Evidence for d orbital aromaticity in square planar coinage metal clusters

Journal of the American Chemical Society

Volumn 127, Issue 15, 2005, Pages 5701-5705

  Wannere, Chaitanya S ^a   Corminboeuf, Clémence ^a   Wang, Zhi Xiang ^a   Wodrich, Matthew D ^a   King, R Bruce ^a   Schleyer, Paul V R ^a  

^a UNIVERSITY OF GEORGIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CHEMICAL BONDS; ELECTRON ENERGY LEVELS; LITHIUM COMPOUNDS; TRANSITION METAL COMPOUNDS;

AROMATICITY; ATOMIZATION ENERGY; CHEMICAL SHIFTS; COINAGE METAL CLUSTERS; D ORBITALS;

AROMATIC COMPOUNDS;

COPPER DERIVATIVE; GOLD; SILVER; TRANSITION ELEMENT;

ARTICLE; ELECTRON; ENERGY; PROTON NUCLEAR MAGNETIC RESONANCE; QUANTITATIVE ANALYSIS;

EID: 17644374072     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja042716q     Document Type: Article

References (61)

1. (a) Shaik, S.; Hiberty, P. C. J. Am. Chem. Soc. 1985, 107, 3089.
2. (b) Hiberty, P. C.; Danovich, D.; Shurki, A.; Shaik, S. J. Am. Chem. Soc. 1995, 117, 7760. See footnote 26b in the latter article.
3. Robinson, G. H. Acc. Chem. Res. 1999, 32, 773.
4. Li, X.; Kuznetsov, A. E.; Zhang, H. F.; Boldyrev, A. I.; Wang, L. S. Science 2001, 291, 859.
5. Chandrasekhar, J.; Jemmis, E. D.; Schleyer, P. v. R. Tetrahedron Lett. 1979, 3707-3710.
6. (a) Kuznetsov, A. E.; Boldyrev, A. I.; Li, X.; Wang, L. S. J. Am. Chem. Soc. 2001, 123, 8825.
7. (b) Boldyrev, A. I.; Kuznetsov, A. E. Inorg. Chem. 2002, 41, 532.
8. (c) Kuznetsov, A. E.; Birch, K. A.; Boldyrev, A. I.; Li, X.; Zhai, H. J.; Wang, L. S. Science 2003, 300, 622.
9. (d) Fowler, P. W.; Havenith, R. W. A.; Steiner, E. Chem. Phys. Lett. 2001, 342, 85.
10. (e) Fowler, P. W.; Havenith, R. W. A.; Steiner, E. Chem. Phys. Lett. 2002, 359, 530.
11. (f) Juselius, J.; Straka, M.; Sundholm, D. J. Phys. Chem. A 2001, 105, 9939.
12. (g) Chen, Z. F.; Corminboeuf, C.; Heine, T.; Bohmann, J.; Schleyer, P. v. R. J. Am. Chem. Soc. 2003, 125, 13930.
13. Li, X.; Zhang, H. F.; Wang, L. S.; Kuznetsov, A. E.; Cannon, N. A.; Boldyrev, A. I. Angew. Chem., Int. Ed. 2001, 40, 1867.
14. Kuznetsov, A. E.; Corbett, J. D.; Wang, L. S.; Boldyrev, A. I. Angew. Chem., Int. Ed. 2001, 40, 3369.
15. (a) Tsipis, A. C.; Tsipis, C. A. J. Am. Chem. Soc. 2003, 125, 1136.
16. 4 larger than that reported by Tsipis (-4.8) at GIAO-B3LYP/6-311+G(d, p)// B3LYP/6-311+G(d,p).
17. Clusters involving Cu, Ag, and Au also have been explored. For example: (a) Tsipis, C. A.; Karagiannis, E. E.; Kladou, P. F.; Tsipis, A. C. J. Am. Chem. Soc. 2004, 126, 12916. (b) Matulis, V. E.; Ivashkevich, O. A.; Gurin, V. S. J. Mol. Struct. (THEOCHEM) 2004, 681, 169. (c) Tanaka, H.; Neukermans, S.; Janssens, E.; Silverans, R. E.; Lievens, P. J. Am. Chem. Soc. 2003, 125, 2862. (d) Häkkinen, H.; Yoon, B.; Landman, U.; Li, X.; Zhai, H.-J.; Wang, L.-S. J. Phys. Chem. A 2003, 107, 6168. (e) Furche, F.; Ahlrichs, R.; Weis, P.; Jacob, C.; Gilb, S.; Bierweiler, T.; Kappes, M. M. J. Chem. Phys. 2002, 117, 6982.
18. Clusters involving Cu, Ag, and Au also have been explored. For example: (a) Tsipis, C. A.; Karagiannis, E. E.; Kladou, P. F.; Tsipis, A. C. J. Am. Chem. Soc. 2004, 126, 12916. (b) Matulis, V. E.; Ivashkevich, O. A.; Gurin, V. S. J. Mol. Struct. (THEOCHEM) 2004, 681, 169. (c) Tanaka, H.; Neukermans, S.; Janssens, E.; Silverans, R. E.; Lievens, P. J. Am. Chem. Soc. 2003, 125, 2862. (d) Häkkinen, H.; Yoon, B.; Landman, U.; Li, X.; Zhai, H.-J.; Wang, L.-S. J. Phys. Chem. A 2003, 107, 6168. (e) Furche, F.; Ahlrichs, R.; Weis, P.; Jacob, C.; Gilb, S.; Bierweiler, T.; Kappes, M. M. J. Chem. Phys. 2002, 117, 6982.
