View PDF Version
 
DOI: 10.1039/A809451I (Paper) Reference Section for: J. Chem. Soc., Dalton Trans., 1999, 691-698

Oxidatively induced isomerisation of vinylidene ligands to alkynes: ESR spectra of paramagnetic vinylidene and alkyne arene metal complexes

(Note: The full text of this document is currently only available in the PDF Version )

Ian M. Bartlett, Neil G. Connelly, Antonio J. Martín, A. Guy Orpen, Timothy J. Paget, Anne L. Rieger and Philip H. Rieger

Abstract

UV irradiation of [M(CO)3(η-arene)] and Me3SiC[triple bond, length half m-dash]CSiMe3 gives [M(CO)2{C[double bond, length half m-dash]C(SiMe3)2}(η-arene)] (M = Cr, arene = C6H2Me4-1,2,3,5 2V, C6H3Me3-1,2,3 3V or C6H6 4V; M = Mo, arene = C6Me6 5V or C6H3Me3-1,3,5 6V). The crystal structure of [Cr(CO)2{C[double bond, length half m-dash]C(SiMe3)2}(η-C6H6)] 4V confirms the presence of the vinylidene ligand; the complex has approximate Cs symmetry with the C(SiMe3)2 plane orthogonal to the arenecentroid–Cr–Cα–Cβ plane. Voltammetry and IR and NMR spectroscopy show that in solution [Mo(CO)2{C[double bond, length half m-dash]C(SiMe3)2}(η-C6H3Me3-1,3,5)] 6V thermally equilibrates with the alkyne isomer [Mo(CO)2(η-Me3SiC[triple bond, length half m-dash]CSiMe3)(η-C6H3Me3-1,3,5)] 6A. The vinylidene complexes [M(CO)2{C[double bond, length half m-dash]C(SiMe3)2}(η-arene)] 2V–6V undergo one-electron oxidation to the alkyne cations [M(CO)2(η-Me3SiC[triple bond, length half m-dash]CSiMe3)(η-arene)]+ 2A+–6A+via fast, redox-induced vinylidene-to-alkyne isomerisation. These cations are reduced to the neutral alkyne complexes [M(CO)2(η-Me3SiC[triple bond, length half m-dash]CSiMe3)(η-arene)] 2A–6A which slowly isomerise thermally to the neutral vinylidene complexes 2V–6V. Paramagnetic vinylidene and alkyne complex cations have been characterised by ESR spectroscopy; unpaired electron density is extensively delocalised from the metal centre to the C2 ligand, in agreement with the results of EHMO calculations.

