The ansa effect in permethylmolybdenocene chemistry: A [Me2Si] ansa bridge promotes intermolecular C-H and C-C bond activation

Organometallics

Volumn 18, Issue 13, 1999, Pages

  Churchill, David ^a   Shin, Jun Ho ^a   Hascall, Tony ^a   Hahn, Juliet M ^a   Bridgewater, Brian M ^a   Parkin, Gerard ^a  

^a Och Spine at New York Presbyterian Hospitals   (United States)

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EID: 3943089163     PISSN: 02767333     EISSN: None     Source Type: Journal    
DOI: None     Document Type: Article

References (51)

1. For leading reports describing differences in the chemistry of ansa and non-ansa systems, see: (a) Conway, S. L. J.; Dijkstra, T.; Doerrer, L. H.; Green, J. C.; Green, M. L. H.; Stephens, M. L. H. J. Chem. Soc., Dalton Trans. 1998, 2689-2695. (b) Labella, L.; Chernega, A.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1995, 395-402. (c) Chernega, A.; Cook, J.; Green, M. L. H.; Labella, L.; Simpson, S. J.; Souter, J.; Stephens, A. H. H. J. Chem. Soc., Dalton Trans. 1997, 3225-3243 and references therein. (d) Wochner, F.; Brintzinger, H. H. J. Organomet. Chem. 1986, 309, 65-75. (e) Smith, J. A.; Brintzinger, H. H. J. Organomet. Chem. 1981, 218, 159-167. (f) Dorer, B.; Diebold, J.; Weyand, O.; Brintzinger, H. H. J. Organomet. Chem. 1992, 427, 245-255. (g) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828-1838 and references therein.
2. For leading reports describing differences in the chemistry of ansa and non-ansa systems, see: (a) Conway, S. L. J.; Dijkstra, T.; Doerrer, L. H.; Green, J. C.; Green, M. L. H.; Stephens, M. L. H. J. Chem. Soc., Dalton Trans. 1998, 2689-2695. (b) Labella, L.; Chernega, A.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1995, 395-402. (c) Chernega, A.; Cook, J.; Green, M. L. H.; Labella, L.; Simpson, S. J.; Souter, J.; Stephens, A. H. H. J. Chem. Soc., Dalton Trans. 1997, 3225-3243 and references therein. (d) Wochner, F.; Brintzinger, H. H. J. Organomet. Chem. 1986, 309, 65-75. (e) Smith, J. A.; Brintzinger, H. H. J. Organomet. Chem. 1981, 218, 159-167. (f) Dorer, B.; Diebold, J.; Weyand, O.; Brintzinger, H. H. J. Organomet. Chem. 1992, 427, 245-255. (g) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828-1838 and references therein.
3. For leading reports describing differences in the chemistry of ansa and non-ansa systems, see: (a) Conway, S. L. J.; Dijkstra, T.; Doerrer, L. H.; Green, J. C.; Green, M. L. H.; Stephens, M. L. H. J. Chem. Soc., Dalton Trans. 1998, 2689-2695. (b) Labella, L.; Chernega, A.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1995, 395-402. (c) Chernega, A.; Cook, J.; Green, M. L. H.; Labella, L.; Simpson, S. J.; Souter, J.; Stephens, A. H. H. J. Chem. Soc., Dalton Trans. 1997, 3225-3243 and references therein. (d) Wochner, F.; Brintzinger, H. H. J. Organomet. Chem. 1986, 309, 65-75. (e) Smith, J. A.; Brintzinger, H. H. J. Organomet. Chem. 1981, 218, 159-167. (f) Dorer, B.; Diebold, J.; Weyand, O.; Brintzinger, H. H. J. Organomet. Chem. 1992, 427, 245-255. (g) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828-1838 and references therein.
