Valence bond diagrams and chemical reactivity

Angewandte Chemie - International Edition

Volumn 38, Issue 5, 1999, Pages 586-625

  Shaik, Sason ^a   Shurki, Avital ^a  

^a HEBREW UNIVERSITY OF JERUSALEM   (Israel)

Author keywords

Avoided crossing; Reaction mechanisms; Selection rules; Transition states; Valence bond diagrams

Indexed keywords

ALKYL GROUP; ORGANOMETALLIC COMPOUND;

CATALYSIS; CHEMICAL BOND; CHEMICAL REACTION; COVALENT BOND; ELECTRON TRANSPORT; ENERGY TRANSFER; HYDROGEN BOND; IONIZATION; ISOMERISM; OXIDATION REDUCTION REACTION; PROTON TRANSPORT; REACTION ANALYSIS; REVIEW; STEREOCHEMISTRY; STRUCTURE ACTIVITY RELATION;

EID: 0033104833     PISSN: 14337851     EISSN: None     Source Type: Journal    
DOI: 10.1002/(SICI)1521-3773(19990301)38:5<586::AID-ANIE586>3.0.CO;2-T     Document Type: Review

References (234)

1. S. S. Shaik, J. Am. Chem. Soc. 1981, 103, 3692.
2. R. B. Woodward, R. Hoffmann, Angew. Chem. 1969, 81, 797;
3. Angew. Chem. Int. Ed. Engl. 1969, 8, 781.
4. For example, a) M. G. Evans, M. Polanyi, Trans. Faraday Soc. 1938, 34, 11;
5. b) A. Warshel, R. M. Weiss, J. Am. Chem. Soc. 1980, 102, 6218;
6. c) W. T. A. M. van der Lugt, L. J. Osterhoff, J. Am. Chem. Soc. 1969, 91, 6042;
7. d) J. Michl, Top. Curr. Chem. 1974, 46, 1;
8. e) "Unified Valence Bond Theory of Electronic Structure. Applications": N. D. Epiotis, Lect. Notes Chem. 1983, 34, 1;
9. f) L. Salem, Science 1976, 191, 822.
10. a) S. S. Shaik, Prog. Phys. Org. Chem. 1985, 15, 197;
11. b) S. S. Shaik, H. B. Schlegel, S. Wolfe, Theoretical Aspects of Physical Organic Chemistry, Wiley-Interscience, New York, 1992;
12. c) S. S. Shaik, Acta Chem. Scand. 1990, 44, 205;
13. d) S. S. Shaik, P. C. Hiberty in Theoretical Models for Chemical Bonding, Vol. 4 (Ed.: Z. B. Maksic), Springer, Heidelberg, 1991, p. 269;
14. e) A. Pross, S. S. Shaik, Acc. Chem. Res. 1983, 16, 363;
15. f) A. Pross, Adv. Phys. Org. Chem. 1985, 21, 99;
16. g) A. Pross, Theoretical and Physical Principles of Organic Reactivity, Wiley-Interscience, New York, 1995;
17. h) A. Pross, Acc. Chem. Res. 1985, 18, 212;
18. i) A. Pross, D. M. Chipman, Free Radicals Biol. Med. 1987, 3, 55.
19. a) P. Maitre, P. C. Hiberty, G. Ohanessian, S. S. Shaik, J. Phys. Chem. 1990, 94, 4089;
20. b) G. Sini, S. Shaik, P. C. Hiberty, J. Chem. Soc. Perkin Trans. 2 1992, 1019;
21. c) G. Sini, S. S. Shaik, J.-M. Lefour, G. Ohanessian, P. C. Hiberty, J. Phys. Chem. 1989, 93, 5661,
22. d) G. Sini, G. Ohanessian, P. C. Hiberty, S. S. Shaik, J. Am. Chem. Soc. 1990, 112, 1407;
23. G. Sini, P. C. Hiberty, S. S. Shaik, J. Chem. Soc. Chem. Commun. 1989, 772,
24. e) P. Maitre, F. Volatron, P. C. Hiberty, S. S. Shaik, Inorg. Chem. 1990, 29, 3047;
25. f) P. R. Benneyworth, G. G. Balint-Kurti, M. J. Davis, I. H. Williams, J. Phys. Chem. 1992, 96, 4346.
