The structure of diphosphaallenic radical cations as evidenced by EPR experiments and ab initio calculations

Abstract

The isotropic hyperfine coupling constants of the diphosphaalkene radical cation have been measured by EPR spectroscopy after electrochemical oxidation of ArP=C=PAr (and ArP=¹³C=PAr) in tetrahydrofuran (THF). The two ³¹P constants as well as the ¹³C coupling are close to 90 MHz. Taking HPCPH as a model compound, the structure has been assessed, by extensive ab initio calculations including correlation effects at the MP2 and MCSCF levels of theory. It is found that oxidation of the allenic –P=C=P– structure leads to the formation of two rotamers with HPPH dihedral angles of 45° and 135°. These two structures are compatible with the Jahn–Teller distortion of allene. The calculated hyperfine constants support the EPR results.

References

1. R. J. Brudzinski and B. S. Hudson, J. Am. Chem. Soc., 1990, 112, 4963.
2. N. Koga and K. Morokuma, J. Am. Chem. Soc., 1991, 113, 1907.
3. E. Haselbach, Chem. Phys. Lett., 1970, 7, 428.
4. Y. Takemura and T. Shida, J. Chem. Phys., 1980, 73, 4133.
5. K. Haddaway, K. Somekawa, P. Fleming, J. A. Tossell and P. S. Mariano, J. Org. Chem., 1987, 52, 4239.
6. K. Lammertsma and P. v. R. Schleyer, J. Am. Chem. Soc., 1990, 112, 7935.
7. M. W. Wong and L. Radom, J. Mol. Struct., 1989, 198, 391.
8. R. Furet, R. L. Matcha and R. Fuchs, J. Phys. Chem., 1986, 90, 5571.
9. N. J. Fitzpatrick, D. F. Brougham, P. J. Goarke and M. T. Nguyen, Chem. Ber., 1994, 127, 969.
10. K. Toyota, M. Shibata and M. Yoshifuji, Bull. Chem. Soc. Jpn., 1995, 68, 2633.
11. Multiple Bonds and Low Coordination in Phosphorus Chemistry, eds. M. Regitz and O. Scherer, Thieme, New York, 1990.
12. (a) W. W. Schoeller, J. Niemann and R. Thiele, Chem. Ber., 1991, 124, 417; (b) M. Geoffroy, A. Jouaiti, G. Terron, M. Cattani-Lorente and Y. Ellinger, J. Phys. Chem., 1992, 96, 8241; (c) A. Jouaiti, M. Geoffroy, G. Terron and G. Bernardinelli, J. Am. Chem. Soc., 1995, 117, 2251; (d) W. W. Schoeller, W. Haug, J. Strutwolf and T. Busch, J. Chem. Soc., Faraday Trans., 1996, 92, 1751.
13. H. H. Karsh, H.-U. Reisacher and G. Müller, Angew. Chem., Int. Ed. Engl., 1994, 23, 618.
14. M. T. Nguyen and A. F. Hegarty, J. Chem. Soc., Perkin Trans. 2, 1985, 2005.
15. G. Frenking and H. Schwarz, Z. Naturforsch., Teil B, 1982, 37, 1602.
16. M. W. Wong and C. Wentrup, J. Am. Chem. Soc., 1993, 115, 7743.
17. H. H. Karsch, F. H. Köhler and H.-U. Reisacher, Tetrahedron Lett., 1984, 25, 3687.
18. M. Yoshifuji, J. Chem. Soc., Chem. Commun., 1984, 689.
19. L. Krieger, Ph.D. Dissertation, University of Bonn, Germany, 1988.
20. GAUSSIAN92, M. J. Frisch, G. W. Trucks, M. Head-Gordon, P. M. W. Gill, M. W. Wong, J. B. Foresman, B. G. Johnson, H. B. Schlegel, M. A. Robb, E. S. Replogle, R. Gomperts, J. L. Anders, K. Raghavachari, J. S. Binkley, C. Gonzalez, R. L. Martin, D. J. Fox, D. J. DeFrees, J. Baker, J. J. P. Stewart and J. A. Pople, Gaussian, Inc., Pittsburgh, PA, USA.
21. HONDO 8.5 from CHEM-Station, M. Dupuis, F. Jonhston and A. Marquez, 1994, IBM Corporation, Neighborhood Road, Kingston, NY 12401, USA.
22. P. Flukiger, Development of Molecular Graphics Package MOLEKEL and its Applications to Selected Problems in Organic and Organometallic Chemistry. Ph.D. Thesis No. 2561. University of Geneva, Switzerland, 1992.
23. J. R. Morton and K. F. Preston, J. Magn. Reson., 1978, 30, 577.
24. G. Ramakrishnan, A. Jouaiti, M. Geoffroy and G. Bernardinelli, J. Phys. Chem., 1996, 100, 10 861.
25. (a) T. Cole and C. Heller, J. Chem. Phys., 1961, 34, 1085; (b) H. M. McConnell, C. Heller, T. Cole and R. W. Fessenden, J. Am. Chem. Soc., 1960, 82, 766.
26. R. Bolze, H. Eierdanz, K. Schlüter, W. Massa, W. Grahn and A. Berndt, Angew. Chem., Int. Ed. Engl., 1982, 21, 924.
27. D. Feller, E. Huyser, W. T. Borden and E. R. Davidson, J. Am. Chem. Soc., 1983, 105, 1459.
28. (a) O. Parisel, M. Hanus and Y. Ellinger, J. Phys. Chem., 1996, 100, 2926; (b) O. Parisel, M. Hanus and Y. Ellinger, J. Chem. Phys., 1996, 104, 1979.
29. A. P. Scott and L. Radom, J. Phys. Chem., 1996, 100, 16 502.
30. (a) D. J. DeFrees, M. P. Miller, D. Talbi and Y. Ellinger, Astrophys. J., 1993, 408, 530; (b) S. R. Langhoff, J. Phys. Chem., 1996, 100, 2819.
31. (a) W. H. Miller, N. C. Handy and J. E. Adams, J. Chem. Phys., 1985, 82, 1281; (b) V. Barone, A. Grand, C. Minichino and R. Subra, in Strategies and Applications in Quantum Chemistry, eds. Y. Ellinger and M. Defranceschi, Kluwer, Dordrecht, 1996, p. 251.