Theoretical Study on the - PowerPoint Presentation

Slide1

Theoretical Study on the Aromaticity of Metallasilapentalynes

Advisor: Jun Zhu Reporter: Xuerui WangSlide2

Outline

Background Computational Method

Results and Discussion

Conclusion Slide3

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

, 811Tingbin Wen, Guochen Jia, Angew. Chem. Int. Ed, 2001, 40, 1951 Slide4

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 structureSlide5

C-C bond lengths 1.377-1.402Ǻ

Planar eight-membered metallabicycle

Benzene 1.396

Ǻ

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.Slide6

Why M

δ--Siδ+

Frederick, P.; Arnold, J.

Organometallics

1999

,

18

, 4800.

σ-donation/weak

π

-back donation

Fischer carbene

，M

→L is limited.

Slide7

show high reactivities toward nucleophiles

Okazaki, M.; Tobita, H.; Ogino, H.

Dalton Trans

.

2003

, 493.Slide8

Computational Method

DFTPackage : Gaussian 03Method: B3LYPbasis 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.Slide9

Results and Discussion

Stability comparison which silicon in different positions of the ring

(kcal/mol)Slide10

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 Slide11

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)Slide12

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) = - 9.1NICS(-2) = - 4.2NICS(1)zz = - 16.2

Ring A;NICS(0) = - 5.0 NICS(1) = - 7.6NICS(2) = - 5.2

NICS(-1) = - 7.7NICS(-2) = -5.3NICS(1)zz = -15.3

Ring B:NICS(0) = - 7.5

NICS(1) = - 7.7NICS(2) = - 3.7NICS(-1) = -7.8NICS(-2) = -3.7

NICS(1)zz = -13.4

Figure 3. the NICS values of the each ring

A

BSlide13

Isomerization stabilization energies (kcal/mol) of metallasilapentalyne compare to metallapentalyne

Figure 4

.

Isomerization stabilization energies (kcal/mol) of metallasilapentalyne compare to metallapentalyne

. Slide14

Figure 5

. the transition of the osmasilapentalyne and (Si)-Cl -osmasilapentaleneSlide15

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.Slide16

16

Thank you