19. Clusters involving Cu, Ag, and Au also have been explored. For example: (a) Tsipis, C. A.; Karagiannis, E. E.; Kladou, P. F.; Tsipis, A. C. J. Am. Chem. Soc. 2004, 126, 12916. (b) Matulis, V. E.; Ivashkevich, O. A.; Gurin, V. S. J. Mol. Struct. (THEOCHEM) 2004, 681, 169. (c) Tanaka, H.; Neukermans, S.; Janssens, E.; Silverans, R. E.; Lievens, P. J. Am. Chem. Soc. 2003, 125, 2862. (d) Häkkinen, H.; Yoon, B.; Landman, U.; Li, X.; Zhai, H.-J.; Wang, L.-S. J. Phys. Chem. A 2003, 107, 6168. (e) Furche, F.; Ahlrichs, R.; Weis, P.; Jacob, C.; Gilb, S.; Bierweiler, T.; Kappes, M. M. J. Chem. Phys. 2002, 117, 6982.
20. Clusters involving Cu, Ag, and Au also have been explored. For example: (a) Tsipis, C. A.; Karagiannis, E. E.; Kladou, P. F.; Tsipis, A. C. J. Am. Chem. Soc. 2004, 126, 12916. (b) Matulis, V. E.; Ivashkevich, O. A.; Gurin, V. S. J. Mol. Struct. (THEOCHEM) 2004, 681, 169. (c) Tanaka, H.; Neukermans, S.; Janssens, E.; Silverans, R. E.; Lievens, P. J. Am. Chem. Soc. 2003, 125, 2862. (d) Häkkinen, H.; Yoon, B.; Landman, U.; Li, X.; Zhai, H.-J.; Wang, L.-S. J. Phys. Chem. A 2003, 107, 6168. (e) Furche, F.; Ahlrichs, R.; Weis, P.; Jacob, C.; Gilb, S.; Bierweiler, T.; Kappes, M. M. J. Chem. Phys. 2002, 117, 6982.
21. Clusters involving Cu, Ag, and Au also have been explored. For example: (a) Tsipis, C. A.; Karagiannis, E. E.; Kladou, P. F.; Tsipis, A. C. J. Am. Chem. Soc. 2004, 126, 12916. (b) Matulis, V. E.; Ivashkevich, O. A.; Gurin, V. S. J. Mol. Struct. (THEOCHEM) 2004, 681, 169. (c) Tanaka, H.; Neukermans, S.; Janssens, E.; Silverans, R. E.; Lievens, P. J. Am. Chem. Soc. 2003, 125, 2862. (d) Häkkinen, H.; Yoon, B.; Landman, U.; Li, X.; Zhai, H.-J.; Wang, L.-S. J. Phys. Chem. A 2003, 107, 6168. (e) Furche, F.; Ahlrichs, R.; Weis, P.; Jacob, C.; Gilb, S.; Bierweiler, T.; Kappes, M. M. J. Chem. Phys. 2002, 117, 6982.
22. (a) Jarvis, J. A. J.; Pearce, R.; Lappert, M. F. J. Chem. Soc., Dalton Trans. 1977, 999.
23. (b) Meyer, E. M.; Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. Organometallics 1989, 8, 1067.
24. Diamagnetic and paramagnetic ring current effects associated with aromaticity and antiaromaticity, respectively, are measured simply and effectively by NICS. NICS is based on the absolute magnetic shieldings computed at ab initio, DFT, and semiempirical (MNDO) levels; the signs are reversed to conform with the NMR chemical shift convention. Significantly negative NICS values in interior positions of ring or cages indicate aromaticity, whereas positive values denote antiaromaticity. See: (a) Schleyer, P. v. R.; Maerker, C.; Dransfeld, A.; Jiao, H.; Hommes, N. J. R. v. E. J. Am. Chem. Soc. 1996, 118, 6317. (b) Schleyer, P. v. R.; Jiao, H.; Hommes, N. J. R. v. E.; Malkin, V. G.; Malkina, O. L. J. Am. Chem. Soc. 1997, 119, 12669. (c) Schleyer, P. v. R.; Manoharan, M.; Wang, Z. X.; Kiran, B.; Jiao, H.; Puchta, R.; Hommes, N. J. R. v. E. Org. Lett. 2001, 3, 2465. (d) Wannere, C. S.; Corminboeuf, C.; Allen, W. D.; Schaefer, H. F., III; Schleyer, P. v. R. Org. Lett., published online March 17, 2005 http://dx.doi.org/10.1021/o1050118q.
