1987, 26, 65).
33. However, when 7,7-difluorocyclopropabenzene is used instead of cyclopropabenzene, the threemembered ring does not open up and only the propellane-type addition product is obtained (Schwager, H.; Kruger, C; Neidlein, R.; Wilke, G. Angew. Chem., Int. Ed. Engl. 1987, 26, 65).
34. For a theoretical investigation on the effect of fluorine as a cyclopropane substituent, see: Cremer, D.; Kraka, E. J. Am. Chem. Soc. 1985, 107, 3811 and references therein.
35. For a comprehensive review and data regarding the fluorine effect, see: Smart, B. E. Mol. Struct. Energ. 1986, 3, 141.
36. Even the authors of the paper presenting the structure of 3a (ref 10a) are not sure that the comparison between 3 and 3a is valid because of the same reason.
37. Boese, R.; Blaser, D. Angew. Chem., Int. Ed. Engl. 1988, 27, 304.
38. Apeloig, Y.; Kami, M.; Arad, D. In Strain and Its Implications in Organic Chemistry; de Meijere, A., Blechert, S.; Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1989; pp 457–462.
39. Blaser, D.; Boese, R.; Brett, W. A.; Rademacher, P.; Schwager, H.; Stanger, A.; Vollhardt, K. P. C. Angew. Chem., Int. Ed. Engl. 1989, 28, 206.
40. Bläser, D.; Boese, R.; Brett, W. A.; Rademacher, P.; Schwager, H.; Stanger, A.; Vollhardt, K. P. C. Chem., Int. Ed. Engl. 1990, 29, 1151. The X-ray structure of the molecule reveals that the central ring's bonds are alternating in the same manner as in 1, although the ring has no IT electrons. Thus, Rt = 1.511 Å and R2 = 1.599 Å. Note that R2 in 8 is even longer than the respective bond in cyclobutabenzene (1.576 Å)12 and that ΔR for this molecule (with the saturated ring) is smaller than the respective ΔR for 1 (with the benzenoid ring).
41. Stanger, A.; Vollhardt, K. P. C. J. Org. Chem. 1988, 53, 4879 and references therein.
42. For example: (a) Cyclopropabenzene: Experimental structure determination by Neidlein et al. (Neidlein, R.; Christen, D.; Poignée, V.; Boese, R.; Bläser, D.; Gieren, A.; Ruiz-Pérez, C.; Hübner, T. Angew. Chem., Int. Ed. Engl. 1988, 27, 294) and 3-21G geometry calculated by Apeloig and Arad, ref 1h.
43. 7: Experimental structure determination by Bläser et al.14 and 3-21G geometry calculated by Apeloig et al.13
44. For the preparation of 3, see: (a) Nutakul, W.; Thummel, R. P.; Taggart, A. D. J. Am. Chem. Soc. 1979, 101, 770.
45. Heilbronner, E.; Kovać, B.; Nutakul, W.; Taggart, A. D.; Thummel, R. P. J. Org. Chem. 1981, 46, 5279.
46. Doecke, C. W.; Garrat, P. J.; Shahriari-Zavareh, H.; Zahler, R. J. Org. Chem. 1984, 49, 1412. The syntheses of the compound give extremely low yields and require many optimizations of conditions. We are currently developing a single-step process for the synthesis of this compound.