26. For recent methods of good accuracy, see for example a) P. C. Hiberty, J. P. Flament, E. Noizet, Chem. Phys. Lett. 1992, 189, 259;
27. P. C. Hiberty, S. Humbel, C. P. Byrman, J. H. van Lenthe, J. Chem. Phys. 1994, 101, 5969;
28. b) W. A. Goddard III, L. B. Harding, Annu. Rev. Phys. Chem. 1978, 29, 363;
29. A. F. Voter, W. A. Goddard III, J. Chem. Phys. 1981, 75, 3638;
30. c) J. Verbeek, J. H. Langenberg, C. P. Byrman, J. H. van Lenthe, TURTLE - an Ab Initio VB/VBSCF/VBCI Program, Theoretical Chemistry Group, Debye Institute, University of Utrecht, 1993;
31. J. Verbeek, J. H. van Lenthe, Int. J. Quantum Chem. 1991, XL, 201;
32. d) D. L. Cooper, J. Gerratt, M. Raimondi, Adv. Chem. Phys. 1987, 69, 319;
33. D. L. Cooper, J. Gerratt, M. Raimondi, Chem. Rev. 1991, 91, 929;
34. e) Y. Mo, Q. Zhang, J. Phys. Chem. 1995, 99, 8535;
35. Y. Mo, Z. Lin, W. Wu, Q. Zhang, J. Phys. Chem. 1996, 100, 6469;
36. f) W. Wu, R. McWeeny, J. Chem. Phys. 1994, 101, 4826.
37. a) S. S. Shaik in New Theoretical Concepts for Understanding Organic Reactions, Vol. C267 (Eds.: J. Bertrán, I. G. Csizmadia), Kluwer, Dordrecht, 1989, p. 165;
38. b) S. Shaik, J. Mol. Liq. 1994, 61, 49;
39. c) S. Shaik, P. C. Hiberty, Adv. Quantum Chem. 1995, 26, 99.
40. D. Schröder, H. Schwarz, Angew. Chem. 1995, 107, 2126;
41. Angew. Chem. Int. Ed. Engl. 1995, 34, 1973.
42. H. Zipse, Angew. Chem. 1994, 106, 2019;
43. Angew. Chem. Int. Ed. Engl. 1994, 33, 1985;
44. b) H. Zipse, J. Am. Chem. Soc. 1994, 116, 10773.
45. S. S. Shaik, E. Duzy, A. Bartuv, J. Phys. Chem. 1990, 94, 6574.
46. R. McWeeny, Methods of Molecular Quantum Mechanics, 2nd ed., Academic Press, London, 1992, chapters 4 and 7.
47. W. Heitler, F. London, Z. Phys. 1927, 44, 455.
48. S. Shaik, P. Maitre, G. Sini, P. C. Hiberty, J. Am. Chem. Soc. 1992, 114, 7861.
49. a) D. Lauvergnat, P. C. Hiberty, D. Danovich, S. Shaij, J. Phys. Chem. 1996, 100, 5715;
50. b) G. Sini, P. Maitre, P. C. Hiberty, S. S. Shaik, J. Mol. Struct. (THEOCHEM) 1991, 229, 163;
51. c) H. Basch, P. Aped, S. Hoz, Mol. Phys. 1996, 89, 331.
52. T. F. O'Malley, Adv. Atom. Mol. Phys. 1971, 7, 223.
53. R. A. Ogg, Jr., M. Polanyi, Trans. Faraday Soc. 1935, 31, 604.
54. S. S. Shaik, J. Org. Chem. 1987, 52, 1563.
55. H. J. Kim, J. T. Hynes, J. Am. Chem. Soc. 1992, 114, 10 508, 10 528.
56. a) P. Delahay, Acc. Chem. Res. 1982, 15, 40;
57. b) M. J. Blandamer, M. F. Fox, Chem. Rev. 1970, 70, 59.
