C–H · · · C Hydrogen bonding involving ylides

Abstract

Ab initio calculations on nitrogen and phosphorous ylides, and their complexes with methane and acetylene, are reported. A hydrogen bond strength of 35 kJ mol^–1 is found between H₃N–CH₂ and acetylene at the MP2/6-311++G(3d,3p) level; even with methane as the proton donor some stabilisation (ca. 5 kJ mol^–1) is predicted. Complexes of H₃P–CH₂ are found to be rather less stable (19 kJ mol^–1 with acetylene). Topological analysis of the charge density indicates a fundamental difference in the bonding between H₃N–CH₂ and H₃P–CH₂, with significant double bond character only in the latter. Atoms in molecules decomposition identifies the source of the hydrogen bond strength to be stabilisation of C in the N ylides and stabilisation of P in the P ylides. The effects of methyl and phenyl substituents on the ylidic carbon are investigated: methyl substitution enhances basicity slightly, but phenyl substitution decreases it dramatically. There is some suggestion that this may be a steric as well as an electronic effect.

References

1. J. A. Platts, S. T. Howard and K. Wol̄niak, J. Chem. Soc., Commun., 1996, 63.
2. G. R. Desiraju, Acc. Chem. Res., 1991, 24, 290.
3. A. S. Batsanov, M. G. Davidson, J. A. K. Howard, S. Lamb and C. Lustig, J. Chem. Soc., Chem. Commun., 1996, 1791.
4. See, for example: (a) D. S. Dudis, J. B. Everhart, T. M. Branch and S. S. Hunnicut, J. Phys. Chem., 1996, 100, 2083; (b) G. B. Backsay, Mol. Phys., 1992, 77, 61; (c) J. S. Craw and G. B. Backsay, J. Chem. Soc., Faraday Trans., 1992, 88, 2315; (d) M. J. Frisch, J. A. Pople and J. E. Del Bene, J. Phys. Chem., 1985, 89, 3664.
5. P. G. Sennikov, J. Phys. Chem., 1994, 98, 6487 and references cited therein.
6. (a) J. J. Novoa, B. Tarron, M. H. Whangbo and J. M. Williams, J. Chem. Phys., 1991, 95, 5179; (b) I. Alkorta and S. Maluendes, J. Phys. Chem., 1995, 99, 6457.
7. A. W. Johnson(with special contributions by W. C. Kaska, K. A. O. Starewski and D. A. Dixon), Ylides and Imines of Phosphorous, Wiley, New York, 1993.
8. (a) C. Moller and M. S. Plesset, Phys. Rev., 1934, 46, 618; (b) J. A. Pople, J. S. Binkley and R. Seeger, Int. J. Quantum Chem., Quantum Chem. Symp., 1976, 10, 1.
9. (a) R. Krishnan, J. S. Binkley and J. A. Pople, J. Chem. Phys., 1980, 72, 650; (b) P. C. Hariharan and J. A. Pople, Theor. Chim. Acta, 1973, 28, 213; (c) M. J. Frisch, J. A. Pople and J. S. Binkley, J. Chem. Phys., 1984, 80, 3265.
10. GAUSSIAN94 Rev. C3, M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson, J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian, Inc., Pittsburgh PA, 1995.
11. S. F. Boys and F. Bernardi, Mol. Phys., 1970, 19, 553.
12. (a) W. J. Hehre, R. Ditchfield and J. A. Pople, J. Chem. Phys., 1972, 56, 2257; (b) R. Ditchfield, W. J. Hehre and J. A. Pople, J. Chem. Phys., 1971, 54, 724.