25. Diamagnetic and paramagnetic ring current effects associated with aromaticity and antiaromaticity, respectively, are measured simply and effectively by NICS. NICS is based on the absolute magnetic shieldings computed at ab initio, DFT, and semiempirical (MNDO) levels; the signs are reversed to conform with the NMR chemical shift convention. Significantly negative NICS values in interior positions of ring or cages indicate aromaticity, whereas positive values denote antiaromaticity. See: (a) Schleyer, P. v. R.; Maerker, C.; Dransfeld, A.; Jiao, H.; Hommes, N. J. R. v. E. J. Am. Chem. Soc. 1996, 118, 6317. (b) Schleyer, P. v. R.; Jiao, H.; Hommes, N. J. R. v. E.; Malkin, V. G.; Malkina, O. L. J. Am. Chem. Soc. 1997, 119, 12669. (c) Schleyer, P. v. R.; Manoharan, M.; Wang, Z. X.; Kiran, B.; Jiao, H.; Puchta, R.; Hommes, N. J. R. v. E. Org. Lett. 2001, 3, 2465. (d) Wannere, C. S.; Corminboeuf, C.; Allen, W. D.; Schaefer, H. F., III; Schleyer, P. v. R. Org. Lett., published online March 17, 2005 http://dx.doi.org/10.1021/o1050118q.
26. Diamagnetic and paramagnetic ring current effects associated with aromaticity and antiaromaticity, respectively, are measured simply and effectively by NICS. NICS is based on the absolute magnetic shieldings computed at ab initio, DFT, and semiempirical (MNDO) levels; the signs are reversed to conform with the NMR chemical shift convention. Significantly negative NICS values in interior positions of ring or cages indicate aromaticity, whereas positive values denote antiaromaticity. See: (a) Schleyer, P. v. R.; Maerker, C.; Dransfeld, A.; Jiao, H.; Hommes, N. J. R. v. E. J. Am. Chem. Soc. 1996, 118, 6317. (b) Schleyer, P. v. R.; Jiao, H.; Hommes, N. J. R. v. E.; Malkin, V. G.; Malkina, O. L. J. Am. Chem. Soc. 1997, 119, 12669. (c) Schleyer, P. v. R.; Manoharan, M.; Wang, Z. X.; Kiran, B.; Jiao, H.; Puchta, R.; Hommes, N. J. R. v. E. Org. Lett. 2001, 3, 2465. (d) Wannere, C. S.; Corminboeuf, C.; Allen, W. D.; Schaefer, H. F., III; Schleyer, P. v. R. Org. Lett., published online March 17, 2005 http://dx.doi.org/10.1021/o1050118q.
27. Diamagnetic and paramagnetic ring current effects associated with aromaticity and antiaromaticity, respectively, are measured simply and effectively by NICS. NICS is based on the absolute magnetic shieldings computed at ab initio, DFT, and semiempirical (MNDO) levels; the signs are reversed to conform with the NMR chemical shift convention. Significantly negative NICS values in interior positions of ring or cages indicate aromaticity, whereas positive values denote antiaromaticity. See: (a) Schleyer, P. v. R.; Maerker, C.; Dransfeld, A.; Jiao, H.; Hommes, N. J. R. v. E. J. Am. Chem. Soc. 1996, 118, 6317. (b) Schleyer, P. v. R.; Jiao, H.; Hommes, N. J. R. v. E.; Malkin, V. G.; Malkina, O. L. J. Am. Chem. Soc. 1997, 119, 12669. (c) Schleyer, P. v. R.; Manoharan, M.; Wang, Z. X.; Kiran, B.; Jiao, H.; Puchta, R.; Hommes, N. J. R. v. E. Org. Lett. 2001, 3, 2465. (d) Wannere, C. S.; Corminboeuf, C.; Allen, W. D.; Schaefer, H. F., III; Schleyer, P. v. R. Org. Lett., published online March 17, 2005 http://dx.doi.org/10.1021/o1050118q.
28. (a) Doedens, R. J. Prog. Inorg. Chem. 1976, 21, 209.
29. (b) Cairns, C. J.; Busch, D. H. Coord. Chem. Rev. 1986, 69, 1.
30. (a) Lockhart, T. P.; Haitko, D. A. Polyhedron 1985, 4, 1745.
31. (b) Iijima, K.; Itoh, T.; Shibata, S. J. Chem. Soc., Dalton Trans. 1985, 2555.
32. (c) Toth, A.; Floriani, C.; Chiesivilla, A.; Guastini, C. Inorg. Chem. 1987, 26, 236.