58. S. S. Shaik, J. Am. Chem. Soc. 1984, 106, 1227.
59. C. D. Ritchie, J. Am. Chem. Soc. 1983, 105, 7313.
60. H. Mayr, M. Patz, Angew. Chem. 1994, 106, 990;
61. Angew. Chem. Int. Ed. Engl. 1994, 33, 938.
62. a) H. Feinberg, H. M. Greenblatt, G. Shoham, J. Chem. Inf. Comput. Sci. 1993, 33, 501;
63. b) H. Feinberg, H. M. Greenblatt, V. Behar, C. Gilon, S. Cohen, A. Bino, G. Shoham, Acta Crystallogr. Sect. D 1995, 51, 428.
64. a) A. Warshel, Acc. Chem. Res. 1981, 14, 284;
65. b) A. Warshel, Proc. Natl. Acad. Sci. USA 1978, 75, 5250.
66. a) J. M. Tedder, J. C. Walton, Adv. Phys. Org. Chem. 1978, 16, 51;
67. b) B. Giese, X. Beyrich-Graf, J. Burger, C. Kesselheim, M. Senn, T. Schäfer, Angew. Chem. 1993, 105, 1850;
68. Angew. Chem. Int. Ed. Engl. 1993, 32, 1742.
69. Z. Rappoport, Acc. Chem. Res. 1981, 14, 7.
70. A. Sevin, P. C. Hiberty, J.-M. Lefour, J. Am. Chem. Soc. 1987, 109, 1845.
71. a) H. H. Cornehl, G. Hornung, H. Schwarz, J. Am. Chem. Soc. 1996, 118, 9960;
72. b) J. N. Harvey, D. Schröder, W. Koch, D. Danovich, S. Shaik, H. Schwarz, Chem. Phys. Lett. 1997, 278, 391.
73. R. Hoffmann, Angew. Chem. 1982, 94, 725;
74. Angew. Chem. Int. Ed. Engl. 1982, 21, 711.
75. H. Yamataka, S. Nagase, J. Org. Chem. 1988, 53, 3232.
76. a) A. Pross, H. Yamataka, S. Nagase, J. Phys. Org. Chem. 1991, 4, 135;
77. b) M. W. Wong, A. Pross, L. Radom, Isr. J. Chem. 1993, 33, 415.
78. D. J. Bellville, D. D. Wirth, N. L. Bauld, J. Am. Chem. Soc. 1981, 103, 718;
79. D. J. Bellville, N. L. Bauld, J. Am. Chem. Soc. 1982, 104, 2665;
80. R. A. Pabon, D. J. Bellville, N. L. Bauld, J. Am. Chem. Soc. 1983, 105, 5158.
81. F. Bernardi, A. Bottoni, M. Olivucci, A. Venturini, M. A. Robb, J. Chem. Soc. Faraday Trans. 1994, 90, 1617.
82. P. Jungwirth, T. Bally, J. Am. Chem. Soc. 1993, 115, 5783.
83. The fairly small localization energy of the cation is neglected for simplicity; see also F. M. Bickelhaupt, R. Hoffmann, R. D. Levine, J. Phys. Chem. A 1997, 101, 8255.
84. a) T. P. Begley, Acc. Chem. Res. 1994, 27, 394;
85. b) H.-W. Park, S.-T. Kim, A. Sancar, J. Deisenhofer, Science 1995, 268, 1866.
86. A. Ioffe, S. Shaik, J. Chem. Soc. Perkin Trans. 2 1992, 2101.
87. a) E. T. Seidl, R. S. Grev, H. F. Schaefer III, J. Am. Chem. Soc. 1992, 114, 3643;
88. b) F. Bernardi, A. Bottoni, M. Olivucci, M. A. Robb, A. Venturini, J. Am. Chem. Soc. 1993, 115, 3322.
89. a) R. West, Angew. Chem. 1987, 99, 1231;
90. Angew. Chem. Int. Ed. Engl. 1987, 26, 1201;
91. b) Y. Apeloig in The Chemistry of Organic Silicon Compounds (Eds.: S. Patai, Z. Rappoport), Wiley, Chichester, 1989, chapter 2.
92. S. Shaik, A. Ioffe, unpublished results.
93. S. S. Shaik, P. C. Hiberty, G. Ohanessian, J.-M. Lefour, J. Phys. Chem. 1988, 92, 5086.
94. M. J. S. Dewar, J. Am. Chem. Soc. 1984, 106, 209.
95. D. L. King, D. R. Herschbach, Faraday Discuss. Chem. Soc. 1973, 55, 331.
96. a) G. K. Cook, J. M. Mayer, J. Am. Chem. Soc. 1994, 116, 1855;
97. b) G. K. Cook, J. M. Mayer, J. Am. Chem. Soc. 1995, 117, 7139;
98. c) K. A. Gardner, J. M. Mayer, Science 1995, 269, 1849.
