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Theoretical Study on the Aromaticity of Metallasilapentalynes
Advisor: Jun Zhu Reporter: Xuerui Wang
pentalyne metallapentalyne metallasilapentalyneIII
Antiaromatic Aromatic Aromatic
III
[M] Si[M]?
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Outline
Background
Computational Method
Results and Discussion
Conclusion
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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
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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
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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.
?
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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.
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show high reactivities toward nucleophiles
Okazaki, M.; Tobita, H.; Ogino, H. Dalton Trans. 2003, 493.
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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.
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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)
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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
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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)
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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
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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 .
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?
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
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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.
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