Generation of manganese-(III) versus -(IV) complexes with a conjugated ONS donor set: controlling effect of ligand substituents †

Abstract

Manganese(IV) complexes, [MnL₂] [H₂L = MeC(OH)=CHCMe=NN= C(SH)SR (R = Me 1a or CH₂Ph 1b)] and manganese(III) complexes, [Mn(O₂CMe)L] 1c or [Mn(acac)L] 1d [acac = acetylacetonate; H₂L = PhCH(OH)CPh=NN=C(SH)SCH₂Ph] have been synthesized and characterized. The Schiff-base ligands which are derived from an aliphatic carbonyl function, favour the facile oxidation of manganese-(II) to -(IV) under ambient conditions. The structure determination of 1a showed that the molecule is octahedral with the two equivalent tridentate ligands spanned meridionally. The EPR spectrum of 1a with a strong but structured signal at g ≈ 4.0 and a weak one at g ≈ 2.0 implies a large zero-field splitting, but the spectral profile differed from an ideal axial form. All the complexes exhibited reversible or quasi-reversible Mn^IV–Mn^III redox couples in their cyclic voltammograms at potentials commensurate with the nature of the substituents in the appropriate ligands. A reasonable basis is suggested by which one may predict whether a particular ligand will stabilize manganese-(II), -(III) or -(IV) in an aerobic medium.