99. A. K. Rappé, W. A. Goddard III, J. Am. Chem. Soc. 1982, 104, 3287.
100. a) A. Fiedler, D. Schröder, S. Shaik, H. Schwarz, J. Am. Chem. Soc. 1994, 116, 10 734;
101. b) M. F. Ryan, A. Fiedler, D. Schröder, H. Schwarz, J. Am. Chem. Soc. 1995, 117, 2033;
102. c) Y.-M. Chen, D. E. Clemmer, P. B. Armentrout, J. Am. Chem. Soc. 1994, 116, 7815;
103. d) D. E. Clemmer, Y.-M. Chen, F. A. Khan, P. B. Armentrout, J. Phys. Chem. 1994, 98, 6522;
104. e) S. Shaik, D. Danovich, A. Fiedler, D. Schröder, H. Schwarz, Helv. Chim. Acta 1995, 78, 1393,
105. f) S. Shaik, M. Filatov, J. Phys. Chem. A 1998, 102, 3835.
106. a) C. L. Lasko, R. M. Miller, D. S. Tinti, Chem. Phys. Lett. 1986, 130, 359;
107. b) R. M. Miller, D. S. Tinti, D. A. Case, Inorg. Chem. 1989, 28, 2738.
108. E. Buncel, S. S. Shaik, I.-H. Um, S. Wolfe, J. Am. Chem. Soc. 1988, 110, 1275.
109. I. M. Kovach, J. P. Elrod, R. L. Schowen, J. Am. Chem. Soc. 1980, 102, 7530.
110. D. G. Oakenfull, T. Riley, V. Gold, J. Chem. Soc. Chem. Commun. 1966, 385;
111. V. Gold, D. G. Oakenfull, T. Riley, J. Chem. Soc. B 1968, 515.
112. J. K. Kochi, Angew. Chem. 1988, 100, 1331;
113. Angew. Chem. Int. Ed. Engl. 1988, 27, 1227.
114. S. Fukuzumi, S. Koumitsu, K. Hironaka, T. Tanaka, J. Am. Chem. Soc. 1987, 109, 305;
115. M. Ishikawa, S. Fukuzumi, J. Chem. Soc. Faraday Trans. 1990, 86, 3531.
116. E. Baciocchi, L. Mandolini, Tetrahedron 1987, 43, 4035.
117. For a discussion of ET mechanisms of ion radicals, see: L. Eberson, S. S. Shaik, J. Am. Chem. Soc. 1990, 112, 4484. Note the different VB situation in comparison with ET between closed-shell reactants as depicted in Figure 30
118. L. Eberson, Electron Transfer Reactions in Organic Chemistry, Springer, Berlin, 1987.
119. a) J. W. Verhoeven, W. van Gerresheim, F. M. Martens, S. M. van der Kerk, Tetrahedron 1986, 42, 975;
120. b) Y. Apeloig, O. Merin-Aharoni, D. Danovich, A. Ioffe, S. Shaik, Isr. J. Chem. 1993, 33, 387.
121. M. Patz, H. Mayr, J. Maruta, S. Fukuzumi, Angew. Chem. 1995, 107, 1351;
122. Angew. Chem. Int. Ed. Engl. 1995, 34, 1225.
123. H. H. Cornehl, C. Heinemann, D. Schröder, H. Schwarz, Organometallics 1995, 14, 992.
124. M.-D. Su, Inorg. Chem. 1995, 34, 3829.
125. A. Pross, R. A. Moss, Tetrahedron Lett. 1990, 31, 4553.
126. S. Goldstein, G. Czapski, H. Cohen, D. Meyerstein, S. Shaik, J. Chem. Soc. Faraday Trans. 1993, 89, 4045.
127. S. Shaik, A. C. Reddy, A. Ioffe, J. P. Dinnocenzo, D. Danovich, J. K. Cho, J. Am. Chem. Soc. 1995, 117, 3205.
128. D. Cohen, R. Bar, S. S. Shaik, J. Am. Chem. Soc. 1986, 108, 231.
129. S. S. Shaik, P. C. Hiberty, J.-M. Lefour, G. Ohanessian, J. Am. Chem. Soc. 1987, 109, 363.
130. A. Demolliens, O. Eisenstein, P. C. Hiberty, J. M. Lefour, G. Ohanessian, S. S. Shaik, F. Volatron, J. Am. Chem. Soc. 1989, 111, 5623.
