1. Theoretical Study on the Aromaticity of Metallasilapentalynes Advisor: Jun Zhu Reporter: Xuerui Wang

2. Outline Background Computational Method Results and Discussion Conclusion

3. Background 1982 Thorn,D, L.; Hoffman, R. Nouv. J. Chim.1979, 3, 39. 1979 2001 G.P. Elliott, W.R. Roper, J. M. Waters, J. Chem. Soc. Chem.Commun, 1982, 811 Tingbin Wen, Guochen Jia, Angew. Chem. Int. Ed, 2001, 40, 1951

4. antiaromaticity 8e distorted triple bond extremely strained 116 destabilization 10e aromaticity 129.5 reduce the ring strain significantly Introduce a metal into the ring X-ray molecular structure

5. C-C bond lengths 1.377-1.402Ǻ Planar eight-membered metallabicycle Benzene 1.396Ǻ The aromaticity of osmapentalyne This feature suggests an aromatic π conjugation result from resonance structure Down-field H chemical shifts C NMR a lower field than osmabenzynes silicon atom is reluctant to participate in  bonding Kutzelnigg, W. Angew. Chem., Int. Ed. Engl. 1984, 23, 272.

6. Why M δ- -Si δ+ Frederick, P.; Arnold, J. Organometallics 1999, 18, 4800. σ -donation/weak π -back donation Fischer carbene ， M→L is limited.

7. show high reactivities toward nucleophiles Okazaki, M.; Tobita, H.; Ogino, H. Dalton Trans. 2003, 493.

8. Computational Method DFT Package : Gaussian 03 Method: B3LYP basis sets : 6-311++G ** LanL2DZ: Ru(ζ(f) = 1.235), Os(ζ(f) = 0.886),P(ζ(d) = 0.340), Cl(ζ(d) = 0.514), Si(ζ(d) = 0.262). 1. Ehlers, A. W.; Böhme, M.; Dapprich, S.; Gobbi, A.; Höllwarth, A.; Jonas, V.; Köhler, K. F.; Stegmann, R.; Veldkamp, A.; G., F. Chemical Physics Letters, 1993, 208, 111. 2. Check, C. E.; Faust, T. O.; Bailey, J. M.; Wright, B. J. J. Phys. Chem. A 2001, 105, 8111.

9. Results and Discussion Stability comparison which silicon in different positions of the ring (kcal/mol)

10. HOMO (-5.67ev)HOMO-1(-5.90ev) HOMO-2 (-6.14ev)HOMO-3 (-6.96ev) HOMO-12(-9.96ev)HOMO-8(-8.63ev) Figure 1.optimized structure of osmasilapentalyne and the occupied  MOs together with their energies

11. Figure 2.optimized structure of ruthenasilapentalyne and the occupied  MOs together with their energies HOMO(-5.82ev) HOMO-1(-6.01ev) HOMO-2(-6.24ev ) HOMO-3(-7.10ev) HOMO-8(-8.58ev) HOMO-12(-9.98ev)

12. the nucleus-independent chemical shift (NICS) values for each ring by DFT calculations Ring A; NICS(0) = - 7.3 NICS(1) = - 9.8 NICS(2) = - 5.9 NICS(-1) = - 10.0 NICS(-2) = - 6.2 NICS(1)zz = - 19.8 Ring B: NICS(0) = - 8.9 NICS(1) = - 8.8 NICS(2) = - 4.1 NICS(-1) = - 9.1 NICS(-2) = - 4.2 NICS(1)zz = - 16.2 Ring A; NICS(0) = - 5.0 NICS(1) = - 7.6 NICS(2) = - 5.2 NICS(-1) = - 7.7 NICS(-2) = -5.3 NICS(1)zz = -15.3 Ring B: NICS(0) = - 7.5 NICS(1) = - 7.7 NICS(2) = - 3.7 NICS(-1) = -7.8 NICS(-2) = -3.7 NICS(1)zz = -13.4 Figure 3. the NICS values of the each ring AB

13. Isomerization stabilization energies (kcal/mol) of metallasilapentalyne compare to metallapentalyne Figure 4. Isomerization stabilization energies (kcal/mol) of metallasilapentalyne compare to metallapentalyne.

14. Figure 5. the transition of the osmasilapentalyne and (Si)-Cl -osmasilapentalene

15. Conclusion From the view of π molecular orbitals and negative NICS values compared to benzene both reveal aromaticity in osmasilapentalyne and ruthenasilapentalyne. And the large negative ISEs can also indicate aromaticity. From the view of thermodynamics, the Cl atom has the possiblity to migrate, but from the figure 5 we can see there are high energy barrier to climb, so from the dynamics, the migration may be difficult.

16. 16