Nickel(II) N₂X₂ Schiff-base complexes incorporating pyrazole (X = NH, O or S): syntheses and characterization †

Abstract

A series of four-co-ordinate nickel(II) N₂X₂ complexes (X = NH, O or S) with tetradentate Schiff-base ligands incorporating pyrazole has been prepared in order to compare the influence on the nickel(II) centre of the donor atoms in N₂(NH)₂ and N₂S₂ complexes versus N₂O₂ complexes. In each case, two identical parts of the ligand are linked by a two- or three-carbon aliphatic chain (n = 2 or 3). Crystal structures have been determined for a n = 3 N₂(NH)₂ complex, for two n = 3 N₂S₂ complexes and for a n = 2 N₂O₂ complex. All of the complexes have been investigated in solution by spectroscopic methods (UV/VIS/NIR, ¹H NMR). The n = 2 and 3 N₂(NH)₂ complexes and the n = 2 N₂S₂ complexes are fully diamagnetic. An extension of the chain linking the two halves of the ligand from two to three carbon atoms induces a spin-equilibrium process (S = 0 ⇄ S = 1) for the resulting N₂S₂ complex (ΔG = 19–26 kJ mol^–1 at 50 °C). Ligand-field parameters have been derived from the electronic spectra and the electrochemical properties of the N₂S₂ complexes have been investigated by cyclic voltammetry. From these results it is clear that low-spin character is emphasized in N₂(NH)₂ and N₂S₂ complexes of nickel(II) when compared with the corresponding N₂O₂ complexes.

References

1. (a) I. Y. Kvitko, L. V. Alam, N. I. Rtishchev, A. V. Eltsov, L. N. Kuriovskaya and N. B. Chebotareva, J. Gen. Chem. USSR, 1982, 2048; (b) A. la Cour, M. Findeisen, K. Hansen, R. Hazell, L. Hennig, C. E. Olsen, L. Petersen and O. Simonsen, J. Chem. Soc., Dalton Trans., 1997, 2045; (c) H. Toftlund, A. L. Nivorozhkin, A. la Cour, B. Adhikhari, K. S. Murray, G. D. Fallon and L. E. Nivorozhkin, Inorg. Chim. Acta, 1995, 228, 237; (d) V. P. Garnovskii, V. P. Kurbatov, B. A. Porai-Koshits, O. A. Osipov, I. Y. Kvitko, L. S. Minkina, E. M. Sofina and A. F. Soloshko-Doroshenko, J. Gen. Chem. USSR, 1970, 2326; (e) A. la Cour, M. Findeisen, A. Hazell, L. Hennig, G. Zdobinsky and O. Simonsen, unpublished work; (f) A. la Cour, B. Adhikhari, H. Toftlund and A. Hazell, Inorg. Chim. Acta, 1992, 202, 145; (g) A. D. Garnovskii, A. L. Nivorozhkin and V. I. Minkin, Coord. Chem. Rev., 1993, 126, 1.
2. (a) S. Yamada, Coord. Chem. Rev., 1966, 1, 415; (b) R. Knorr and A. Weiss, Chem. Ber., 1981, 114, 2104; (c) J. M. Fernandez-G., M. J. Rosales-Hoz, M. F. Rubio-Arroyo, R. Salcedo, F. Toscano and A. Vela, Inorg. Chem., 1987, 26, 349.
3. (a) D. H. Gerlach and R. H. Holm, J. Am. Chem. Soc., 1969, 91, 3457; (b) W. S. Sheldrick, R. Knorr and H. Polzer, Acta Crystallogr., Sect. B, 1979, 35, 739; (c) M. Schumann and H. Elias, Inorg. Chem., 1985, 24, 3187; (d) E. Uhlemann, G. Hinsche, H. Braunschweig and M. Weissenfels, Z. Anorg. Allg. Chem., 1970, 377, 321; (e) I. Bertini, L. Sacconi and G. P. Speroni, Inorg. Chem., 1972, 11, 1323.