131. See the appendix to chapters in ref. [4b], pp. 128-131.
132. L. Eberson, R. González-Luque, M. Merchán, F. Radner, B. O. Roos, S. Shaik, J. Chem. Soc. Perkin Trans. 2 1997, 463.
133. av - B
134. a) S. S. Shaik, Nouv. J. Chim. 1983, 7, 201;
135. b) S. S. Shaik, J. Am. Chem. Soc. 1983, 105, 4359.
136. a) S. S. Shaik, Can. J. Chem. 1986, 64, 96;
137. b) S. S. Shaik, Isr. J. Chem. 1985, 26, 367.
138. G. Sini, Dissertation, Université de Paris-Sud, Orsay, France, 1991.
139. a) B. D. Wladkowski, J. L. Wilbur, J. I. Brauman, J. Am. Chem. Soc. 1994, 116, 2471;
140. b) B. D. Wladkowski, K. F. Lim, W. D. Allen, J. I. Brauman, J. Am. Chem. Soc. 1992, 114, 9136.
141. a) J. Hine, J. Am. Chem. Soc. 1950, 72, 2438;
142. b) J. Hine, A. M. Dowell, Jr., J. Am. Chem. Soc. 1954, 76, 2688;
143. c) J. Hine, C. H. Thomas, S. J. Ehrenson, J. Am. Chem. Soc. 1955, 77, 3886;
144. d) J. Hine, S. J. Ehrenson, W. H. Brader, Jr., J. Am. Chem. Soc. 1956, 78, 2282.
145. a) R. F. Hudson, G. Klopman, J. Chem. Soc. 1962, 1062;
146. V. P. Vitullo, J. Grabowski, S. Sridharan, J. Am. Chem. Soc. 1980, 102, 6463;
147. F. P. Ballistreri, E. Maccarone, A. Mamo, J. Org. Chem. 1976, 41, 3364;
148. b) S. D. Ross, M. Finkelstein, R. C. Petersen, J. Am. Chem. Soc. 1968, 90, 6411;
149. A. Halvorsen, J. Songstad, J. Chem. Soc. Chem. Commun. 1978, 327;
150. c) C. Eaborn, J. C. Jeffrey, J. Chem. Soc. 1954, 4266;
151. M. A. Cook, C. Eaborn, D. R. M. Walton, J. Organomet. Chem. 1971, 29, 389.
152. H. Mayr in Cationic Polymerizations (Ed.: K. Matyjaszewski), Marcel Dekker, New York, 1996, chapter 2, p. 51.
153. S. S. Shaik, E. Canadell, J. Am. Chem. Soc. 1990, 112, 1446.
154. E. Canadell, O. Eisenstein, G. Ohanessian, J. M. Poblet, J. Phys. Chem. 1985, 89, 4856.
155. S. Shaik, A. C. Reddy, J. Chem. Soc. Faraday Trans. 1994, 90, 1631.
156. M. N. Glukhovtsev, A. Pross, L. Radom, J. Am. Chem. Soc. 1995, 117, 2024. The barrier datum for X = Fis used to obtain the f value, which is carried over to all other reactions.
157. G. Ohanessian, P. C. Hiberty, J.-M. Lefour, J.-P. Flament, S. S. Shaik, Inorg. Chem. 1988, 27, 2219.
158. ab.
159. M. G. Evans, E. Warhurst, Trans. Faraday Soc. 1938, 34, 614;
160. M. G. Evans, Trans. Faraday Soc. 1939, 35, 824.
161. M. A. Robb, F. Bernardi in New Theoretical Concepts for Understanding Organic Reactions, Vol. C267 (Eds.: J. Bertrán, I. G. Csizmadia), Kluwer, Dordrecht, 1989, pp. 101;
162. F. Bernardi, M. Olivucci, M. A. Robb in New Theoretical Concepts for Understanding Organic Reactions, Vol. C267 (Eds.: J. Bertrán, I. G. Csizmadia), Kluwer, Dordrecht, 1989, p. 147.
