One-electron oxidation of paramagnetic chromium(II) alkyl complexes with alkyl halides: synthesis and structure of five-coordinate chromium(III) complexes

Abstract

The reaction of square-planar, high-spin CrR[N(SiMe₂CH₂PPh₂)₂] (R = Me, CH₂SiMe₃) with alkyl halides (MeI, CF₃CH₂I, MeBr, PhCH₂Cl) generates one-electron oxidation products Cr(R)X[N(SiMe₂CH₂PPh₂)₂], unusual examples of five-coordinate chromium(III) complexes. Cr(Me)Br[N(SiMe₂CH₂PPh₂)₂] and Cr(CH₂SiMe₃)Cl[N(SiMe₂CH₂PPh₂)₂] have been structurally characterized. Alkylation of the latter complex with LiCH₂SiMe₃ gave a five-coordinate Cr(III) dialkyl complex Cr(CH₂SiMe₃)₂[N(SiMe₂CH₂PPh₂)₂], which was structurally characterized as well. Attempts to isolate sterically unencumbered Cr(III) dialkyl (e.g., dimethyl) complexes resulted in decomposition. Addition of an excess of PhCH₂Cl to {[(Ph₂PCH₂SiMe₂)₂N]Cr}₂(µ-Cl)₂ resulted in halide-transfer to form CrCl₂(THF)[N(SiMe₂CH₂PPh₂)₂] in low yield. Reaction of the low-spin CrCp[N(SiMe₂CH₂PPh₂)₂] complex with PhCH₂Cl, however, gave both Cr(Cp)(CH₂Ph)[N(SiMe₂CH₂PPh₂)₂] and Cr(Cp)Cl[N(SiMe₂CH₂PPh₂)₂]. The five-coordinate Cr(III) alkyl halide complexes do not polymerize ethylene at 60 °C and 1 atm; the dialkyl complex Cr(CH₂SiMe₃)₂[N(SiMe₂CH₂PPh₂)₂] does catalyze polyethylene formation but is quickly deactivated. A discussion comparing the structural distortions observed in these five-coordinate high-spin d³ Cr(III) complexes with those observed in the analogous low-spin d⁶ Ir(III) complexes is presented.

