Iron(II) complexes with novel pentadentate ligands via C–C bond formation between various nitriles and [2,4-bis(2-pyridylmethylimino)pentane]iron(II) perchlorate: synthesis and structures ‡

Abstract

The iron(II) complex of 2,4-bis(2-pyridylmethylimino)pentane (L¹), trans-[FeL¹(MeCN)₂][ClO₄]₂·MeCN, was prepared by a template reaction and isolated as pale red crystals. An acetonitrile solution of the complex exhibited a crossover from a low- to a high-spin form above 20 °C. With this complex as precursor, a series of iron(II) complexes with novel pentadentate ligands, 3-(1-alkyl (or aryl)-methyl)-1-imino-2,4-bis(2-pyridylmethylimine) (L²), was prepared using various nitriles such as propionitrile, isobutyronitrile, benzyl cyanide, benzonitrile, 4-fluoro-, 3,4-difluoro-, and pentafluoro-benzonitrile, as well as acetonitrile, as solvents. On formation of L², the co-ordination mode of the L¹ part of the parent compound was converted from trans into cis-β with concomitant C–C bond formation between the central carbon atom of L¹ and the carbon atom of the various nitriles. The isolated triimine part in the pentadentate ligands occupies one of the trigonal faces of the distorted octahedron. The resulting complex undergoes rapid intramolecular isomerization at or above room temperature. The crystal structures of the precursor and of three new iron(II) complexes with pentadentate ligands have been determined.