163. a) K. N. Houk, Y. Li, J. D. Evanseck, Angew. Chem. 1992, 104, 711;
164. Angew. Chem. Int. Ed. Engl. 1992, 31, 682;
165. b) K. N. Houk, J. González, Y. Li, Acc. Chem. Res. 1995 28, 81;
166. c) B. R. Beno, S. Wisley, K. N. Houk, J. Am. Chem. Soc., in press.
167. Note that the diradical in the Zewail experiment may originate in the excited state (K. N. Houk, private communication).
168. B. A. Horn, J. L. Herek, A. H. Zewail, J. Am. Chem. Soc. 1996, 118, 8755.
169. R. S. Mulliken, J. Am. Chem. Soc. 1952, 74, 811;
170. R. S. Mulliken, J. Phys. Chem. 1952, 56, 801.
171. N. D. Epiotis, Angew. Chem. 1974, 86, 825;
172. Angew. Chem. Int. Ed. Engl. 1974, 13, 751;
173. N. D. Epiotis, Theory of Organic Reactions, Springer, Berlin, 1978.
174. S. S. Shaik, J. P. Dinnocenzo, J. Org. Chem. 1990, 55, 3434.
175. L. Eberson, M. P. Hartshorn, F. Radner, M. Merchán, B. O. Roos, Acta Chem. Scand. 1993, 47, 176;
176. L. Eberson, F. Radner, Acta Chem. Scand. 1992, 46, 312, 802.
177. J. P. Dinnocenzo, W. P. Todd, T. R. Simpson, I. R. Gould, J. Am. Chem. Soc. 1990, 112, 2462.
178. S. Shaik, A. C. Reddy, unpublished results.
179. a) G. N. Sastry, S. Shaik, J. Am. Chem. Soc. 1995, 117, 3290;
180. b) G. N. Sastry, A. C. Reddy, S. Shaik, Angew. Chem. 1995, 107, 1619;
181. Angew. Chem. Int. Ed. Engl. 1995, 34, 1495;
182. c) G. N. Sastry, S. Shaik, J. Phys. Chem. 1996, 100, 12241.
183. N. Kimura, S. Takamuku, J. Am. Chem. Soc. 1994, 116, 4087;
184. N. Kimura, S. Takamuku, Bull. Chem. Soc. Jpn. 1991, 64, 2433.
185. This system (see ref. [92c] ) was suggested by J. P. Dinnocenzo during the sojourn of one of the authors (S.S.) on a sabbatical leave in the university of Rochester.
186. This system was suggested by M. Schmittel to one of the authors (S.S.) after his talk at the International Symposium of the Volkswagenstiftung on Intra- and Intermolecular Electron Transfer in Berlin, 1996.
187. a) J. H. Incremona, C. J. Upton, J. Am. Chem. Soc. 1972, 94, 301;
188. C. J. Upton, J. H. Incremona, J. Org. Chem. 1976, 41, 523;
189. b) B. B. Jarvis, J. Org. Chem. 1970, 35, 924;
190. c) G. G. Maynes, D. E. Applequist, J. Am. Chem. Soc. 1973, 95, 856;
191. d) K. J. Shea, P. S. Skell, J. Am. Chem. Soc. 1973, 95, 6728;
192. e) M. L. Poutsma, J. Am. Chem. Soc. 1965, 87, 4293.
193. CC*), and hence makes an unequivocal prediction. Frontier MO theory predicts that the sum of these interactions determines the regioselectivity. The sum behaves undecidedly for qualitative reasoning. If one of the interactions is more important than the other, it is not easy to decide which one would that be (see ref. [90]).
194. b) M. Schmittel, C. Wöhrle, I. Bonn, Chem. Eur. J. 1996, 2, 1031.
195. S. Shaik in Encyclopedia of Computational Chemistry, Vol. 5 (Eds.: P. von R. Schleyer, N. L. Allinger, T. Clark, J. Gasteiger, P. A. Kollman, H. F. Schaefer III), Wiley, Chichester,pp. 3143-3159.