4. (a) V. A. Kogan, N. N. Kharabaev, O. A. Osipov and S. G. Kochin, J. Struct. Chem., 1981, 22, 96; (b) O. P. Anderson, J. Becher, H. Frydendahl, L. F. Taylor and H. Toftlund, J. Chem. Soc., Chem. Commun., 1986, 699; (c) C. T. Pedersen, Sulfur Rep., 1980, 1, 1; (d) C. T. Pedersen, Phosphorus Sulfur Silicon, Relat. Elem., 1991, 58, 17; (e) J. Roncali, L. Rasmussen, C. Thobie-Gautier, P. Frère, H. Brisset, M. Sallé, J. Becher, O. Simonsen, T. K. Hansen, A. Benahmed-Gasmi, J. Orduna, J. Garin, M. Jubault and A. Gorgues, Adv. Mater., 1994, 6, 841.
5. E. Frason, C. Panattoni and L. Sacconi, J. Phys. Chem., 1959, 63, 1908; S. C. Chang, D. Y. Park and N. C. Li, Inorg. Chem., 1968, 7, 2144; E. E. Castellano, O. J. R. Hodder, C. K. Prout and P. J. Sadler, J. Chem. Soc. A, 1971, 2620; L. L. Merritt, jun., C. Guaret and A. E. Lessor, jun., Acta Crystallogr., 1956, 9, 253.
6. (a) W. C. Hoyt and G. W. Everett, jun., Inorg. Chem., 1969, 8, 2030; (b) G. M. Mockler, G. W. Chaffey, E. Sinn and H. Wong, Inorg. Chem., 1972, 11, 1308; (c) M. A. A. F. de C. T. Carrondo, B. de Castro, A. M. Coelho, D. Doningues, C. Freire and J. Morais, Inorg. Chim. Acta, 1993, 205, 157; (d) M. Green and P. A. Tasker, J. Chem. Soc. A, 1970, 2531; (e) M. Green and P. A. Tasker, Inorg. Chim. Acta, 1971, 5, 65; (f) B. M. Higson and E. D. McKenzie, J. Chem. Soc. A, 1971, 269.
7. (a) L. Beyer, M. Pulst, H. R. Paul and E. Hoyer, J. Prakt. Chem., 1975, 317, 265; (b) H. S. Jensen, V. McKee and C. J. McKenzie, personal communication; (c) T. Yamamura, M. Tadokoro and R. Kuroda, Chem. Lett., 1989, 1246; (d) P. R. Blum, R. M. C. Wei and S. C. Cummings, Inorg. Chem., 1974, 13, 450; (e) D. Attanasio, G. Dessy, V. Fares and G. Pennesi, Mol. Phys., 1980, 40, 269.
8. (a) H. R. Engeseth, D. R. McMillin and E. L. Ulrich, Inorg. Chim. Acta, 1982, 67, 145; (b) M. J. O'Connor, R. E. Ernst and R. H. Holm, J. Am. Chem. Soc., 1968, 90, 4561; (c) M. J. O'Connor and R. H. Holm, Prog. Inorg. Chem., 1971, 14, 241; (d) H. Frydendahl, H. Toftlund, J. Becher, J. C. Dutton, K. S. Murray, L. F. Taylor, O. P. Anderson and E. R. T. Tiekink, Inorg. Chem., 1995, 34, 4467.
9. (a) A. la Cour, M. Findeisen, R. Hazell, L. Hennig, C. E. Olsen and O. Simonsen, J. Chem. Soc., Dalton Trans., 1996, 3437 and refs. Therein; (b) L. Hennig, R. Kirmse, O. Hammerich, S. Larsen, H. Frydendahl, H. Toftlund and J. Becher, Inorg. Chim. Acta, 1995, 234, 67.
10. A. N. Nivorozhkin, H. Toftlund, P. L. Jørgensen and L. E. Nivorozhkin, J. Chem. Soc., Dalton Trans., 1996, 1215.
11. A. la Cour, Ph. D. Thesis, Odense University, Odense, 1996.
12. (a) O. P. Anderson, A. la Cour, M. Findeisen, L. Hennig, L. F. Taylor, O. Simonsen and H. Toftlund, J. Chem. Soc., Dalton Trans., 1997, 111; (b) C. P. Brock and J. D. Dunitz, Chem. Mater., 1994, 6, 1118; (c) K. Bernardo, S. Leppard, A. Robert, G. Commenges, F. Dahan and B. Meunier, Inorg. Chem., 1996, 35, 387.