References

1. M. J. Blandamer, J. Burgess, R. I. Haines, F. M. Mekhail and P. Askalani, J. Chem. Soc., Dalton Trans., 1978, 1001.
2. A. Earnshaw, E. A. King and L. F. Larkworthy, J. Chem. Soc. A, 1968, 1048.
3. V. L. Goedken, J. Chem. Soc., Chem. Commun., 1972, 207; A. M. C. Ferreira and H. E. Toma, J. Chem. Soc., Dalton Trans., 1983, 2051; M. Goto, M. Takeshita, N. Kanda, T. Sakai and V. L. Goedken, Inorg. Chem., 1985, 24, 582; M. Goto, N. Koga, Y. Ohse, H. Kurosaki, T. Komatsu and Y. Kuroda, J. Chem. Soc., Chem. Commun., 1994, 2015.
4. V. L. Goedken and D. H. Busch, J. Am. Chem. Soc., 1972, 94, 7355; K. Pohl, K. Wieghardt, W. Kaim and S. Steenken, Inorg. Chem., 1988, 27, 440.
5. S. M. Nelson and J. Rodgers, J. Chem. Soc. A, 1968, 272; R. Butcher and A. W. Addison, Inorg. Chim. Acta, 1989, 158, 211.
6. Yu-Min Chiou and Lawrence Que, jun., J. Am. Chem. Soc., 1995, 117, 3999.
7. Yan Zang, J. Kim, Yanhong Dong, E. C. Wilkinson, E. H. Appelman and Laurence Que, jun., J. Am. Chem. Soc., 1997, 119, 4197.
8. H. Toftlund and S. Yde-Andersen, Acta Chem. Scand., Ser. A, 1981, 35, 575; J. K. McCusker, K. N. Walda, R. C. Dunn, J. D. Simon, D. Magde and D. N. Hendrickson, J. Am. Chem. Soc., 1993, 115, 298; J. K. McCusker, H. Toftlund, A. L. Rheingold and D. N. Hendrickson, J. Am. Chem. Soc., 1993, 115, 1797.
9. Hsiu-Rong Chang, J. K. McCusker, H. Toftlund, S. R. Wilson, A. X. Trautwein, H. Winkler and D. N. Hendrickson, J. Am. Chem. Soc., 1990, 112, 6814.
10. D. A. Buckingham, B. M. Foxman, A. M. Sargeson and A. Zanella, J. Am. Chem. Soc., 1972, 94, 1007; D. A. Buckingham, F. R. Keene and A. M. Sargeson, J. Am. Chem. Soc., 1973, 95, 5649; K. B. Nolan and R. W. Hay, J. Chem. Soc., Dalton Trans., 1974, 914; A. W. Zanella and P. C. Ford, Inorg. Chem., 1975, 14, 42; D. A. Buckingham, P. Morris, A. M. Sargeson and A. Zanella, Inorg. Chem., 1977, 16, 1910; W. R. Ellis and W. L. Purcell, Inorg. Chem., 1982, 21, 834; D. A. Buckingham, C. R. Clark, B. M. Foxman, G. J. Gainsford, A. M. Sargeson, M. Wein and A. Zanella, Inorg. Chem., 1982, 21, 1986; N. J. Curtis and A. M. Sargeson, J. Am. Chem. Soc., 1984, 106, 625; F. Scavo and P. Helquist, Tetrahedron Lett., 1985, 26, 2603; P. Paul and K. Nag, Inorg. Chem., 1987, 26, 2969; L. Roecker, A. M. Sargeson and A. C. Willis, J. Chem. Soc., Chem. Commun., 1988, 119; W. Schulz, H. Pracejus and G. Oehme, Tetrahedron Lett., 1989, 30, 1229; A. Syamala and A. Chakravarty, Inorg. Chem., 1991, 30, 4699; J. Grigg, D. Collison, C. D. Garner, M. Helliwell, P. A. Tasker and J. M. Thorpe, J. Chem. Soc., Chem. Commun., 1993, 1807.
11. K. Bowman, D. P. Riley, D. H. Busch and P. W. R. Corfield, J. Am. Chem. Soc., 1975, 97, 5036; D. P. Riley and D. H. Busch, Inorg. Chem., 1983, 22, 4141; D. P. Riley, J. A. Stone and D. H. Busch, J. Am. Chem. Soc., 1977, 99, 767; D. P. Riley and D. H. Busch, Inorg. Chem., 1983, 22, 4141.
12. D. P. Riley, J. A. Stone and D. H. Busch, J. Am. Chem. Soc., 1976, 98, 1752.
13. K. B. Mertes, P. W. R. Corfield and D. H. Busch, Inorg. Chem., 1977, 16, 3226.
14. W. C. Weiss and V. L. Goedken, J. Am. Chem. Soc., 1976, 98, 1752; M. C. Weiss, G. C. Gordon and V. L. Goedken, J. Am. Chem. Soc., 1979, 101, 857.
15. F. Mizukami, K. Satoh, S. Niwa, T. Tsuchiya, K. Shimizu and J. Imamura, Sekiyu Gakkai Shi, 1985, 28, 293.
16. M. Goto, Y. Ishikawa, T. Ishihara, C. Nakatake, T. Higuchi, H. Kurosaki and V. L. Goedken, Chem. Commun., 1997, 539.
17. TEXSAN program system, Molecular Structure Corporation, Houston, TX, 1985 and 1992.
18. A. Bax and S. Subramanian, J. Magn. Reson., 1986, 67, 565.
19. A. Bax and M. F. Summers, J. Am. Chem. Soc., 1986, 108, 2093.
20. D. F. Evans, J. Chem. Soc., 1959, 2003.
21. O. Kahn, Molecular Magnetism, VCH, Weinheim, 1993, p. 4.
22. S. O. Wandiga, J. E. Sarneski and F. L. Urbach, Inorg. Chem., 1972, 11, 1349.
23. L. L. Martin, K. S. Hagen, A. Hauser, R. L. Martin and A. M. Sargeson, J. Chem. Soc., Chem. Commun., 1989, 2003.
24. A. Bax, R. H. Griffey and B. L. Hawkins, J. Magn. Reson., 1983, 55, 301; G. Otting and K. Wuthrich, J. Magn. Reson., 1988, 76, 569; A. Bax and D. Marion, J. Magn. Reson., 1988, 78, 186.
25. J. C. Dabrowiak and D. H. Busch, Inorg. Chem., 1975, 14, 1881.
26. R. J. H. Clark, P. C. Turtle, D. P. Strommen, B. Streusend, J. Kincaid and K. Nakamoto, Inorg. Chem., 1977, 16, 84.
27. A. J. Carty and P. C. Chieh, J. Chem. Soc., Chem. Commun., 1972, 158; M. Hinamoto, S. Ooi and H. Kuroya, J. Chem. Soc., Chem. Commun., 1972, 356.
28. H. W. Smith, B. D. Santasiero and E. C. Lingafelter, Cryst. Struct. Commun., 1979, 8, 49; L. E. McCandlish, B. D. Santassiero, N. J. Rose and E. C. Lingafelter, Acta Crystallogr., Sect. B, 1979, 35, 3053; V. L. Goedken, Y.-E. Park, S. M. Peng and J. Molin-Norris, J. Am. Chem. Soc., 1974, 96, 7693.
29. J. P. Jesson, S. Trofimenko and D. R. Eaton, J. Am. Chem. Soc., 1967, 89, 3158; M. A. Hoselton, L. J. Wilson and R. S. Drago, J. Am. Chem. Soc., 1975, 97, 1722; H. L. Chum, J. A. Vanin and M. I. D. Holanda, Inorg. Chem., 1982, 21, 1146.
30. R. G. Wilkins, The Study of Kinetics and Mechanism of Reactions of Transition Metal Complexes, Allyn and Bacon, Boston, 1974, ch. 7.
31. R. J. Abraham, S. C. M. Fell and K. M. Smith, Org. Magn. Reson., 1977, 9, 367.
32. R. A. D. Wentworth and T. S. Piper, Inorg. Chem., 1965, 4, 709.
33. S. S. Fielder, M. C. Osborne, A. B. P. Lever and W. J. Pietro, J. Am. Chem. Soc., 1995, 117, 6990.