33. (d) Sorrele, T. N.; Brook, A. S. J. Am. Chem. Soc. 1987, 109, 4255.
34. Barden, C. J.; Rienstra-Kiracofe, J. C.; Schaefer, H. F. J. Chem. Phys. 2000, 113, 690.
35. (a) Bednorz, J. G.; Müller, K. A. Z. Phys. B: Condens. Matter 1986, 64, 189.
36. (b) Williams, J. M.; Beno, M. A.; Carlson, K. D.; Geiser, U.; Ivy Kao, H. C.; Kini, A. M.; Porter, L. C.; Schultz, A. J.; Thorn, R. J.; Wang, H. H.; Whangbo, M.-H.; Evain, M. Acc. Chem. Res. 1988, 21, 1.
37. (a) Poole, C. P.; Datta, T.; Farach, H. A. Copper Oxide Superconductors: Wiley: New York, 1988.
38. c Cuprates; Princeton University Press: Princeton, NJ, 1997.
39. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
40. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
41. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
42. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
43. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
44. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
45. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
46. For example, see: (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry; Wiley-Interscience. New York, 1988. (b) Schmidbaur, H.; Mandl, J. R.; Frank, A.; Huttner, G. Chem. Ber. 1976, 109, 466. (c) Uson, R.; Laguna, A.; Laguna, M.; Tarton, M. T.; Jones, P. G. J. Chem. Soc., Chem. Commun. 1988, 740. (d) Bardaji, M.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Laguna, M. Organometallics 1994, 13, 3415. (e) Knoepfler, A.; Wurst, K.; Peringer, P. J. Chem. Soc., Chem. Commun. 1995, 131. (f) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71. (g) Bardaji, M.; Cerrada, E.; Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans. 1997, 2263. (h) Bosch, E.; Barnes, C. L. Inorg. Chem. 2002, 41, 2543.
47. (a) Bohmann, J. A.; Weinhold, F.; Farrar, T. C. J. Chem. Phys. 1997, 107, 1173, and for more details on the CMO-NICS (canonical molecular orbital-NICS uses the NBO program to individually characterize the magnetic character of each canonical MO) method,
48. see: (b) Heine, T.; Schleyer, P. v. R.; Corminboeuf, C.; Seifert, G.; Reviakine, R.; Weber, J. J. Phys. Chem. A 2003, 107, 6470.
49. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, revision C.02; Gaussian. Inc.: Wallingford, CT, 2004.
50. 4h) are not presented here since it has five imaginary vibrational frequencies and an unstable wave function.
51. u orbital set.
52. Corminboeuf, C.; King, R. B.; Schleyer, P. v. R. J. Am. Chem. Soc., submitted for publication.
53. (a) Pyykko, P.; Desclaux, J. P. Acc. Chem. Res. 1979, 12, 276.
54. (b) Ziegler, T.; Snijders, J. G.; Baerends, E. J. Chem. Phys. Lett. 1980, 75, 1.
55. Balasubramanian, K. J. Mol. Struct. (THEOCHEM) 1989, 202, 291.
56. (a) Hall, K. K.; Mingos, D. M. P. Prog. Inorg. Chem. 1984, 32, 237.
57. (b) Mingos, D. M. P.; Watson, M. J. Adv. Inorg. Chem. 1992, 39, 327.
58. (c) Pignolet, L. H.; Aubart, M. A.; Craighead, K. L.; Gould, R. A. T.; Krogsted, D. A.; Wiley, J. S. Coord. Chem. Rev. 1995, 143, 219.
59. (a) Li, J.; Li, X.; Zhai, H. J.; Wang, L. S. Science 2003, 299, 864.
60. (b) Li, X.; Kiran, B.; Li, J.; Zhai, H. J.; Wang, L. S. Angew. Chem., Int. Ed. 2002, 41, 4786.
61. (c) Boyen, H. G.; Kastle, G.; Weigl, F.; Koslowski, B.; Dietrich, C.; Ziemann, P.; Spatz, J. P.; Riethmuller, S.; Hartmann, C.; Moller, M.; Schmid, G.; Garnier, M. G.; Oelhafen, P. Science 2002, 297, 1533.