Factors affecting the rate of ligand substitution reactions of aquacobalamin (vitamin B12a)[hair space]

(Note: The full text of this document is currently only available in the PDF Version )

Helder M. Marques and Leanne Knapton


Abstract

The ligand substitution reactions of co-ordinated H2O in aquacobalamin (vitamin B12) by OCN, SCN, SeCN, NO2, S2O32– and N3 in a NaNO3 medium, in contrast to an earlier report on some of these ligands in a KCl medium, proceeded too rapidly for saturation kinetics to be observed. The discrepancy, as suggested previously, is due to formation of a significant fraction of the more substitution-inert chloro complex in a KCl medium. Second-order rate constants, corrected for pH effects, for the reactions have been determined as a function of temperature, from which activation parameters were calculated. The identity of the donor atom of the ambidentate ligands in the rate-determining processes, kII, is considered and correlations found between ΔH[hair space] kII, the enthalpy of activation, and ΔS[hair space] kII, the entropy of activation, respectively, the Mulliken population on the donor atom, and the energy of the highest occupied molecular orbital (HOMO) with σ symmetry. The parameters ΔH[hair space] kII is strongly dependent on the HOMO energy, and more weakly dependent on the electron density on the donor atom, while the converse is true for ΔS[hair space] kII.


References

  1. W. C. Randall and R. A. Alberty, Biochemistry, 1966, 5, 3189 CrossRef CAS.
  2. W. C. Randall and R. A. Alberty, Biochemistry, 1967, 6, 1520 CrossRef CAS.
  3. D. Thusius, J. Am. Chem. Soc., 1971, 93, 2629 CrossRef CAS.
  4. C. K. Poon, Coord. Chem. Rev., 1973, 10, 1 CrossRef.
  5. F. Nome and J. H. Fendler, J. Chem. Soc., Dalton Trans., 1976, 1212 RSC.
  6. D. A. Baldwin, E. A. Betterton and J. M. Pratt, S. Afr. J. Chem., 1982, 35, 173 Search PubMed.
  7. G. Stochel, R. van Eldik, H. Kunkley and A. Vogler, Inorg. Chem., 1989, 28, 4314 CrossRef CAS.
  8. G. Stochel and R. van Eldik, Inorg. Chem., 1990, 29, 2075 CrossRef CAS.
  9. W. W. Reenstra and W. P. Jencks, J. Am. Chem. Soc., 1979, 101, 5780 CrossRef CAS.
  10. H. M. Marques, K. L. Brown and D. W. Jacobsen, J. Biol. Chem., 1988, 263, 123 78 CAS.
  11. H. M. Marques, T. J. Egan, J. H. Marsh, J. R. Mellor and O. Q. Munro, Inorg. Chim. Acta, 1989, 166, 249 CrossRef CAS.
  12. H. M. Marques, J. Chem. Soc., Dalton Trans., 1991, 1437 RSC.
  13. H. M. Marques, J. Chem. Soc., Dalton Trans., 1991, 339 RSC.
  14. H. M. Marques, E. L. J. Breet and F. F. Prinsloo, J. Chem. Soc., Dalton Trans., 1991, 2941 RSC.
  15. H. M. Marques, J. C. Bradley and L. A. Campbell, J. Chem. Soc., Dalton Trans., 1992, 2019 RSC.
  16. H. M. Marques, J. C. Bradley, K. L. Brown and H. Brooks, J. Chem. Soc., Dalton Trans., 1993, 3475 RSC.
  17. H. M. Marques, O. Q. Munro, B. M. Cumming and C. de Nysschen, J. Chem. Soc., Dalton Trans., 1994, 297 RSC.
  18. J. J. P. Stewart, J. Comput. Chem., 1989, 10, 209 CrossRef CAS.
  19. J. J. P. Stewart, J. Comput. Chem., 1989, 10, 221 CrossRef CAS.
  20. F. F. Prinsloo, E. L. J. Breet and R. van Eldik, J. Chem. Soc., Dalton Trans., 1995, 685 RSC.
