Diphenoxo-bridged NiCo and CuCo complexes of macrocyclic ligands: synthesis, structure and electrochemical behaviour

Abstract

Heterodinuclear di-µ-phenoxo-M^IICo^II (M = Ni or Cu) complexes have been derived from phenol-based dinucleating ligands (L^m,n)^2-, comprising of two 2,6-di(iminomethyl)-4-methylphenolate entities linked by two lateral chains (CH₂)_m (m = 2 or 3) and (CH₂)_n (n = 3 or 4) at the imino nitrogens. The crystal structure of [CuCo(L^2,3)(dmf )₂(H₂O)][ClO ₄]₂ (dmf = dimethylformamide) has been determined. The copper ion resides at the N₂O₂ site formed by the ethylene lateral chain and assumes a square-pyramidal geometry together with a dmf oxygen at the apex. The Co at the site of the trimethylene lateral chain assumes a pseudo-octahedral geometry together with a dmf and a water molecule at the axial positions. The Cu · · ·   Co separation doubly bridged by the phenolic oxygens is 2.998(2) Å. The NiCo complexes are paramagnetic (S_Ni = 0), whereas the CuCo complexes show a strong antiferromagnetic interaction between the two metal ions. Cyclic voltammograms of the NiCo complexes show two quasi-reversible couples attributable to the stepwise reductions: Ni^IICo^II → Ni^ICo ^II → Ni^ICo^I. The Ni^ICo^II and Ni^ICo^I complexes were prepared in solution by coulometry and characterized by visible spectroscopy. Similarly, the CuCo complex of (L^3,3)^2- is reduced stepwise to Cu^ICo^II and then to Cu^ICo^I. On the other hand, the CuCo complexes of (L^2,3)^2- and (L^2,4)^2- showed unusual electrochemical behaviour at the electrode suggesting a scrambling or site exchange of the metal ions.

