Advisor: Jun Zhu Speaker: Xuerui Wang

Theoretical study on the interconversion of silabenzenes and their non-aromatic isomers via the

[1,3]-substituent shift: aromaticity vs Bent's rule

Bent's Rule Aromaticity

AromaticityBent' rule

SiO

RX

SiR OX

G = -28.5 ~ 122.2

kcal mol-1

Outline

Background

Computational Method

Results and Discussion

Conclusion4

1

2

3

Background

Text in here

Si

Ad

OTMS

TMS

TMSSi

Ad

OTMSTMS

TMS

hv

TMS = SiMe3Ad = 1-adamantyl

Figure 1.Photochemically Induced [1,3]-Trimethylsilyl Shift from Si to O Applied by Brook et al. to the Formation ofthe First Silene Stable at room temperature1. Brook, A. G.; Abdesaken, F.; Gutekunst, B.; Gutekunst, G.; Kallury, R. K. J. Chem. Soc., Chem. Commun. 1981,191. 2. Brook, A. G.; Nyburg, S. C.; Abdesaken, F.; Gutekunst, B.; Gutekunst, G.; Krishna, R.; Kallury, M. R.; Poon,Y. C.; Chang, Y. M.; Wong-Ng, W. J. Am. Chem. Soc. 1982, 104, 5667.

SiSiO

R3SiR3Si

R''R' R' R''

R'''R'''

OSiR3R3Si

R = Me or iPr

R' = H, Me, Et, iPr, tBu, OSiMe3

R'' = H, Me, Et, iPr, tBu

R''' = H, Me, tBu

Rouf, A. M.; Jahn, B. O.; Ottosson, H. Organometallics.2013, 32, 16.

Figure 2. Synthetic route to silabenzenes through the [1,3]-Si O TMS shift by Density functional theory (DFT) calculations

G= -11.1~ -22.6 kcal mol-1

Background

Rouf, A. M.; Jahn, B. O.; Ottosson, H. Organometallics.2013, 32, 16

driving force Aromaticity

G = 0.6 kcal/molSi SiO OSiMe3Me3Si

Me3SiMe3Si

Figure 3. [1,3]-Trimethylsilyl Shift Leading from 1,1-Bis(trimethylsilyl)-3,6-dimethylenesilacyclohexan-2-one to 1,1-Bis(trimethylsilyl)-3,6-dimethylene-2-(trimethylsiloxy) silacyclohex-1-ene

nonaromatic six membered ring

Kutzelnigg, W. Angew. Chem., Int. Ed. Engl. 1984, 23, 272.

silicon atom is reluctant to participate in bonding

Computational Method

Package :

Method :

basis sets :

Gaussian 09

M06-2X / B3LYP

6-311+G **

1.(a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Miehlich, B.; Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200. (c) Lee, C.; Yang, W.; Parr, G. Phys. ReV. B 1988, 37, 785. 2. Zhao,Y.; Truhlar, D. G. Theor. Chem. Acc. 2008, 120, 215.3. Frisch, M. J. et al. Gaussian, Inc., Wallingford CT, 2010.

DFT

Results and Discussion

Figure 4. The formation of silabenzenes through the [1,3]-Si→O substituent shift .

Bent’s rule : atomic s character tends to concentrate in orbitals that are directed toward electropositive groups and atomic p character tends to concentrate in orbitals that are directed toward electronegative groups.

(a) Bent, H. A. Chem. Rec.1961, 61, 275. (b) Zhu, J.; Lin, Z.; Marder, T. B. Inorg. Chem. 2005, 44, 9384.

1.928

1.481

1.346

1.472

1.343

1.8671.796

1.391

1.3971.396

1.393

1.770

1.934

1.482

1.346

1.474

1.344

1.8671.796

1.389

1.3971.397

1.394

1.775

SiSiO

H3SiH OHH3Si

G = -0.3SiSi

OH3Si

Me2N ONMe2H3Si

G = +46.8

a b

reluctance sp3

Results and Discussion

SiSiO

R1

X OXR1

X: H, NMe2, F, OMe, Cl, SMe, Me, GeH3, SiH3, AlH2

Set A: R1 = SiH3, Set B: R1 = Me

Figure 6. [1,3]-substituent shift for the formation of silabenzenes with various substituents.

