Experimental investigation of the bonding characteristics and charge distribution of a nitrogen ylide by high resolution X-ray diffraction

Abstract

The experimental charge density of trimethylammonionitramidate, (CH₃)₃N⁺–N^- –NO₂, has been determined by high resolution X-ray diffraction. We find the distribution of charge to be more complex than the Lewis formula suggests. Despite the fact that the trimethylammonium fragment bears a full positive charge, the ’onium nitrogen is determined to have a substantial negative charge due to electron donation from the methyl groups by the alkyl inductive effect. The formally negative nitrogen atom of the N⁺–N^- bond has its charge substantially reduced by the electron-withdrawing nitro group considerably stabilising the molecule. The topological properties of the -∇²ρ(r) distribution for this nitrogen atom suggest it to be sp² hybridised.

References

1. D. A. Dixon, T. H. Dunning Jr., R. A. Eades and P. G. Gassman, J. Am. Chem. Soc., 1983, 105, 7014.
2. T. Naito, S. Nagase and H. Yamataka, J. Am. Chem. Soc., 1994, 116, 10 080.
3. A. E. Reed, R. B. Weinstock and F. Weinhold, J. Chem. Phys., 1985, 83, 735.
4. A. E. Reed, L. A. Curtiss and F. Weinhold, Chem. Rev., 1988, 88, 899.
5. A. F. Cameron, N. J. Hair and D. G. Morris, J. Chem. Soc., Perkin Trans. 2, 1972, 1071.
6. S. Tsuchiya and M. Senō, J. Phys. Chem., 1994, 98, 13 680.
7. S. Inubushi, T. Ikeda and S. Tazuke, J. Polym. Sci., A, 1987, 25, 137.
8. J. Jazwinski, W. Kozminski, L. Stefaniak and G. A. Webb, J. Mol. Struct., 1991, 243, 365.
9. S. Tsuchiya and M. Senō, J. Org. Chem., 1979, 44, 2850.
10. S. Tsuchiya and M. Senō, J. Chem. Soc., Perkin Trans. 2, 1983, 887.
11. J. Epsztajn and A. R. Katritzky, Tetrahedron Lett., 1969, 54, 4739.
12. S. T. Howard, M. B. Hursthouse, C. W. Lehmann, P. R. Mallinson and C. S. Frampton, J. Chem. Phys., 1992, 97, 5616.
13. R. H. Blessing, J. Appl. Crystallogr., 1989, 22, 396 and references cited therein.
14. G. DeTitta, Program ABSORB, Medical Foundation of Buffalo, USA, 1994.
15. T. Koritsanszky, S. T. Howard, P. R. Mallinson, Z. Su, T. Richter and N. K. Hansen, XD; a computer program package for multipole refinement and analysis of charge densities from diffraction data, 1995.
16. R. F. Stewart, Acta Crystallogr., Sect. A, 1976, 32, 565.
17. E. Clementi and C. Roetti, Atomic Data and Nuclear Data Tables, 1974, 14, 177.
18. N. K. Hansen and P. Coppens, Acta Crystallogr., Sect. A, 1978, 34, 909.
19. K. Kurki-Suonio, Israel J. Chem., 1977, 16, 115.
20. R. F. Stewart, E. R. Davidson and W. T. Simpson, J. Chem. Phys., 1965, 42, 3175.
21. F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and R. Taylor, J. Chem. Soc., Perkin Trans. 2, 1987, S1.
22. F. L. Hirshfeld, Acta Crystallogr., Sect. A, 1976, 32, 239.
23. R. F. W. Bader, Atoms in Molecules: A Quantum Theory, Oxford University Press, Oxford, 1990.