4. For leading reports describing differences in the chemistry of ansa and non-ansa systems, see: (a) Conway, S. L. J.; Dijkstra, T.; Doerrer, L. H.; Green, J. C.; Green, M. L. H.; Stephens, M. L. H. J. Chem. Soc., Dalton Trans. 1998, 2689-2695. (b) Labella, L.; Chernega, A.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1995, 395-402. (c) Chernega, A.; Cook, J.; Green, M. L. H.; Labella, L.; Simpson, S. J.; Souter, J.; Stephens, A. H. H. J. Chem. Soc., Dalton Trans. 1997, 3225-3243 and references therein. (d) Wochner, F.; Brintzinger, H. H. J. Organomet. Chem. 1986, 309, 65-75. (e) Smith, J. A.; Brintzinger, H. H. J. Organomet. Chem. 1981, 218, 159-167. (f) Dorer, B.; Diebold, J.; Weyand, O.; Brintzinger, H. H. J. Organomet. Chem. 1992, 427, 245-255. (g) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828-1838 and references therein.
5. For leading reports describing differences in the chemistry of ansa and non-ansa systems, see: (a) Conway, S. L. J.; Dijkstra, T.; Doerrer, L. H.; Green, J. C.; Green, M. L. H.; Stephens, M. L. H. J. Chem. Soc., Dalton Trans. 1998, 2689-2695. (b) Labella, L.; Chernega, A.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1995, 395-402. (c) Chernega, A.; Cook, J.; Green, M. L. H.; Labella, L.; Simpson, S. J.; Souter, J.; Stephens, A. H. H. J. Chem. Soc., Dalton Trans. 1997, 3225-3243 and references therein. (d) Wochner, F.; Brintzinger, H. H. J. Organomet. Chem. 1986, 309, 65-75. (e) Smith, J. A.; Brintzinger, H. H. J. Organomet. Chem. 1981, 218, 159-167. (f) Dorer, B.; Diebold, J.; Weyand, O.; Brintzinger, H. H. J. Organomet. Chem. 1992, 427, 245-255. (g) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828-1838 and references therein.
6. For leading reports describing differences in the chemistry of ansa and non-ansa systems, see: (a) Conway, S. L. J.; Dijkstra, T.; Doerrer, L. H.; Green, J. C.; Green, M. L. H.; Stephens, M. L. H. J. Chem. Soc., Dalton Trans. 1998, 2689-2695. (b) Labella, L.; Chernega, A.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1995, 395-402. (c) Chernega, A.; Cook, J.; Green, M. L. H.; Labella, L.; Simpson, S. J.; Souter, J.; Stephens, A. H. H. J. Chem. Soc., Dalton Trans. 1997, 3225-3243 and references therein. (d) Wochner, F.; Brintzinger, H. H. J. Organomet. Chem. 1986, 309, 65-75. (e) Smith, J. A.; Brintzinger, H. H. J. Organomet. Chem. 1981, 218, 159-167. (f) Dorer, B.; Diebold, J.; Weyand, O.; Brintzinger, H. H. J. Organomet. Chem. 1992, 427, 245-255. (g) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828-1838 and references therein.
7. For leading reports describing differences in the chemistry of ansa and non-ansa systems, see: (a) Conway, S. L. J.; Dijkstra, T.; Doerrer, L. H.; Green, J. C.; Green, M. L. H.; Stephens, M. L. H. J. Chem. Soc., Dalton Trans. 1998, 2689-2695. (b) Labella, L.; Chernega, A.; Green, M. L. H. J. Chem. Soc., Dalton Trans. 1995, 395-402. (c) Chernega, A.; Cook, J.; Green, M. L. H.; Labella, L.; Simpson, S. J.; Souter, J.; Stephens, A. H. H. J. Chem. Soc., Dalton Trans. 1997, 3225-3243 and references therein. (d) Wochner, F.; Brintzinger, H. H. J. Organomet. Chem. 1986, 309, 65-75. (e) Smith, J. A.; Brintzinger, H. H. J. Organomet. Chem. 1981, 218, 159-167. (f) Dorer, B.; Diebold, J.; Weyand, O.; Brintzinger, H. H. J. Organomet. Chem. 1992, 427, 245-255. (g) Fendrick, C. M.; Schertz, L. D.; Day, V. W.; Marks, T. J. Organometallics 1988, 7, 1828-1838 and references therein.