SiOXH3Si

SiH2Si OX

X = H ISE = -25.3

X = NMe2 ISE = -28.3

Figure 5. The calculated ISE values of A1' and A2'.

NICS(0)zz -11.2 (X = H) -11.6 (X=NMe2)

Evaluate Aromaticity : ISE(isomerization stabilization energy) method and NICS( nucleus independent chemical shift) calculations

Results and DiscussionSilabenzene ΔG(298k)(kcal/mol) ΔSiC(ring) ΔCC(ring) NICS(0)zz Σα(Si)

1a(F) 117.8 0.021 0.008 -12.5 360.01b(OMe) 84.76 0.02 0.006 -11.9 360.01c(Cl) 77.15 0.02 0.017 -10.9 359.21d(NMe2) 46.76 0.02 0.005 -11.6 360.01e(SMe) 38.13 0.026 0.006 -12.0 360.01f(Me) 17.83 0.029 0.01 -11.9 360.01g(H) -0.33 0.026 0.006 -11.2 360.01h(GeH3) -0.8 0.033 0.004 -11.5 360.01i(SiH3) -16.08 0.031 0.005 -11.7 359.91j(AlH2) -29.32 0.026 0.005 -11.3 360.02a(F) 122.2 0.011 0.016 -9.2 360.02b(OMe) 90.2 0.024 0.009 -12.3 360.0

2c(Cl) 81.45 0.014 0.009 -10.0 359.8

2d(NMe2) 54.48 0.026 0.009 -12.0 360.02e(SMe) 42.38 0.029 0.012 -11.6 360.02f(Me) 22.29 0.031 0.003 -12.3 360.02g(H) 2.32 0.031 0.012 -11.8 360.02h(GeH3) 0.11 0.033 0.007 -11.8 360.02i(SiH3) -14.8 0.031 0.008 -11.9 360.02j(AlH2) -28.48 0.029 0.01 -11.5 360.0

SiR1 OX

SiO

R1

X

G

R1 = SiH3 (set 1) R1 = Me (set 2)

X = F (a) X = OMe (b) X = Cl (c) X = NMe2 (d) X = SMe(e) X = Me(f) X = H(g) X = GeH3 (h) X = SiH3 (i) X = AlH2(j)

Results and Discussion

Figure 7. The plot of s character of Si to the Si-X σ bond vs ΔG

Results and Discussion

Figure 8. The plot of s character of Si to the Si-X σ bond vs reaction barriers (ΔG)

Results and Discussion

Figure 9. Plot of reaction free energies (ΔG) against the percentage of the s character of Si in the Si-X bonds by replacing the acyl group with methylene group in acylsilane..

Results and Discussion

Figure 10. Plot of reaction free energies (ΔG) against the percentage of the s character of Si in the Si-X bonds in nonaromatic system.

Silabenzene (X)

ΔG ΔG' ΔG'-ΔG

A1' (H)A2' (NMe2)

-0.346.8

27.674.8

27.928.0

A3' (Me)A4' (SMe)A5' (Cl)A6' (OMe)A7' (F)A8' (GeH3)A9' (SiH3)A10' (AlH2)

B1' (H)B2' (NMe2)

B3' (Me)B4' (SMe)B5' (Cl)B6' (OMe)B7' (F)B8' (GeH3)B9' (SiH3)B10' (AlH2)

17.838.177.284.8117.8-0.8-16.1-29.32.354.522.342.481.590.2122.20.1-14.8-28.5

46.167.0105.9114.0147.426.812.5-2.232.983.951.173.3114.1121.8153.830.015.6-0.2

28.328.928.729.229.627.628.631.530.629.428.830.932.631.631.629.930.428.7

Conclusion

1. Aromaticity is not the only driving force for the

reaction.

2. Bent‘s rule plays an important role in formation

of the silabenzene.

3. Our findings could be a useful guide to the

synthesis of silabenzenes.

Thank You!