  21. J. B. Conn and T. G. Wartman, Science, 1952, 115, 72 CAS.
  22. K. L. Brown, S. Cheng, X. Zou, J. D. Zubkowski, E. J. Valente, L. Knapton and H. M. Marques, Inorg. Chem., 1997, 36, 3666 CrossRef CAS.
  23. HYPERCHEM, Molecular Visualization and Simulation, V. 4.5, Hypercube Inc., Waterloo, Ontario, 1995.
  24. J. B. Collins, P. V. Schleyer, J. S. Binkley and J. A. Pople, J. Chem. Phys., 1976, 64, 5142 CrossRef CAS.
  25. R. C. Raffenetti, Chem. Phys. Lett., 1973, 20, 335 CrossRef CAS.
  26. F. F. Prinsloo, M. Meier and R. van Eldik, Inorg. Chem., 1994, 33, 900 CrossRef CAS.
  27. M. S. Searle, M. S. Westwell and D. H. Williams, J. Chem. Soc., Perkin Trans. 2, 1995, 141 RSC.
  28. J. A. Shelnutt, J. Phys. Chem., 1983, 87, 605 CrossRef CAS; J. Am. Chem. Soc., 1981, 103, 4275 Search PubMed; J. Am. Chem. Soc., 1983, 105, 774 Search PubMed; Inorg. Chem., 1983, 22, 2535 Search PubMed.
  29. J. P. Glusker, in B12, ed. D. Dolphin, Wiley, New York, 1982, vol. 1, p. 23 Search PubMed.
  30. A. H. Norbury, Adv. Inorg. Chem. Radiochem., 1975, 17, 231 Search PubMed.
  31. J. L. Burmeister, Coord. Chem. Rev., 1990, 105, 77 CrossRef CAS.
  32. R. G. Pearson, Inorg. Chem., 1988, 27, 734 CrossRef CAS; J. Chem. Educ., 1987, 64, 561 Search PubMed; A. Beerbower and W. B. Jensen, Inorg. Chim. Acta, 1983, 75, 193 Search PubMed.
  33. A. M. Golub, H. Köhler and V. V. Skopenko, Chemistry of the Pseudohalides, Elsevier, Amsterdam, 1986 Search PubMed.
  34. D. F. Tuan, J. W. Reed and R. Hoffman, J. Mol. Struct. (THEOCHEM), 1991, 232, 111 CrossRef.
  35. C. Hedtmann-Rein, M. Hanack, K. Peters, E. M. Peters and H. G. von Schnering, Inorg. Chem., 1987, 26, 2647 CrossRef CAS.
  36. M. J. Maroney, E. O. Fey, D. A. Baldwin, R. E. Stenkamp, L. H. Jensen and N. J. Rose, Inorg. Chem., 1986, 25, 1409 CrossRef CAS.
  37. J. A. Kargol, K. D. Lavin, R. W. Crecely and J. L. Burmeister, Inorg. Chem., 1980, 19, 1515 CrossRef CAS.
  38. J. M. Pratt, The Inorganic Chemistry of Vitamin B12, Academic Press, London, 1972 Search PubMed.
  39. R. F. Pasternack and M. A. Cobb, J. Inorg. Nucl. Chem., 1973, 35, 4327 CrossRef CAS.
  40. A. J. Paviglianiti, D. J. Minn, W. C. Fultz and J. L. Burmeister, Inorg. Chim. Acta, 1989, 159, 65 CrossRef CAS; G. J. Palenik, M. Mathew, W. L. Steffen and G. Beran, J. Am. Chem. Soc., 1975, 97, 1059 CrossRef CAS; C. A. Grygon, W. C. Fultz, A. L. Rheingold and J. L. Burmeister, Inorg. Chim. Acta, 1988, 141, 31, 205 CrossRef.
  41. J. K. Das and K. C. Dash, Synth. React. Inorg. Metal-Org. Chem., 1985, 15, 839 Search PubMed.
  42. J. M. Pratt and R. G. Thorp, J. Chem. Soc. A, 1966, 187 RSC.
  43. D. C. Hodgkin, J. Kamper, J. Lindsay, M. McKay, J. Pickworth, J. H. Robertson, C. B. Shoemaker, J. G. White, R. J. Prosen and K. N. Trueblood, Proc. R. Soc. London, Ser. A, 1957, 242, 228.
  44. D. F. Tuan and R. Hoffman, Inorg. Chem., 1985, 24, 871 CrossRef CAS.
  45. R. G. Pearson, P. M. Henry, J. G. Bergmann and F. Basolo, J. Am. Chem. Soc., 1954, 76, 5920 CrossRef CAS; R. K. Murmann and H. Taube, J. Am. Chem. Soc., 1956, 78, 4886 CrossRef CAS.
  46. J. L. Burmeister, Coord. Chem. Rev., 1968, 3, 225 CrossRef.
Click here to see how this site uses Cookies. View our privacy policy here.