13. (a) R. F. W. Bader, Atoms in Molecules: A Quantum Theory, OUP, New York, 1994; (b) R. F. W. Bader, Chem. Rev., 1991, 91, 893; (c) R. F. W. Bader, Acc. Chem. Res., 1985, 18, 9.
14. R. F. W. Bader and H. Essen, J. Chem. Phys., 1984, 80, 1943.
15. R. F. W. Bader, P. J. MacDougall and C. D. H. Lau, J. Am. Chem. Soc., 1984, 106, 1594.
16. (a) R. F. W. Bader and C. Chang, J. Phys. Chem., 1989, 93, 2946; (b) M. T. Carroll, J. R. Cheeseman, R. Osman and H. Weinstein, J. Phys. Chem., 1989, 93, 5120.
17. F. W. Biegler-König, R. F. W. Bader and T.-H. Tang, J. Comput. Chem., 1982, 3, 317.
18. R. F. W. Bader, J. Chem. Phys., 1980, 73, 2871.
19. (a) R. F. W. Bader, J. R. Cheeseman, K. E. Laidig, K. B. Wiberg and C. Breneman, J. Am. Chem. Soc., 1990, 112, 6530; (b) R. F. W. Bader and P. F. Zou, Chem. Phys. Lett., 1992, 191, 54; (c) R. Glaser and G. S.-C. Choy, J. Am. Chem. Soc., 1993, 115, 2340.
20. (a) M. T. Carroll and R. F. W. Bader, Mol. Phys., 1988, 65, 695; (b) P. L. A. Popelier and R. F. W. Bader, Chem. Phys. Lett., 1992, 189, 542; (c) U. Koch and P. L. A. Popelier, J. Phys. Chem., 1995, 99, 9747; (d) J. A. Platts, S. T. Howard and B. R. F. Bracke, J. Am. Chem. Soc., 1996, 118, 2726.
21. R. F. W. Bader and C. Chang, J. Phys. Chem., 1989, 93, 5095.
22. R. F. W. Bader, M. T. Carroll, J. R. Cheeseman and C. Chang, J. Am Chem. Soc., 1989, 109, 7968.
23. (a) R. F. W. Bader, A. Larouche, C. Gatti, M. T. Carroll, P. J. MacDougall and K. B. Wiberg, J. Chem. Phys., 1987, 87, 1142; (b) K. E. Laidig, Chem. Phys. Lett., 1994, 225, 285; (c) K. E. Laidig, J. Phys. Chem., 1993, 97, 12 760.
24. (a) W. J. Hehre, L. Radom, P. v. R. Schleyer and J. A. Pople, Ab Initio Molecular Orbital Theory, Wiley, New York, 1986; (b) A. E. Reed, L. E. Curtiss and F. Weinhold, Chem. Rev., 1988, 88, 899; (c) C. M. Breneman and K. B. Wiberg, J. Comput. Chem., 1990, 11, 361.
25. D. J. Wales, A. J. Stone and P. L. A. Popelier, Chem. Phys. Lett., 1995, 240, 89 and references cited therein.
26. MP2/6-311 ++ G(d,p) optimisations of HN=CH₂ and H₂N–CH₃ give N–C distances of 1.281 and 1.465 Å, respectively. The analagous P–C distances are 1.857 and 1.673 Å.
27. T. Naito, S. Nagase and H. Yamataka, J. Am. Chem. Soc., 1994, 116, 10 080 and references cited therein.
28. L. Nyulászi, T. Veszprémi and J. Réffy, J. Phys. Chem., 1995, 99, 10 142.
29. J. Emsley, The Elements, OUP, New York, 1989; values of 1.85 and 1.20 Å are reported for C and H.
30. (a) J. Cosléou, D. G. Lister and A. C. Legon, Chem. Phys. Lett., 1994, 231, 151; (b) A. C. Legon, J. Chem. Soc., Faraday Discuss., 1994, 97, 19.
31. L. A. Curtiss, D. J. Frurip and M. Blander, J. Chem. Phys., 1979, 71, 2703.
32. Y–C bond CP properties in H₂N–CH₃, ρ= 0.261, ∇²ρ=–0.707, ε= 0.029; HN=CH₂, ρ= 0.375, ∇²ρ=–0.861, ε= 0.218; H₂P–CH₃, ρ= 0.151, ∇²ρ= 0.123, ε= 0.131; HP=CH₂, ρ= 0.184, ∇²ρ=+0.396, ε= 0.395.
33. M. T. Carroll, C. Chang and R. F. W. Bader, Mol. Phys., 1988, 63, 387.