196. G. L. Fox, H. B. Schlegel, J. Phys. Chem. 1992, 96, 298.
197. a) D. Danovich, S. Shaik, J. Am. Chem. Soc. 1997, 119, 1773;
198. b) S. Shaik, M. Filatov, D. Schröder, H. Schwarz, Chem. Eur. J. 1998, 4, 193.
199. A. Warshel, A. Papazyan, P. A. Kollman, Science 1995, 269, 102;
200. W. W. Cleland, M. M. Kreevoy, Science 1995, 269, 104;
201. P. A. Frey, Science 1995, 269, 104.
202. - suggest a very small barrier.
203. Essentially similar results have been recalculated by us using the BOVB theory described in references [6a,b].
204. [71, 78]
205. a) R. J. P. Corriu, M. Henner, J. Organomet. Chem. 1974, 74, 1;
206. b) A. E. Reed, P. von R. Schleyer, J. Am. Chem. Soc. 1990, 112, 1434.
207. S. Harder, A. Streitwieser, J. T. Petty, P. von R. Schleyer, J. Am. Chem. Soc. 1995, 117, 3253.
208. a) R. Huisgen, Acc. Chem. Res. 1977, 10, 117, 199;
209. b) J. Sauer, R. Sustmann, Angew. Chem. 1980, 92, 773;
210. Angew. Chem. Int. Ed. Engl. 1980, 19, 779.
211. a) R. Sustmann, M. Rogge, U. Nüchter, H. Bandmann, Chem. Ber. 1992, 125, 1647;
212. b) R. Sustmann, M. Rogge, U. Nüchter, J. Harvey, Chem. Ber. 1992, 125, 1665;
213. c) M. Rese, M. Dern, K. Lücking, R. Sustmann, Liebigs Ann. 1995, 1139;
214. d) R. Sustmann, M. Rogge, U. Nüchter, H. Bandmann, Chem. Ber. 1992, 125, 1657;
215. e) K. Lücking, M. Rese, R. Sustmann, Liebigs Ann. 1995, 1129.
216. N2-type attack;
217. b) T. Okuyama, M. Ochiai, J. Am. Chem. Soc. 1997, 119, 4785.
218. H. Zipse, J. Chem. Soc. Perkin Trans. 2 1997, 2691.
219. H. Zipse, J. Am. Chem. Soc. 1997, 119, 1087, 2889;
220. H. Zipse, J. Chem. Soc. Perkin Trans. 2 1996, 1797.
221. B. Giese, X. Beyrich-Graf, J. Burger, C. Kesselheim, M. Senn, T. Schäfer, Angew. Chem. 1993, 105, 1850;
222. Angew. Chem. Int. Ed. Engl. 1993, 32, 1742.
223. a) G. N. Sastry, D. Danovich, S. Shaik, Angew. Chem. 1996, 108, 1208;
224. Angew. Chem. Int. Ed. Engl. 1996, 35, 1098;
225. b) S. Shaik, D. Danovich, G. N. Sastry, P. Y. Ayala, H. B. Schlegel, J. Am. Chem. Soc. 1997, 119, 9237;
226. c) G. N. Sastry, S. Shaik, J. Am. Chem. Soc. 1998, 120, 2131.
227. H. B. Schlegel, J. Chem. Soc. Faraday Trans. 1994, 90, 1569;
228. P. Valtazanos, K. Ruedenberg, Theor. Chim. Acta 1986, 69, 281.
229. A. C. Reddy, D. Danovich, A. Ioffe, S. Shaik, J. Chem. Soc. Perkin Trans. 2 1995, 1525.
230. F. Bernardi, M. Olivucci, M. Robb, Isr. J. Chem. 1993, 33, 265.
231. U. Manthe, H. Köppel, J. Chem. Phys. 1990, 93, 1669.
232. a) D. M. Cyr, G. A. Bishea, M. G. Scranton, M. A. Johnson, J. Chem. Phys. 1992, 97, 5911;
233. b) M. Lipson, A. A. Deniz, K. S. Peters, J. Am. Chem. Soc. 1996, 118, 2992;
234. c) H. Quast, K. Knoll, E.-M. Peters, K. Peters, H. G. von Schnering, Chem. Ber. 1993, 126, 1047.