8. Our reason for studying permethylated ansa-metallocenes is associated with the fact that such substitution frequently allows isolation of complexes that have no counterparts in the corresponding unsubstituted cyclopentadienyl system. For reviews of heavily substituted cyclopentadienyl ligands, see: (a) Janiak, C.; Schumann, H. Adv. Organomet. Chem. 1991, 33, 291-393. (b) Okuda, J. Top. Curr. Chem. 1991, 160, 97-145.
9. Our reason for studying permethylated ansa-metallocenes is associated with the fact that such substitution frequently allows isolation of complexes that have no counterparts in the corresponding unsubstituted cyclopentadienyl system. For reviews of heavily substituted cyclopentadienyl ligands, see: (a) Janiak, C.; Schumann, H. Adv. Organomet. Chem. 1991, 33, 291-393. (b) Okuda, J. Top. Curr. Chem. 1991, 160, 97-145.
10. Lee, H.; Desrosiers, P. J.; Guzei, I.; Rheingold, A. L.; Parkin, G. J. Am. Chem. Soc. 1998, 120, 3255-3256.
11. 2.
12. tCP) have been determined by X-ray diffraction. See the Supporting Information.
13. 2 is prepared by a modification of the literature method. See: Thomas, J. L. J. Am. Chem. Soc. 1973, 95, 1838-1848.
14. 2 in cyclohexane has been previously described. See: Cloke, F. G. N.; Day, J. P.; Green, J. C.; Morley, C. P.; Swaim, A. C. J. Chem. Soc., Dalton Trans. 1991, 789-796.
15. 2, and has only been spectroscopically characterized.
16. 2-Mo].
17. 2)-MoH.
18. For a discussion of the factors which influence the interconversion of olefin and vinyl-hydride complexes, see: (a) Jiménez-Cataño, R.; Niu, S.; Hall, M. B. Organometallics 1997, 16, 1962-1968 and references therein. (b) Siegbahn, P. E. M.; Blomberg, M. R. A.; Svensson, M. J. Am. Chem. Soc. 1993, 115, 1952-1958.
19. For a discussion of the factors which influence the interconversion of olefin and vinyl-hydride complexes, see: (a) Jiménez-Cataño, R.; Niu, S.; Hall, M. B. Organometallics 1997, 16, 1962-1968 and references therein. (b) Siegbahn, P. E. M.; Blomberg, M. R. A.; Svensson, M. J. Am. Chem. Soc. 1993, 115, 1952-1958.
20. 1H NMR spectroscopy.
21. 2CN)H by C-H bond activation. While we agree that it is possible for the initial interaction not to involve C-C bond cleavage, so that the activation step may be intramolecular, we nevertheless feel that it is appropriate to describe the overall reaction as intermolecular.
22. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
23. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
24. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
25. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
26. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
27. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
28. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
29. For examples of C-C bond activation reactions, see: (a) Wick, D. D.; Northcutt, T. O.; Lachicotte, R. J.; Jones, W. D. Organometallics 1998, 17, 4484-4492. (b) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J. Am. Chem. Soc. 1996, 118, 12406-12415. (c) Liou, S.-Y.; Van der Boom, M. E.; Milstein, D. J. Chem. Soc., Chem. Commun. 1998, 687-688. (d) Gozin, M.; Weisman, A.; Ben-David, Y.; Milstein, D. Nature 1993, 364, 699-701. (e) Suggs, J. W.; Jun, C.-H. J. Am. Chem. Soc. 1986, 108, 4679-4681. (f) Suggs, J. W.; Jun, C.-H. J. Chem. Soc., Chem. Commun. 1985, 92-93. (g) Crabtree, R. H.; Dion, R. P.; Gibboni, D. J.; McGrath, D. V.; Holt, E. M. 1986, 108, 7222-7227. (h) Suzuki, H.; Takaya, Y.; Takemori, T.; Tanaka, M. J. Am. Chem. Soc. 1994, 116, 10779-10780.