References

  1. N. G. Connelly, W. E. Geiger, M. C. Lagunas, B. Metz, A. L. Rieger, P. H. Rieger and M. J. Shaw, J. Am. Chem. Soc., 1995, 117, 12202 CrossRef CAS.
  2. N. G. Connelly, A. G. Orpen, A. L. Rieger, P. H. Rieger, C. J. Scott and G. M. Rosair, J. Chem. Soc., Chem. Commun., 1992, 1293 RSC.
  3. N. G. Connelly and G. A. Johnson, J. Organomet. Chem., 1974, 77, 341 CrossRef CAS.
  4. I. M. Bartlett, N. G. Connelly, A. G. Orpen, M. J. Quayle and J. C. Rankin, Chem. Commun., 1996, 2583 RSC.
  5. R. Davis and L. A. P. Kane-Maguire, in Comprehensive Organo-metallic Chemistry, eds. G. W. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon Press, Oxford, 1982, vol. 3, 1035 Search PubMed.
  6. R. Davis and L. A. P. Kane-Maguire, in Comprehensive Organometallic Chemistry, eds. G. W. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon Press, Oxford, 1982, vol. 3, 1218 Search PubMed.
  7. M. I. Bruce, Chem. Rev., 1991, 91, 197 CrossRef CAS.
  8. M. I. Bruce and A. G. Swincer, Adv. Organomet. Chem., 1983, 22, 59 CAS.
  9. A. B. Antonova, N. E. Kolobova, P. V. Petrovsky, B. V. Lokshin and N. S. Obezyuk, J. Organomet. Chem., 1977, 137, 55 CrossRef CAS.
  10. U. Schubert and J. Grönen, Chem. Ber., 1989, 122, 1237 CAS; U. Schubert, U. Kirchgässner, J. Grönen and H. Piana, Polyhedron, 1989, 8, 1589 CrossRef CAS.
  11. P. D. Magnus, T. Sarkar and S. Djuric, in Comprehensive Organometallic Chemistry, eds. G. W. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon Press, Oxford, 1982, vol. 7, 515 Search PubMed.
  12. B. Rees and P. Coppens, Acta Crystallogr., Sect. B, 1973, 29, 2516 CrossRef CAS.
  13. H. Berke, G. Huttner and J. von Seyerl, J. Organomet. Chem., 1981, 218, 193 CrossRef CAS.
  14. J. Silvestre and R. Hoffmann, Helv. Chim. Acta, 1985, 68, 1461 CrossRef CAS.
  15. N. M. Kostic and R. F. Fenske, Organometallics, 1982, 1, 974 CrossRef CAS.
  16. K. R. Birdwhistell, T. L. Tonker and J. L. Templeton, J. Am. Chem. Soc., 1987, 109, 1401 CrossRef CAS.
  17. R. M. Bullock, J. Chem. Soc., Chem. Commun., 1989, 165 RSC.
  18. J. J. Kowalczyk, A. M. Arif and J. A. Gladysz, Organometallics, 1991, 10, 1079 CrossRef CAS.
  19. R. Prins and F. J. Reinders, Chem. Phys. Lett., 1969, 3, 45 CrossRef CAS.
  20. K. H. Hausser, Naturwissenshaften, 1961, 48, 426 CAS.
  21. E. Keules and F. Jellinek, J. Organomet. Chem., 1966, 5, 490 CrossRef CAS.
  22. S. Alvarez, Tables of Parameters for Extended Huckel Calculations, University of Barcelona, Barcelona, 1989 Search PubMed.
  23. E. L. Muetterties, J. R. Bleeke, E. J. Wucherer and T. A. Albright, Chem. Rev., 1982, 82, 499 CrossRef CAS.
  24. A. D. Krivospitskii and G. K. Chirkin, Zh. Strukt. Khim., 1974, 15, 25 Search PubMed.
  25. S. E. Anderson, Jr. and R. S. Drago, Inorg Chem., 1972, 11, 1564 CrossRef CAS.
  26. W. Karthe and W. Kleinwächter, Ann. Phys. (Leipzig), 1968, 21, 137 Search PubMed; B. G. Gribov, B. I. Kozyrkin, A. D. Krivospitskii and G. K. Chirkin, Dokl. Akad. Nauk SSSR, 1970, 193, 91 Search PubMed.
  27. R. Wilson and D. Kivelson, J. Chem. Phys., 1966, 44, 4445 CAS.
  28. J. R. Morton and K. F. Preston, J. Magn. Reson., 1978, 30, 577 CAS.
  29. B. Nicholls and M. C. Whiting, J. Chem. Soc., 1959, 551 RSC.
  30. A. Pidcock, J. D. Smith and B. W. Taylor, J. Chem. Soc. A, 1967, 872 RSC.
  31. N. G. Connelly and W. E. Geiger, Chem. Rev, 1996, 96, 877 CrossRef CAS; J. C. Smart and B. L. Pinsky, J. Am. Chem. Soc., 1980, 102, 1009 CrossRef CAS.
  32. N. C. Brown, G. B. Carpenter, N. G. Connelly, J. G. Crossley, A. Martin, A. G. Orpen, A. L. Rieger, P. H. Rieger and G. H. Worth, J. Chem. Soc., Dalton Trans., 1996, 3977 RSC.
Click here to see how this site uses Cookies. View our privacy policy here.