Copper(I) and silver(I) complexes of a new tetrahedrally-enforcing ligand containing two bipyridyl binding sites linked by a diphenyl disulfide bridge

Abstract

Conversion of the amino group of 6-(2-aminophenyl)-2,2′-bipyridine to a thiol resulted not in the expected N,N,S-terdentate chelating ligand HL [6-(2-sulfhydryl)-2,2′-bipyridine] but in the oxidised disulfide 2,2′-bis[6-(2,2′-bipyridyl)]diphenyldisulfide, L–L. This ligand contains two bipyridyl arms linked by a diphenyl disulfide bridge in such a way that they cannot be coplanar, but tend to co-ordinate to a single metal ion with a substantial dihedral angle between the two ligand planes giving a pseudo-tetrahedral geometry. The crystal structure of L–L·0.5C₆H₅CH₃ shows the presence of near-linear N · · ·   S–S interactions (non-bonded N · · ·   S; 2.75 Å) in which the pyridyl lone pair interacts with the σ* orbital of the disulfide fragment. The complexes [Cu(L–L)][PF₆] and [Ag(L–L)][PF₆] were prepared and are isostructural, both having a distorted four-co-ordinate metal co-ordination environment in which the two chelating bipyridyl fragments have dihedral angles of between 70 and 80 °C between them (i.e. nearly mutually perpendicular). The electronic spectrum of the Cu^I complex [Cu(L–L)][PF₆], and the EPR spectrum of its one-electron oxidised product [Cu(L–L)]²⁺, both confirm that the rigidity of the ligand donor set does not permit much variation in the co-ordination environment about the copper ion. The ligand therefore imposes a relatively rigid pseudo-tetrahedral geometry on the metal centres.