30. +, respectively: (a) Ittel, S. D.; Tolman, C. A.; English, A. D.; Jesson, J. P. J. Am. Chem. Soc. 1978, 100, 7577-7585. (b) English, A. D.; Herskovitz, T. J. Am. Chem. Soc. 1977, 99, 1648-1649.
31. +, respectively: (a) Ittel, S. D.; Tolman, C. A.; English, A. D.; Jesson, J. P. J. Am. Chem. Soc. 1978, 100, 7577-7585. (b) English, A. D.; Herskovitz, T. J. Am. Chem. Soc. 1977, 99, 1648-1649.
32. 2 (Ln = La, Ce). See: Heeres, H. J.; Meetsma, A.; Teuben, J. H. Angew. Chem., Int. Ed. Engl. 1990, 29, 420-422.
33. 2Ni(R)CN, but the products were unstable and could not be isolated. See: (a) Morvillo, A.; Turco, A. J. Organomet. Chem. 1981, 208, 103-113. (b) Favero, G.; Morvillo, A.; Turco, A. Gazz. Chim. Ital. 1979, 109, 27-28.
34. 2Ni(R)CN, but the products were unstable and could not be isolated. See: (a) Morvillo, A.; Turco, A. J. Organomet. Chem. 1981, 208, 103-113. (b) Favero, G.; Morvillo, A.; Turco, A. Gazz. Chim. Ital. 1979, 109, 27-28.
35. 18c (a) Gerlach, D. H.; Kane, A. R.; Parshall, G. W.; Jesson, J. P.; Muetterties, E. L. J. Am. Chem. Soc. 1971, 93, 3543-3544. (b) Parshall, G. W. J. Am. Chem. Soc. 1974, 96, 2360-2366. (c) Burmeister, J. L.; Edwards, L. M. J. Chem. Soc. A 1971, 1663-1666.
36. 18c (a) Gerlach, D. H.; Kane, A. R.; Parshall, G. W.; Jesson, J. P.; Muetterties, E. L. J. Am. Chem. Soc. 1971, 93, 3543-3544. (b) Parshall, G. W. J. Am. Chem. Soc. 1974, 96, 2360-2366. (c) Burmeister, J. L.; Edwards, L. M. J. Chem. Soc. A 1971, 1663-1666.
37. 18c (a) Gerlach, D. H.; Kane, A. R.; Parshall, G. W.; Jesson, J. P.; Muetterties, E. L. J. Am. Chem. Soc. 1971, 93, 3543-3544. (b) Parshall, G. W. J. Am. Chem. Soc. 1974, 96, 2360-2366. (c) Burmeister, J. L.; Edwards, L. M. J. Chem. Soc. A 1971, 1663-1666.
38. 3UR. See: Adam, R.; Villiers, C.; Ephritikhine, M.; Lance, M.; Nierlich, M.; Vigner, J. J. Organomet. Chem. 1983, 445, 99-106.
39. For a review of the chemistry of coordinated RCN complexes, see: Michelin, R. A.; Mozzon, M.; Bertani, R. Coord. Chem. Rev. 1996, 147, 299-338.
40. (a) Wright, T. C.; Wilkinson, G.; Motevalli, M.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1986, 2017-2019.
41. (b) Bullock, R. M.; Headford, C. B. L.; Hennessy, K. M.; Kegley, S. E.; Norton, J. R. J. Am. Chem. Soc. 1989, 111, 3897-3908.
42. For recent reviews on phosphaalkyne complexes, see: (a) Nixon, J. F. Chem. Soc. Rev. 1995, 319-328. (b) Nixon, J. F. Coord. Chem. Rev. 1995, 145, 201-258.
43. For recent reviews on phosphaalkyne complexes, see: (a) Nixon, J. F. Chem. Soc. Rev. 1995, 319-328. (b) Nixon, J. F. Coord. Chem. Rev. 1995, 145, 201-258.
44. tCP was kindly provided by Professor F. G. N. Cloke.
45. 4 does not occur thermally but is observed to occur photochemically (Scheme 2).
46. 6.
47. 6.
48. -1 and ΔS‡ = -2(1) eu.
49. Green, J. C.; Jardine, C. N. J. Chem. Soc., Dalton Trans. 1998, 1057-1061.
50. Shin, J. H.; Parkin, G. Unpublished results.
51. -1) show a similar trend. See: Schaper, F.; Rentzsch, M.; Prosenc, M.-H.; Rief, U.; Schmidt, K.; Brintzinger, H. H. J. Organomet. Chem. 1997, 534, 67-79.