13. (a) F. Akhtar and M. G. B. Drew, Acta Crystallogr., Sect. B, 1982, 38, 1149; (b) M. G. B. Drew, R. N. Prasad and R. P. Sharma, Acta Crystallogr., Sect. C, 1985, 41, 1755; (c) F. Akhtar, Acta Crystallogr., Sect. B, 1981, 37, 84; (d) N. A. Bailey, E. D. McKenzie and J. M. Worthington, J. Chem. Soc., Dalton Trans., 1974, 1363; (e) E. M. Martin, R. D. Bereman and P. Singh, Inorg. Chem., 1991, 30, 957; (f) A. L. Nivorozhkin, L. E. Konstantinovsky, L. E. Nivorochkin, V. I. Minkin, T. G. Takhirov, O. A. Diachenko and D. B. Tagiev, Izv. Akad. Nauk SSSR, Ser. Khim., 1990, 327 (in Russian); (g) A. la Cour, M. Findeisen, A. Hazell, R. Hazell and G. Zdobinsky, J. Chem. Soc., Dalton Trans., 1997, 121.
14. (a) J. H. Weber, Inorg. Chem., 1967, 6, 258; (b) E. M. Martin, R. D. Bereman and J. Dorfman, Inorg. Chim. Acta, 1990, 176, 247; (c) E. M. Martin and R. D. Bereman, Inorg. Chim. Acta, 1991, 188, 221.
15. (a) M. Gerloch, Coord. Chem. Rev., 1990, 99, 117; (b) A. Ceulemans, M. Dendooven and L. G. Vanquickenborne, Inorg. Chem., 1985, 24, 1159.
16. A. B. P. Lever, Inorganic Electronic Spectroscopy, 2nd edn., Elsevier, Amsterdam, 1984, pp. 218–223.
17. (a) T. Yamamura, M. Tadokoro, M. Hamaguchi and R. Kuroda, Chem. Lett., 1989, 1481; (b) R. D. Bereman, J. R. Dorfman, J. Bordner, D. P. Rillema, P. McCarthy and G. D. Shields, J. Bioinorg. Chem., 1982, 16, 47; (c) M. Culotti, L. Casella, A. Pintar, E. Suardi, P. Zanello and S. Mangani, J. Chem. Soc., Dalton Trans., 1989, 1979.
18. F. Woldby, Studies of Optical Activity, Polyteknisk Forlag, Copenhagen, 1973, pp. 134, 180(in Danish); F. H. Dickey, W. Ficket and H. J. Lucas, J. Am. Chem. Soc., 1952, 74, 944.
19. C. Harries and T. Haga, Ber. Dtsch. Chem. Ges., 1898, 31, 550; 1899, 32, 1191.
20. J. Becher, K. Pluta, N. Krake, K. Brøndum, N. J. Christensen and M. V. Vinader, Synthesis, 1985, 530; J. Becher, P. L. Jørgensen, H. Frydendahl and B. Fält Hansen, Synthesis, 1991, 609.
21. (a) G. M. Sheldrick, SHELXTL, version 5, Siemens Analytical X-Ray Division, Madison, WI, 1994; (b) M. S. Lehmann and F. K. Larsen, Acta Crystallogr., Sect. A, 1974, 30, 580; (c) G. M. Sheldrick, SHELXS 86, Program for the Solution of Crystal Structures, University of Göttingen, 1986; (d) W. T. Busing, K. O. Martin and H. A. Levy, ORFLS, Report ORNL-TM-306, Oak Ridge National Laboratory, Oak Ridge, TN, 1962; (e) G. S. Pawley, in Advances in Structure Research by Diffraction Methods, eds. W. Hoppe and R. Mason, Pergamon, Oxford, 1971, vol. 4, pp. 1–64; (f) V. Schomaker and K. N. Trueblood, Acta Crystallogr., Sect. B, 1968, 24, 63; (g) International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. 4, pp. 72–98; (h) SADABS, a program for Siemens area detector absorption corrections, G. M. Sheldrick, unpublished work.