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DOI: 10.1039/A705048H (Paper) Reference Section for: J. Chem. Soc., Dalton Trans., 1997, 4733-4738

Acetonitrile and propionitrile exchange at palladium(II) and platinum(II)[hair space]†

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Ola F. Wendt, Nils-Fredrik K. Kaiser and Lars I. Elding

Abstract

Ligand exchange at square-planar [Pd(MeCN)4]2+ and [Pd(EtCN)4]2+ has been studied by 1H NMR line broadening and at [Pt(MeCN)4]2+ and [Pt(EtCN)4]2+ by isotopic labelling using 1H NMR spectroscopy in deuteriated nitromethane. Exchange takes place via two-term rate laws Rex/4 = (k1 + k2[RCN])cM with well defined k1 paths. Rate constants per co-ordination site k1298/s–1, k2298/kg mol–1 s–1 are 6.9 ± 1.6, 34 ± 3; 0.59 ± 0.12, 34 ± 3; 10.7 ± 1.8, 35 ± 4; (5.1 ± 2.3) × 10–6, (2.8 ± 0.2) × 10–5 and (5.5 ± 1.0) × 10–6, (3.3 ± 0.2) × 10–5 for [Pd(MeCN)4][CF3SO3]2, [Pd(MeCN)4][BF4]2, [Pd(EtCN)4][CF3SO3]2, [Pt(MeCN)4][CF3SO3]2 and [Pt(EtCN)4][CF3SO3]2, respectively. For [Pd(MeCN)4]2+ the k1 path is much larger for triflate than for tetrafluoroborate as counter ion. Changing the tetrafluoroborate concentration has no effect on the exchange rate of acetonitrile at [Pd(MeCN)4]2+. In this case the k1 path is ascribed to an attack by solvent at the metal centre. For triflate saturation kinetics is observed. This can be rationalized in terms of ion-pair formation followed by reversible intramolecular exchange of nitrile for triflate within the ion pair, with an equilibrium constant Kip300 = 8 ± 2 kg mol–1 and a rate constant k300 = 12.5 ± 1.3 s–1. All activation entropies are negative, indicating associative activation. A new, simple one-step synthesis of the substrate complexes as their triflate salts, using [M(acac)2] (acac = acetylacetonate) as starting material, and of [Pd(MeCN)4][BF4]2 using palladium(II) acetate, is described.

References

  1. Ö. Gröning, T. Drakenberg and L. I. Elding, Inorg. Chem., 1982, 21, 1820 CrossRef CAS.
  2. J. J. Pesek and W. R. Mason, Inorg. Chem., 1983, 22, 2958 CrossRef CAS.
  3. L. Helm, L. I. Elding and A. E. Merbach, Helv. Chim. Acta, 1984, 67, 1453 CrossRef CAS.
  4. L. Helm, L. I. Elding and A. E. Merbach, Inorg. Chem., 1985, 24, 1719 CrossRef CAS.
  5. Y. Ducommun, L. Helm, A. E. Merbach, B. Hellquist and L. I. Elding, Inorg. Chem., 1989, 28, 377 CrossRef CAS.
  6. B. Brønnum, H. S. Johansen and L. H. Skibsted, Acta Chem. Scand., 1989, 43, 975.
  7. U. Frey, S. Elmroth, B. Moullet, L. I. Elding and A. E. Merbach, Inorg. Chem., 1991, 30, 5033 CrossRef CAS.
  8. N. Hallinan, V. Besançon, M. Forster, G. Elbaze, Y. Ducommun and A. E. Merbach, Inorg. Chem., 1991, 30, 1112 CrossRef CAS.
  9. V. Y. Kukushkin, Å. Oskarsson and L. I. Elding, Inorg. Synth., 1996, 31, 279.
  10. G. Alibrandi, R. Romeo, L. M. Scolaro and M. L. Tobe, Inorg. Chem., 1992, 31, 5061 CrossRef CAS.
  11. T. Yagyu, S. Aizawa, K. Hatano and S. Funahashi, Bull. Chem. Soc. Jpn., 1996, 69, 1961 CAS.
  12. B. Heyn, B. Hipler, G. Kreisel, H. Schreer and D. Walther, Anorganische Synthesechemie, Springer, Berlin, 1986, p.129 Search PubMed.
  13. S. Okeya and S. Kawaguchi, Inorg. Synth., 1980, 20, 65.
  14. H. Kobler, R. Munz, G. Al Gasser and G. Simchen, Liebigs Ann. Chem., 1978, 1937 Search PubMed.
  15. R. R. Thomas and A. Sen, Inorg. Synth., 1990, 28, 63 CAS.
  16. H. Kobler, K.-H. Schuster and G. Simchen, Liebigs Ann. Chem., 1978, 1946 Search PubMed.
  17. D. S. Stephenson and G. Binsch, QCPE, 1978, 11, 365 Search PubMed.
  18. R. M. Fuoss, J. Am. Chem. Soc., 1958, 80, 5059 CrossRef CAS.
  19. J. H. Espenson, Chemical Kinetics and Reaction Mechanisms, McGraw-Hill, New York, 2nd edn., 1995, p. 56.
  20. R. G. Pearson, H. B. Gray and F. Basolo, J. Am. Chem. Soc., 1960, 82, 787 CAS.
  21. O. P. Anderson and A. B. Packard, Inorg. Chem., 1979, 18, 1129 CrossRef CAS.
  22. P. Svensson, K. Lövquist, V. Y. Kukushkin and Å. Oskarsson, Acta Chem. Scand., 1995, 49, 72 CrossRef CAS.
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