Six-co-ordinated vanadium-(IV) and -(V) complexes of benzimidazole and pyridyl containing ligands

Abstract

A new series of vanadium-(IV) and -(V) complexes with ligands containing functionalities including hydroxyethyl, carboxylate, amine, pyridyl and benzimidazole have been prepared. The crystal structures of three complexes have been determined. All the vanadium atoms are six-co-ordinate even though previous complexes of the diethanolamine type have contained five-co-ordinate vanadium. The V–N (amine) bonds of the benzimidazole complexes are significantly longer than those of pyridyl complexes. An empirical relationship between pK_a value of the protonated ligand and the V–N (amine) bond length (trans to an oxo group) of the corresponding vanadium-(IV), -(V) and -(IV/V) complexes was observed. Spectroscopic studies (NMR, ESR and UV/VIS) showed that the complexes remain intact in aqueous solution. In general, the hydroxyethyl substituted vanadium complexes are less stable than corresponding acetate substituted ones and the benzimidazole complexes are less stable than corresponding pyridyl complexes. The combined knowledge concerning the properties of all these complexes provides an excellent platform to design new vanadium complexes pertinent to biological applications.

References

1. D. C. Crans, M. Mahroof-Tahir, P. K. Shin and A. D. Keramidas, Mol. Cell. Biochem., 1995, 153, 17.
2. A. Messerschmidt and R. Wever, Proc. Natl. Acad. Sci. USA, 1996, 93, 392.
3. D. C. Crans, H. Chen, O. P. Anderson and M. M. Miller, J. Am. Chem. Soc., 1993, 115, 6769.
4. K. Kustin and D. L. Toppen, J. Am. Chem. Soc., 1973, 95, 3564.
5. P. K. Shin, Ph.D. Thesis, Colorado State University, 1993.
6. D. C. Crans and P. K. Shin, Inorg. Chem., 1988, 27, 1797.
7. D. C. Crans, P. M. Ehde, P. K. Shin and L. Pettersson, J. Am. Chem. Soc., 1991, 113, 3728.
8. D. C. Crans and P. K. Shin, J. Am. Chem. Soc., 1994, 116, 1305.
9. D. C. Crans, A. D. Keramidas, M. Mahroof-Tahir, O. P. Anderson and M. M. Miller, Inorg. Chem., 1996, 35, 3599.
10. D. C. Crans and I. Boukhobza, unpublished work.
11. W. Plass, Inorg. Chim. Acta, 1996, 244, 221.
12. M. Mahroof-Tahir, A. D. Keramidas, R. B. Goldfarb, O. P. Anderson, M. M. Miller and D. C. Crans, Inorg. Chem., 1997, 36, 1657.
13. S. Ooi, M. Nishizawa, K. Matsumoto, H. Kuroya and K. Saito, Bull. Chem. Soc. Jpn., 1979, 52, 452.
14. K. Okazaki and K. Saito, Bull. Chem. Soc. Jpn., 1982, 55, 785.
15. H. Irving and J. J. R. F. da Silva, J. Chem. Soc., 1963, 945.
16. L. A. Cescon and A. R. Day, J. Org. Chem., 1962, 27, 581.
17. J. G. Wilson and F. C. Hunt, Aust. J. Chem., 1983, 36, 2317.
18. B. Bleaney, Philos. Mag., 1951, 42, 441.
19. N. D. Chasteen, Biological Magnetic Resonance, ed. J. Reuben, Plenum Press, New York, 1981, 53.
20. G. M. Sheldrick, SHELXTL, version 5.03, Siemens Analytical X-Ray Instruments, Madison, WI, 1994.
21. International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1992, vol. 4.
22. M. Nishizawa, K. Hirotsu, S. Ooi and K. Saito, J. Chem. Soc., Chem. Commun., 1979, 707.
23. W. R. Scheidt, R. Countryman and J. L. Hoard, J. Am. Chem. Soc., 1971, 93, 3878.
24. Z. Kangjing and L. Xiaoping, J. Struct. Chem., 1987, 6, 14.
25. A. D. Keramidas, S. M. Miller, O. P. Anderson and D. C. Crans, J. Am. Chem. Soc., 1997, in the press.
26. A. Neves, W. Walz, K. Wieghardt, B. Nuber and J. Weiss, Inorg. Chem., 1988, 27, 2484.
27. D. Schulz, T. Weyhermüller, K. Wieghardt and B. Nuber, Inorg. Chim. Acta, 1995, 240, 217.
28. K. Takahashi and Y. Nishida, Z. Naturforsch., Teil B, 1987, 42, 1307.
29. C. G. Barraclough, J. Lewis and R. S. Nyholm, J. Chem. Soc., 1959, 3552.
30. W. P. Griffith and T. D. Wickins, J. Chem. Soc. A, 1968, 400.
31. L. W. Amos and D. T. Sawyer, Inorg. Chem., 1972, 11, 2692.
32. E. de Boer, K. Boon and R. Wever, Biochemistry, 1988, 27, 1629.
33. D. D. Perrin and B. Dempsey, Buffers for pH and Metal Ion Control, ed. D. D. Perrin and B. Dempsey, Chapman and Hall, New York, 1974.
34. (a) D. Rehder, Bull. Magn. Reson., 1982, 4, 33; (b) D. C. Crans, P. K. Shin and K. B. Armstrong, Mechanistic Bioinorganic Chemistry, eds. H. Thorp and V. Pecoraro, American Chemical Society, Washington, DC, 1995, 303.
35. K. Kustin, S.-T. Liu, C. Nicolini and D. L. Toppen, J. Am. Chem. Soc., 1974, 96, 7410.
36. K. Kustin, C. Nicolini and D. L. Toppen, J. Am. Chem. Soc., 1974, 96, 7416.
37. F. Babonneau, C. Sanchez, J. Livage, J. P. Launay, M. Daoudi and Y. Jeannin, Nouv. J. Chim., 1982, 6, 353.