Thermal C–P and C–H cleavage in co-ordinated phosphines leading to dinuclear platinum complexes and contrasting reactions with M(PPh₃)⁺ (M = Cu, Ag or Au) and HgCl₂†

Abstract

The dinuclear complex [Pt₂(µ-PPh₂){µ-(o-C₆H₄PPh₂)}(PPh₃)₂] was prepared by controlled thermolysis of [Pt(C₂H₄)(PPh₃)₂] and it contains both a diphenylphosphido and an ortho-metallated triphenylphosphine ligand that bridge the Pt^I–Pt^I bond [2.657(1) Å in 3 and 2.677(5) Å in the CH₂Cl₂ adduct]. Addition of the electrophilic metal reagents [M(PPh₃)]⁺ (M = Cu, Ag or Au) occurs at the Pt–Pt bond, affording [Pt₂{µ-M(PPh₃)}(µ-PPh₂){µ-(o-C₆H₄PPh₂)}(PPh₃)₂]⁺ (M = Cu, Ag or Au) whereas selective oxidation by HgCl₂ gives the dinuclear platinum(II) complex [Pt₂Cl₂(µ-PPh₂){µ-(o-C₆H₄PPh₂)}(PPh₃)₂] which is shown to have a “mixed-geometry” structure at the metal centres (square planar and flattened tetrahedral). The new complexes have been analysed by ³¹P-{¹H} and ¹⁹⁵Pt NMR spectroscopy and the structures of three complexes have been determined by X-ray diffraction.

References

1. L. Malatesta and M. Angoletta, J. Chem. Soc., 1957, 1186; L. Malatesta and C. Cariello, J. Chem. Soc., 1958, 2323.
2. P. E. Garrou, Chem. Rev., 1985, 85, 171.
3. N. J. Taylor, P. C. Chieh and A. J. Carty, J. Chem. Soc., Chem. Commun., 1975, 448.
4. R. Bender, P. Braunstein, A. Tiripicchio and M. Tiripicchio Camellini, Angew. Chem., Int. Ed. Engl., 1985, 24, 861.
5. R. Bender, P. Braunstein, A. Dedieu, P. D. Ellis, B. Higgins, P. D. Harvey, E. Sappa and A. Tiripicchio, Inorg. Chem., 1996, 35, 1223.
6. O. J. Scherer and K. Hussong, personal communication.
7. R. Bender, C. Archambault and P. Braunstein, Xth FECHEM Conference on Organometallic Chemistry, Agia Pelagia, Crete (Greece), 5–10 September, 1993, Abstract P45.
8. C. Archambault, R. Bender, P. Braunstein, A. DeCian and J. Fischer, Chem. Commun., 1996, 2729.
9. M. A. Bennett, D. E. Berry, S. K. Bhargava, E. J. Ditzel, G. B. Robertson and A. C. Willis, J. Chem. Soc., Chem. Commun., 1987, 1613.
10. D. M. Blake and C. J. Nyman, Chem. Commun., 1969, 483 Note however that in their full paper these authors did not confirm the presence of a cyclometallated ligand: D. M. Blake and C. J. Nyman, J. Am. Chem. Soc., 1970, 92, 5359.
11. F. Glockling, T. McBride and R. J. I. Pollock, J. Chem. Soc., Chem. Commun., 1973, 650.
12. S. Sostero, O. Traverso, M. Lenarda and M. Graziani, J. Organomet. Chem., 1977, 134, 259.
13. H. C. Clark and K. E. Hine, J. Organomet. Chem., 1976, 105, C32.
14. D. P. Arnold, M. A. Bennett, M. S. Bilton and G. B. Robertson, J. Chem. Soc., Chem. Commun., 1982, 115.
15. M. A. Bennett, D. E. Berry, T. Dirnberger, D. C. R. Hockless and E. Wenger, J. Chem. Soc., Dalton Trans., 1998, 2367.
16. R. Bender and P. Braunstein, unpublished results.
17. Phosphorus-31 NMR Spectroscopy in Stereochemical Analysis, VCH, Weinheim, 1987, p. 559.
18. R. Bender, P. Braunstein, A. Dedieu and Y. Dusausoy, Angew. Chem., Int. Ed. Engl., 1989, 28, 923.
19. P. R. Sharp, Inorg. Chem., 1986, 25, 4185.
20. P. Braunstein, M. Ries, C. de Méric de Bellefon, Y. Dusausoy and J.-P. Mangeot, J. Organomet. Chem., 1988, 355, 533.
21. M. A. Bennett, S. K. Bhargava, D. C. Hockless, L. L. Welling and A. C. Willis, J. Am. Chem. Soc., 1996, 118, 10469.
22. U. Nagel, Chem. Ber., 1982, 115, 1998.
23. SDP Structure Determination Package, Enraf-Nonius, Delft, 1977.
24. G. M. Sheldrick, Programs for Crystal Structure Determination, University of Göttingen, 1976.
25. N. Walker and D. Stuart, Acta Crystallogr., Sect. A, 1983, 39, 159.
26. International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. IV.