References

1. J. P. Collman, L. S. Hegedus, J. R. Norton and R. G. Finke, Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill Valley, CA, 1987.
2. R. H. Crabtree, The Organometallic Chemistry of the Transition Metals, John Wiley & Sons, New York, 1994.
3. J. K. Kochi and J. W. Powers, J. Am. Chem. Soc., 1970, 92, 137.
4. J. H. Espenson, Prog. Inorg. Chem., 1983, 30, 189.
5. J. H. Espenson, Acc. Chem. Res., 1992, 25, 222.
6. W. C. Kupferschmidt and R. B. Jordan, J. Am. Chem. Soc., 1984, 106, 991.
7. M. J. Sisley and R. B. Jordan, Inorg. Chem., 1988, 27, 1963.
8. Z. Zhang and R. B. Jordan, Inorg. Chem., 1993, 32, 5472.
9. A. Bakac, V. Butkovic, J. H. Espenson and M. Orhanovic, Inorg. Chem., 1993, 32, 5886.
10. M. C. Baird, Chem. Rev., 1988, 88, 1217.
11. D. R. Tyler, Prog. Inorg. Chem., 1988, 36, 125.
12. T. A. Huber, D. H. Macartney and M. C. Baird, Organometallics, 1993, 12, 4715.
13. T. A. Huber, D. H. Macartney and M. C. Baird, Organometallics, 1995, 14, 592.
14. C. A. Goulin, T. A. Huber, J. M. Nelson, D. H. Macartney and M. C. Baird, J. Chem. Soc., Chem. Commun., 1991, 798.
15. C. A. MacConnachie, J. M. Nelson and M. C. Baird, Organometallics, 1992, 11, 2521.
16. S. L. Scott, J. H. Espenson and Z. Zhu, J. Am. Chem. Soc., 1993, 115, 1789.
17. K.-W. Lee and T. L. Brown, J. Am. Chem. Soc., 1987, 109, 3269.
18. M. D. Fryzuk, D. B. Leznoff, S. J. Rettig and R. C. Thompson, Inorg. Chem., 1994, 33, 5528.
19. M. D. Fryzuk, D. B. Leznoff and S. J. Rettig, Organometallics, 1995, 14, 5193.
20. D. F. Evans, J. Chem. Soc., 1959, 2003.
21. S. K. Sur, J. Magn. Reson., 1989, 82, 169.
22. R. L. Carlin, Magnetochemistry, Springer-Verlag, Berlin, 1986.
23. A. R. Hermes, R. J. Morris and G. S. Girolami, Organometallics, 1988, 7, 2372.
24. G. W. A. Fowles and P. T. Greene, Chem. Commun., 1966, 784.
25. P. T. Greene, B. J. Russ and J. S. Wood, J. Chem. Soc. A, 1971, 3636.
26. E. Müller, J. Krause and K. Schmiedeknecht, J. Organomet. Chem., 1972, 44, 127.
27. M. D. Fryzuk, D. B. Leznoff and S. J. Rettig, Organometallics, 1997, 16, 5116.
28. F. A. Cotton, J. Czuchajowska, L. R. Falvello and X. Feng, Inorg. Chim. Acta, 1990, 172, 135.
29. Y. Liang, G. P. A. Yap, A. L. Rheingold and K. H. Theopold, Organometallics, 1996, 15, 5284.
30. R. D. Köhn and G. Kocoik-Köhn, Angew. Chem., Int. Ed. Engl., 1994, 33, 1877.
31. E. G. Thaler, K. Folting, J. C. Huffman and K. G. Caulton, J. Organomet. Chem., 1989, 376, 343.
32. A. R. Hermes and G. S. Girolami, Inorg. Chem., 1990, 29, 313.
33. D. S. Richeson, S.-W. Hsu, N. H. Fredd, G. v. duyne and K. H. Theopold, J. Am. Chem. Soc., 1986, 108, 8273.
34. W. A. Herrmann, W. R. Thiel and E. Herdtweck, J. Organomet. Chem., 1988, 353, 323.
35. G. Bhandari, Y. Kim, J. M. McFarland, A. L. Rheingold and K. H. Theopold, Organometallics, 1995, 14, 738.
36. A. R. H. Al-Soudani, A. S. Batsanov, P. G. Edwards and J. A. K. Howard, J. Chem. Soc., Dalton Trans., 1994, 987.
37. J. C. Fettinger, S. P. Mattamana, R. Poli and R. D. Rogers, Organometallics, 1996, 15, 4211.
38. K. H. Theopold, Acc. Chem. Res., 1990, 23, 263.
39. T. G. Gardner and G. S. Girolami, J. Chem. Soc., Chem. Commun., 1987, 1758.
40. D. C. Bradley, M. B. Hursthouse and C. W. Newing, Chem. Commun., 1971, 411.
41. S. E. Nefedov, A. A. Pasynskii, I. L. Eremenko, B. Orazsakhatov, O. G. Ellert, V. M. Novotortsev, S. B. Katser, A. S. Antsyshkina and M. A. Porai-Koshits, J. Organomet. Chem., 1988, 345, 97.
42. J. N. Lisgarten, R. A. Palmer, A. M. Hemmings and D. M. Gazi, Acta Crystallogr., Sect. C, 1990, 46, 396.
43. D. M. Halepoto, L. F. Larkworthy, D. C. Povey, R. A. Siddiqui and G. W. Smith, Inorg. Chim. Acta, 1994, 227, 167.
44. D. B. Morse, T. B. Rauchfuss and S. R. Wilson, J. Am. Chem. Soc., 1988, 110, 8234.
45. G. Bhandari, A. L. Rheingold and K. H. Theopold, Chem. Eur. J., 1995, 1, 199.
46. R. D. Köhn, G. Kociok-Köhn and M. Haufe, J. Organomet. Chem., 1995, 501, 303.
47. A. Grohmann, F. H. Köhler, G. Müller and H. Zeh, Chem. Ber., 1989, 122, 897.
48. J. Krausse and G. Marx, J. Organomet. Chem., 1974, 65, 215.
49. P. W. Jolly, Acc. Chem. Res., 1996, 29, 544.
50. R. Poli, Chem. Rev., 1996, 96, 2135.
51. R. P. A. Sneeden, Organochromium Compounds, Academic Press, New York, London, 1975.
52. B. J. Thomas, S. K. Noh, G. K. Schulte, S. C. Sendlinger and K. H. Theopold, J. Am. Chem. Soc., 1991, 113, 893.
53. K. H. Theopold, R. A. Heintz, S. K. Noh and B. J. Thomas, in Homogeneous Chromium Catalysts for Olefin Polymerization, ed. W. R. Moser and D. W. Slocum, American Chemical Society, Washington, DC, 1992.
54. M. D. Fryzuk, Can. J. Chem., 1992, 70, 2839.
55. M. D. Fryzuk, P. A. MacNeil and S. J. Rettig, J. Am. Chem. Soc., 1985, 107, 6708.
56. M. D. Fryzuk, P. A. MacNeil and R. G. Ball, J. Am. Chem. Soc., 1986, 108, 6414.
57. M. D. Fryzuk, P. A. MacNeil and S. J. Rettig, Organometallics, 1986, 5, 2469.
58. M. D. Fryzuk, P. A. MacNeil, R. L. Massey and R. G. Ball, J. Organomet. Chem., 1989, 368, 231.
59. D. L. Thorn and R. Hoffmann, New J. Chem., 1979, 3, 39.
60. Y. Jean and O. Eisenstein, Polyhedron, 1988, 7, 405.
61. I. E.-I. Rachidi, O. Eisenstein and Y. Jean, New J. Chem., 1990, 14, 671.
62. J. F. Riehl, Y. Jean, O. Eisenstein and M. Pelissier, Organometallics, 1992, 11, 729.
63. R. D. Shannon and C. T. Prewit, Acta Crystallogr., Sect. B, 1969, 25, 925.
64. R. D. Shannon, Acta Crystallogr., Sect. B, 1976, 32, 751.
65. M. D. Fryzuk, P. A. MacNeil, S. J. Rettig, A. S. Secco and J. Trotter, Organometallics, 1982, 1, 918.
66. M. Schlosser and V. Ladenberger, J. Organomet. Chem., 1967, 8, 193.
67. M. D. Fryzuk, G. Giesbrecht and S. J. Rettig, Organometallics, 1996, 15, 3329.
68. G. M. Sheldrick, SADABS, University of Göttingen, 1997.
69. C. K. Johnson, ORTEP, report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976.