References

1. K. Wieghardt, Angew. Chem., Int. Ed. Engl., 1989, 28, 1153 and refs. therein.
2. J. B. Vincent and G. Christou, Adv. Inorg. Chem., 1989, 33, 197.
3. K. Sauer, Acc. Chem. Res., 1980, 13, 249.
4. K. A. Ahrling and R. J. Pace, Biophys. J., 1995, 68, 2081; D. W. Randell, B. E. Sturgeon, J. A. Ball, G. A. Lorigan, M. K. Chan, M. P. Klein, W. H. Armstrong and R. D. Britt, J. Am. Chem. Soc., 1995, 117, 11 780.
5. O. Hansson, A. Aasa and T. Vanngard, Biophys. J., 1987, 51, 825.
6. B. Frank, G. Dunkelmann and H. J. Lubs, Angew. Chem., Int. Ed. Engl., 1967, 6, 1075; P. A. Chaloner, Handbook of Coordination Catalysis in Organic Chemistry, Butterworths, London, 1986.
7. (a) J. R. Hartman, B. M. Foxman and S. R. Cooper, Inorg. Chem., 1984, 23, 1381; (b) S. K. Chandra, P. Basu, D. Ray and A. Chakravorty, Inorg. Chem., 1990, 29, 2423; (c) S. Dutta, P. Basu and A. Chakravorty, Inorg. Chem., 1991, 30, 4031; (d) S. M. Saadeh, M. S. Lah and V. L. Pecoraro, Inorg. Chem., 1991, 30, 8; (e) S. K. Chandra and A. Chakravorty, Inorg. Chem., 1992, 31, 760.
8. J. S. Bashkin, J. C. Huffman and G. Christou, J. Am. Chem. Soc., 1986, 108, 5038.
9. W. Zhang, J. L. Loebach, S. R. Wilson and E. N. Jacobson, J. Am. Chem. Soc., 1990, 112, 2801; R. S. Drago, Coord. Chem. Rev., 1992, 117, 185 and refs. therein.
10. M. N. Bhattacharjee, M. K. Chaudhuri and R. N. Dutta Purkayastha, Inorg. Chem., 1989, 28, 3747 and refs. therein.
11. J. C. Vites and M. M. Lynam, Coord. Chem. Rev., 1994, 131, 95; 1995, 138, 1.
12. R. Mukhopadhyay, S. Bhattacharjee and R. Bhattacharyya, J. Chem. Soc., Dalton Trans., 1994, 2799.
13. M. G. B. Drew, C. J. Harding, V. Mckee, G. G. Morgan and J. Nelson, J. Chem. Soc., Chem. Commun., 1995, 1035.
14. R. Mukhopadhyay, A. B. Chatterjee and R. Bhattacharyya, Polyhedron, 1992, 11, 1353.
15. R. Mukhopadhyay, S. Bhattacharjee and R. Bhattacharyya, unpublished work.
16. M. A. Ali and R. Bose, J. Inorg. Nucl. Chem., 1977, 39, 265.
17. S. Bhattacharjee and R. Bhattacharyya, J. Chem. Soc., Dalton Trans., 1993, 1151; 1992, 1357.
18. M. A. Ali, Can. J. Chem., 1980, 58, 727.
19. J. E. Kovacic, Spectrochim. Acta., Part A, 1967, 23, 183.
20. S. A. Boyd, R. E. Kohrman and D. X. West, J. Inorg. Nucl. Chem., 1976, 38, 607.
21. V. B. Rana, J. N. Gurtu and M. P. Teotia, J. Inorg. Nucl. Chem., 1980, 42, 331.
22. P. C. Healy and A. H. White, J. Chem. Soc., Dalton Trans., 1972, 1883.
23. K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley-Interscience, New York, 1978.
24. S. Pinchas, B. L. Silver and I. J. Laulicht, J. Chem. Phys., 1967, 46, 1056; H. Musso and H. Junge, Tetrahedron Lett., 1966, 33, 4003; 4009.
25. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, Wiley Eastern, New Delhi, 3rd edn., 1976, p. 624.
26. M. J. Camenzind, F. J. Hollander and C. L. Hill, Inorg. Chem., 1983, 22, 3776.
27. K. D. MaJers, C. G. Smith and D. T. Sawyer, Inorg. Chem., 1980, 19, 492.
28. D. T. Richens and D. T. Sawyer, J. Am. Chem. Soc., 1979, 101, 3681.
29. S. Pal, P. Ghosh and A. Chakravorty, Inorg. Chem., 1985, 24, 3704.
30. K. L. Brown, R. M. Golding, P. C. Healy, K. J. Jessop and W. C. Tennant, Aust. J. Chem., 1974, 27, 2075.
31. M. Koikawa, H. Okawa and S. Kida, J. Chem. Soc., Dalton Trans., 1988, 641.
32. L. J. Boucher and M. O. Farrell, J. Inorg. Nucl. Chem., 1973, 35, 3731.
33. C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976.
34. J. March, Advanced Organic Chemistry, Wiley-Interscience, New York, 1985.
35. M. K. Chan and W. H. Armstrong, Inorg. Chem., 1989, 28, 3777.
36. D. P. Kessissoglou, W. M. Butler and V. L. Pecoraro, J. Chem. Soc., Chem. Commun., 1986, 1253.
37. P. Deplano, F. Trogu, F. Bigoli and M. A. Pellinghelli, J. Chem. Soc., Dalton Trans., 1987, 2407.
38. K. Yamaguchi and D. T. Sawyer, Inorg. Chem., 1985, 24, 971.
39. M. A. Ali, S. E. Livingstone and D. J. Phillips, Inorg. Chim. Acta, 1973, 7, 179.
40. M. A. Ali and M. T. H. Tarafdar, J. Inorg. Nucl. Chem., 1977, 39, 1785.
41. D. D. Perrin, W. L. F. Armergo and D. R. Perrin, Purification of Laboratory Chemicals, Pergamon, New York, 1966.
42. D. T. Sawyer and J. L. Roberts, jun., Experimental Electrochemistry for Chemists, Wiley, New York, 1974, p. 167.
43. A. I. Vogel, A Text Book of Quantitative Inorganic Analysis, The English Language Book Society and Longman, London, 1968.
44. M. T. H. Tarafdar and M. A. Ali, Can. J. Chem., 1978, 56, 2000.
45. A. C. T. North, D. C. Phillips and F. S. Mathews, Acta Crystallogr., Sect. A, 1968, 24, 351.
46. G. M. Sheldrick, SHELXTL PLUS 90, Structure Determination Software Programs, Siemens Analytical X-Ray Instruments, Madison, WI, 1990.