Theoretical Study on the Aromaticity of Metallasilapentalynes

Advisor: Jun Zhu Reporter: Xuerui Wang

pentalyne metallapentalyne metallasilapentalyneIII

Antiaromatic Aromatic Aromatic

III

[M] Si[M]?

Outline

Background

Computational Method

Results and Discussion

Conclusion

Background

1982Os(CO)(CS)(PPh3)3 + 2HCCH

Os

PPh3

PPh3S

CO

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

Mn

L

L

LRh

L

L

Cl

ClRh

L

L

LL

L is a neutral 2e- donor ligand

OsCl2(PPh3)3 + excess SiMe3H

Os

PPh3Cl

ClPPh3

SiMe3

Me

SiMe3

pentalynepentalene

antiaromaticity8e

distorted triple bondextremely strained

116destabilization

metallapentalyne

[M]

[M]=OsCl(PH3)2

10e aromaticity

129.5reduce the ring strain significantly

Introduce a metal into the ring

X-ray molecular structure

C-C bond lengths 1.377-1.402Ǻ

Planar eight-membered metallabicycleBenzene 1.396Ǻ

The aromaticity of osmapentalyne

2A2B 2C

2E2D

R = COOMe[Os] = OsCl(PPh3)2

[Os]

R PPh3

[Os]

R PPh3

[Os]

R PPh3

[Os]R PPh3

[Os]

R PPh3

This feature suggests an aromatic π conjugation result from resonance structure

6.59

5.83

5.60

6.68

H

H

H

H[Os]

R PPh3

H

H H7.66 (8.32)8.90 (9.27)

12.78 (14.25)

Down-field H chemical shifts

C NMR a lower field than osmabenzynes

Si[M]

silicon atom is reluctant to participate in bonding

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

?

M SiWhy Mδ--Siδ+

Frederick, P.; Arnold, J. Organometallics 1999, 18, 4800.

σ-donation/weak π-back donation

Ccarb. (pz)

M(d)

M C

sp2

+ +

_ _

d pz

Fischer carbene，M→L is limited.

show high reactivities toward nucleophiles

Okazaki, M.; Tobita, H.; Ogino, H. Dalton Trans. 2003, 493.

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.

Results and Discussion

Stability comparison which silicon in different positions of the ring

Os Si OsSi

Os

Si

Si Os

10.536.6 29.20.0

Os

Si

Os

Si

OsSi

19.6 20.5 34.9

Ru Si RuSi

Ru

Si

Si RuRu

Si

Ru

Si

RuSi

0.0 50.5 29.2 30.9 37.6 46.3 16.9

(kcal/mol)

Os

Si

PH3

PH3

Cl

A

B2.299

1.8091.381

1.429

1.382

1.4201.363

2.035

2.147

112.6

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

Ru

Si

PH3

PH3

Cl

A

B

2.280

1.8071.380

1.427

1.376

1.4251.357

2.028

2.166

114.7

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)

the nucleus-independent chemical shift (NICS) values for each ring by DFT calculations

Ring A;NICS(0) = - 7.3 NICS(1) = - 9.8NICS(2) = - 5.9NICS(-1) = - 10.0NICS(-2) = - 6.2NICS(1)zz = - 19.8

Ring B:NICS(0) = - 8.9NICS(1) = - 8.8NICS(2) = - 4.1NICS(-1) = - 9.1NICS(-2) = - 4.2NICS(1)zz = - 16.2

Ring A;NICS(0) = - 5.0 NICS(1) = - 7.6NICS(2) = - 5.2NICS(-1) = - 7.7NICS(-2) = -5.3NICS(1)zz = -15.3

Ring B:NICS(0) = - 7.5NICS(1) = - 7.7NICS(2) = - 3.7NICS(-1) = -7.8NICS(-2) = -3.7NICS(1)zz = -13.4

Figure 3. the NICS values of the each ring

A B

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

[Os] E

(E = Si)

(E = Si)

(E = Si)

[Os] E (E = Si)

[Os]=OsCl(PH3)2

(E = C)

(E = C)

(E = C)

(E = C)

[Os] E

[Os] E [Os] E

[Os] E[Os] E

[Os] E

ISE= - 22.8

ISE= - 23.3

ISE= - 21.2

ISE= - 19.6

ISE = -18.3

ISE= - 17.5

ISE= - 16.5

ISE= - 16.9

[Ru] E

(E = Si)

(E = Si)

(E = Si)

[Ru] E (E = Si)

[Ru]=RuCl(PH3)2

(E = C)

(E = C)

(E = C)

(E = C)

[Ru] E

[Ru] E [Ru] E

[Ru] E[Ru] E

[Ru] E

ISE= - 22.6

ISE= - 23.5

ISE= - 20.2

ISE= - 21.6

ISE= - 17.3

ISE= - 16.1

ISE= - 15.0

ISE= - 16.8

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

?

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

Si[Ru] HSi[Ru] Cl [Os] Si [Os] Si

Cl

Os Si

Cl

0.0

[Os] SiCl

-6.1

23.6

33.5

[Os] Si[Os] Si

Cl

[Os] Si

Cl

25.6TS1

TS2

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