References

1. O. Kahn, Struct. Bonding (Berlin), 1987, 68, 89.
2. P. Zanello, S. Tamburini, P. A. Vigato and G. A. Mazzocchin, Coord. Chem. Rev., 1987, 77, 165.
3. P. A. Vigato, S. Tamburini and D. E. Fenton, Coord. Chem. Rev., 1990, 106, 25.
4. N. Sträter, T. Klabunde, P. Tucker, H. Witzel and B. Krebs, Science, 1995, 268, 1489.
5. C. R. Kissinger, H. E. Parge, D. R. Knighton, C. T. Lewis, L. A. Pelletier, A. Tempczyk, V. J. Kalish, K. D. Tucker, R. E. Showalter, E. W. Moomaw, L. N. Gastinel, N. Habuka, X. Chen, F. Maldonado, J. E. Barker, R. Bacquet and J. E. Villafranca, Nature (London), 1995, 378, 641.
6. M.-P. Egloff, P. T. W. Cohen, P. Reinemer and D. Barford, J. Mol. Biol., 1995, 254, 942.
7. D. E. Fenton and H. Ōkawa, Chem. Ber., 1997, 130, 433.
8. H. Ōkawa and S. Kida, Inorg. Nucl. Chem. Lett., 1971, 7, 751; Bull. Chem. Soc. Jpn., 1972, 45, 1759.
9. M. Tadokoro, H. Ōkawa, N. Matsumoto, M. Koikawa and S. Kida, J. Chem. Soc., Dalton Trans., 1991, 1657; M. Tadokoro, H. Sakiyama, N. Matsumoto, M. Kodera, H. Ōkawa and S. Kida, J. Chem. Soc., Dalton Trans., 1992, 313.
10. H. Ōkawa, J. Nishio, M. Ohba, M. Tadokoro, N. Matsumoto, M. Koikawa, S. Kida and D. E. Fenton, Inorg. Chem., 1993, 32, 2949; J. Nishio, H. Ōkawa, S. Ohtsuka and M. Tomono, Inorg. Chim. Acta, 1994, 218, 27; J. Shimoda, H. Furutachi, M. Yonemura, M. Ohba, N. Matsumoto and H. Ōkawa, Chem. Lett., 1996, 979.
11. S. Ohtsuka, M. Kodera, K. Motoda, M. Ohba and H. Ōkawa, J. Chem. Soc., Dalton Trans., 1995, 2599.
12. M. Yonemura, Y. Matsumura, M. Ohba, H. Ōkawa and D. E. Fenton, Chem. Lett., 1996, 601.
13. C. Fraser, S. L. Johnston, A. L. Rheingold, B. S. Haggerty, G. K. Williams, J. Whelan and B. Bosnich, Inorg. Chem., 1992, 31, 1835; D. G. McCollum, G. P. A. Yap, A. L. Rheingold and B. Bosnich, J. Am. Chem. Soc., 1996, 118, 1365 and refs. therein.
14. S. Karunakaran and M. Kandaswamy, J. Chem. Soc., Dalton Trans., 1994, 1595.
15. N. H. Pilkington and R. Robson, Aust. J. Chem., 1970, 23, 2225; B. F. Hoskins, R. Robson and G. A. Williams, Aust. J. Chem., 1975, 28, 2598; Inorg. Chim. Acta, 1975, 29, 2607; 1976, 16, 16, 121.
16. N. F. Curtis, J. Chem. Soc., 1961, 3147.
17. E. A. Boudreaux and L. N. Mulay, Theory and Applications of Molecular Paramagnetism, Wiley, New York, 1976, pp. 491–494.
18. D. A. Denton and H. Suschitzky, J. Chem. Soc., 1963, 4741.
19. D. T. Cromer and J. T. Waber, International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. 4.
20. D. C. Creagh and W. J. McAuley, in International Tables for Crystallography, Kluwer, Boston, 1992, vol. C.
21. D. C. Creagh and H. H. Hubbell, in International Tables for Crystallography, Kluwer, Boston, 1992, vol. C.
22. TEXSAN, Molecular Structure Corporation, Houston, TX, 1985.
23. R. R. Gagne, C. L. Spiro, T. J. Smith, C. A. Hamann, W. R. Thies and A. K. Shiemke, J. Am. Chem. Soc., 1981, 103, 4073.
24. B. V. Crook, H. Doine, F. F. Stephens, M. J. Cannon and R. D. Cannon, Polyhedron, 1989, 8, 2007.
25. B. Bosnich, J. Am. Chem. Soc., 1968, 90, 627.
26. R. S. Downing and F. L. Urbach, J. Am. Chem Soc., 1968, 90, 627.
27. S. M. Crawford, Spectrochim. Acta, 1963, 19, 225.
28. C. K. Johnson, ORTEP, Report 3794, Oak Ridge National Laboratory, Oak Ridge, TN, 1965.
29. H. Wada, T. Aono, K. Motoda, M. Ohba, N. Matsumoto and H. Ōkawa, Inorg. Chim. Acta, 1996, 246, 13.
30. H. Wada, K. Motoda, M. Ohba, H. Sakiyama, N. Matsumoto and H. Ōkawa, Bull. Chem. Soc. Jpn., 1995, 68, 1105.
31. M. P. Sue, H. K. Kim, M. J. Kim and K. Y. Oh, Inorg. Chem., 1992, 31, 3620.
32. H. Ōkawa, Y. Aratake, K. Motoda, M. Ohba, H. Sakiyama and N. Matsumoto, J. Supramol. Chem., 1996, 6, 293.
33. H. Wada, T. Aono, K. Motoda, M. Ohba, H. Matsumoto and H. Ōkawa, Inorg. Chim. Acta, 1996, 246, 13.
34. H. Ōkawa and D. H. Busch, Inorg. Chem., 1979, 18, 1555.
35. Y. Nishida and S. Kida, Coord. Chem. Rev., 1979, 27, 275.
36. R. C. Long and D. N. Hendrickson, J. Am. Chem. Soc., 1983, 105, 1513.
37. A. W. Addison, Inorg. Nucl. Chem. Lett., 1976, 12, 899.