References

1. J. A. Connor, M. Charlton, D. C. Cupertino, A. Lienke, M. McPartlin, I. J. Scowen and P. A. Tasker, J. Chem. Soc., Dalton Trans., 1996, 2835.
2. J. McMaster, R. L. Beddoes, D. Collison, D. R. Eardley, M. Helliwell and C. D. Garner, Chem. Eur. J., 1996, 2, 685; E. Müller, G. Bernardinelli and J. Reedijk, Inorg. Chem., 1996, 35, 1952; S. Knapp, T. P. Keenan, X. Zhang, R. Fikar, J. A. Potenza and H. J. Schugar, J. Am. Chem. Soc., 1990, 112, 3452; J. A. Goodwin, L. J. Wilson, D. M. Stanbury and R. A. Scott, Inorg. Chem., 1989, 28, 42.
3. Y. Wang and T. D. P. Stack, J. Am. Chem. Soc., 1996, 118, 13097.
4. W. M. Davis, A. Zask, K. Nakanishi and S. J. Lippard, Inorg. Chem., 1985, 24, 3737; M. Hirotsu, M. Kojima, K. Nakajima, S. Kashino and Y. Yoshikawa, Chem. Lett., 1994, 2183; S. Mandal and P. K. Bharadwaj, Polyhedron, 1993, 12, 543; E. M. Martin, R. D. Bereman and P. Singh, Inorg. Chem., 1991, 30, 957.
5. J. K. Judice, S. J. Keipert and D. J. Cram, J. Chem. Soc., Chem. Commun., 1993, 1323.
6. G. J. Kubas, Inorg. Synth., 1979, 19, 90.
7. A. M. W. Cargill Thompson, D. A. Bardwell, J. C. Jeffery and M. D. Ward, Inorg. Chim. Acta, in the press.
8. A. M. W. Cargill Thompson, D. A. Bardwell, J. C. Jeffery, L. H. Rees and M. D. Ward, J. Chem. Soc., Dalton Trans., 1997, 721.
9. D. McKinnon, K. A. Duncan, A. M. McKinnon and P. A. Spevack, Can. J. Chem., 1985, 63, 882.
10. P. L. Jones, A. J. Amoroso, J. C. Jeffery, J. A. McCleverty, E. Psillakis, L. H. Rees and M. D. Ward, Inorg. Chem., 1997, 36, 10.
11. SHELXTL 5.03 program system, Siemens Analytical X-Ray Instruments, Madison, WI, USA, 1995.
12. D. A. Bardwell, A. M. W. Cargill Thompson, J. C. Jeffery, E. E. M. Tilley and M. D. Ward, J. Chem. Soc., Dalton Trans., 1995, 835.
13. D. A. Bardwell, J. C. Jeffery, E. Schatz, E. E. M. Tilley and M. D. Ward, J. Chem. Soc., Dalton Trans., 1996, 825; D. A. Bardwell, J. G. Crossley, J. C. Jeffery, A. G. Orpen, E. Psillakis, E. E. M. Tilley and M. D. Ward, Polyhedron, 1994, 13, 2291.
14. R. E. Rosenfeld, jun., R. Parthasarathy and J. D. Dunitz, J. Am. Chem. Soc., 1977, 99, 4860; F. T. Burling and B. M. Goldstein, J. Am. Chem. Soc., 1992, 114, 2313; F. T. Burling and B. M. Goldstein, Acta Crystallogr., Sect. B, 1993, 49, 738; G. R. Desiraju and V. Nalini, J. Mater. Chem., 1991, 1, 201; D. Britton and J. D. Dunitz, Helv. Chim. Acta, 1980, 63, 1068; M. Iwaoka and S. Tomoda, J. Am. Chem. Soc., 1996, 118, 8077.
15. P. J. Burke, D. R. McMillin and W. R. Robinson, Inorg. Chem., 1980, 19, 1211; M. Geoffroy, M. Wermeille, C. O. Buchecker, J.-P. Sauvage and G. Bernardinelli, Inorg. Chim. Acta, 1990, 167, 157; M. Cesario, C. O. Dietrich-Buchecker, T. Guilhem, C. Pascard and J.-P. Sauvage, J. Chem. Soc., Chem. Commun., 1985, 244; K. Klemens, C. E. A. Palmer, S. M. Rolland, P. E. Fanwick, D. R. McMillin and J.-P. Sauvage, New J. Chem., 1990, 14, 129; R. Hämäläinen, M. Ahlgren, U. Terpeinen and T. Raikas, Crystallogr. Struct. Commun., 1979, 8, 75; D. A. Bardwell, J. C. Jeffery, C. A. Otter and M. D. Ward, Polyhedron, 1996, 15, 191.
16. K. V. Goodwin, D. R. McMillin and W. R. Robinson, Inorg. Chem., 1986, 25, 2033.
17. A. K. Ichinaga, J. R. Kirchhoff, D. R. McMillin, C. O. Dietrich-Buchecker, P. A. Marnot and J.-P. Sauvage, Inorg. Chem., 1987, 26, 4290.
18. M. A. Masood and P. S. Zacharias, J. Chem. Soc., Dalton Trans., 1991, 111.
19. P. Federlin, J.-M. Kern, A. Rastegar, C. O. Dietrich-Buchecker, P. A. Marnot and J.-P. Sauvage, New J. Chem., 1990, 14, 9.
20. N. G. Connelly and W. E. Geiger, Chem. Rev., 1996, 96, 877.
21. F. G. Herring, D. J. Patmore and A. Storr, J. Chem. Soc., Dalton Trans., 1975, 711; D. J. Patmore, D. F. Rendle, A. Storr and J. Trotter, J. Chem. Soc., Dalton Trans., 1975, 718.
22. W. M. Davis, A. Zask, K. Nakanishi and S. J. Lippard, Inorg. Chem., 1985, 24, 3737; D. Attanasio, A. A. G. Tomlinson and L. Alagna, J. Chem. Soc., Chem. Commun., 1977, 618; R. J. Dudley, B. J. Hathaway and P. G. Hodgson, J. Chem. Soc., Dalton Trans., 1972, 882.
23. J. Foley, S. Tyagi and B. J. Hathaway, J. Chem. Soc., Dalton Trans., 1984, 1.