Metal-mediated couplings of a diphosphastibolyl ring anion, [1,4,2-P₂SbC₂Bu^t₂]^–: synthesis and characterisation of novel antimony-containing cage compounds

Abstract

Two equivalents of the diphosphastibolyl ring anion, [1,4,2-P₂SbC₂Bu^t₂]^– reacted with FeCl₃ to produce an antimony-containing cage compound, P₄Sb₂C₄Bu^t₄, via an oxidative coupling mechanism. This cage underwent an intramolecular rearrangement reaction when treated with [W(CO)₅(thf )] (thf = tetrahydrofuran) to produce the complex [{W(CO)₅}P₄Sb₂C₄Bu^t₄], which X-ray crystallography shows to contain a three-membered PPC ‘diphosphirane’ ring. Treatment of cis-[PtCl₂(PEt₃)₂] with 1 equivalent of [1,4,2-P₂SbC₂Bu^t₂]^– yielded the first example of a complex, trans-[PtCl(PEt₃)₂(η¹-P₂SbC₂Bu^t₂)], containing a solely η¹-co-ordinated diphosphastibolyl ring. The crystal structure of this compound shows the heterocyclic ring to retain its aromaticity after co-ordination. Treatment of cis-[PtCl₂(PEt₃)₂] with 2 equivalents of [1,4,2-P₂SbC₂Bu^t₂]^– initiated a ring-coupling reaction at the metal to give the novel cage complex cis-[Pt(PEt₃)₂(η²-P₄Sb₂C₄Bu^t₄]. The molecular structure of the cage shows it to contain a highly strained, dianionic ligand, [P₄Sb₂C₄Bu^t₄]^2–, which chelates the platinum through antimony and phosphorus atoms. Unusual features in the ³¹P-{¹H} NMR spectrum of the complex are described.

References

1. R. Streubel, Angew. Chem., Int. Ed. Engl., 1995, 34, 436 and refs. therein A. Mack and M. Regitz, Chem. Ber., 1997, 130, 823 and refs. therein.
2. T. Wettling, J. Schneider, O. Wagner, C. G. Kreiter and M. Regitz, Angew. Chem., Int. Ed. Engl., 1989, 28, 1013.
3. F. Mathey, Coord. Chem. Rev., 1994, 137, 1 and refs. therein.
4. R. Bartsch, P. B. Hitchcock and J. F. Nixon, J. Organomet. Chem., 1989, 375, C31.
5. P. B. Hitchcock, J. A. Johnson and J. F. Nixon, Angew. Chem., Int. Ed. Engl., 1993, 32, 103.
6. M. D. Francis, D. E. Hibbs, M. B. Hursthouse, C. Jones and K. M. A. Malik, J. Organomet. Chem., 1997, 527, 291.
7. S. J. Black and C. Jones, J. Organomet. Chem., 1997, 534, 89.
8. S. J. Black, M. D. Francis and C. Jones, J. Chem. Soc., Dalton Trans., 1997, 2183.
9. S. J. Black, M. D. Francis and C. Jones, Chem. Commun., 1997, 305.
10. P. B. Hitchcock, C. Jones and J. F. Nixon, J. Chem. Soc., Chem. Commun., 1995, 2167.
11. R. Bartsch, D. Carmichael, P. B. Hitchcock, M. F. Meidine, J. F. Nixon and G. J. D. Sillett, J. Chem. Soc., Chem. Commun., 1988, 1615.
12. P. B. Hitchcock, J. F. Nixon and G. J. D. Sillett, New J. Chem., 1989, 13, 353.
13. J. F. Nixon and A. Pidcock, Ann. Rep. N.M.R. Spectrosc., 1969, 2, 345.
14. W. Kemp, NMR in Chemistry, Macmillan, London, 3rd edn., 1992, p. 63.
15. F. W. Heinemann, M. Gerisch, K. Schnezel and D. Steinborn, Z. Kristallogr., 1996, 211, 388.
16. G. W. Parshall, Inorg. Synth., 1970, 12, 27.
17. J. A. Darr, S. A. Drake, M. B. Hursthouse and K. M. A. Malik, Inorg. Chem., 1993, 32, 5704.
18. G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467.
19. G. M. Sheldrick, SHELXL 93, Program for Crystal Structure Refinement, University of Göttingen, 1993.
20. International Tables for X-Ray Crystallography, eds. J. A. Ibers and W. C. Hamilton, Kynoch Press, Birmingham, 1974, vol. 4.
21. N. P. C. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983, 39, 158; adapted for FAST geometry by A. I. Karavlov, University of Wales, Cardiff, 1991.