welcome professor lin to direct our group!

Welcome Professor Lin

to direct our group!

2

Self-introduction

Name: Yulei.Hao

Hometown: Shou County in Anhui Province

Mother school: Hefei University of Technology

合肥工业大学Grade: First-year graduate

σ-Aromaticity Review and σ-Aromaticity investigation of 3MRs transition metal

alkylidene complexes

Reportor: Yulei Hao

Advisor: Jun Zhu

Introduction of σ-Aromaticity 1

Computed methods2

Results and Discussion3

Further work4

4

Dewar firstly proposed the concept of σ-

Aromaticity to explain the anomalous behavior of

cyclopropane such as the upfield 1HNMR chemical

shift (1.25ppm to 0.22ppm), small difference of

CSE (conventional strain energy) compared with

cyclobutane , 27.5 kcal mol-1 and 26.5 kcal mol-1

respectively. He concluded that σ-Aromaticity

energy compensate the high strain energy, and σ-

ring induce the diamagnetic property.

5


cyclopropane

σ-Conjugation and σ-Aromaticity

M. J. Dewar, Bull. Soc. Chim. Belg.

1979, 88, 957-967

H

H

H

H

H

H

Figure1. Magnetic lines of force in cyclopropane.

6


The two structure models of cyclopropane

H2C CH2

CH2

Walsh Coulson and Moffitt

three trignal near-sp2 methylene carbenes three bent C(sp3)-C(sp3)bonds

7

　 author 　　　 concept 　　

　Method orconclusion

　　　

1979 Dewar σ-Aromaticityproposed σ-ring current and aromaticity energy

1985 Cremerelectron density and surface delocalization

ab initio caculation

1996 Schleyer NICS valuesabsolute magnetic shieldings coputed at ring centers

2001 Schleyerintrinsic bond energy

evaluate ASE (11.3 kal.mol-1)

2002 Schleyer ISE simple way to evaluation ASE

2005 SchleyerECRE(extra cyclic resonance energy)

evaluation ASE and correlated well with NICS

2007 Folwer σ-ring current coupled Hatree-Fock "ipsocentric"

2009Wu Wei and Schleyer

VBSCF motheod, ECRE 　　 small σ-ASE (3.5 kal mol-1) 　　


Table1. the deveiopment of cyclopropane of σ-Aromaticity and evaluation criteria.

8

J. Am. Chem. Soc. 1996, 118, 6317.


Theoretical Determination of Molecular Structure and Conformation. 1 5. Three-Membered Rings: Bent Bonds, Ring Strain, and Surface Delocalization

J. Am. Chem. Soc. 1985, 107, 13, 3805.Nucleus-Independent Chemical Shifts: A Simpleand Efficient Aromaticity Probe

Is Cyclopropane Really the s-Aromatic Paradigm?

Chem. Eur. J. 2009, 15 9730-9736.

Theoretical Bond Energies: A Critical Evaluation

J. Phys. Chem. A 2001, 105, 3407-3416.

References:

The ring current in cyclopropane Theor. Chem. Acc. 2007, 118, 123-127.

Recommendations for the Evaluation of Aromatic Stabilization Energies Org. Lett. 2002, 4, 2873-2876.An Energetic Measure of Aromaticity andAntiaromaticity Basedon thePauling–Wheland Resonance. Chem. Eur. J. 2006, 12, 2009-2020.

9

Org. Lett.Vol. 2002, 4, 2873-2876

Recommendations for the Evaluation of Aromatic Stabilization Energies

ISE: isomeric stabilization energy

The differences between a methyl derivative of the aromatic

system and its nonaromatic exocyclic methylene isomer.


ISE=35.3kcal/mol

10

ECRE: extra cyclic resonance energy

The RE (resonance energy) difference between a fully

cyclic aromatic compound and appropriate acyclic model.

X X

ERc

X ERa

X

ECRE= ERc - ER

a


An Energetic Measure of Aromaticity and Antiaromaticity Based on the Pauling–Wheland Resonance. Chem. Eur. J. 2006, 12, 2009-2020.

11


a b Fig. 3 a Current density map for cyclopropane. b the sum of localised C–H bonds of the cyclopropane molecule. The current induced in the plane of the carbon nuclei by a perpendicular external magnetic field is calculated at the (CTOCD-DZ/ 6-31G**//RHF/6-31G**) level.

The ring current in cyclopropane. Patrick W. Fowler Theor. Chem. Acc. 2007, 118, 123-127.

12

Computed Methods2

OptDFT: B3LYPBase sets: 6-31G* and LanL2DZ

NICS DFT: B3LYPBase sets: 6-311++G** and LanL2DZ

ASEDFT: B3LYPBase sets: 6-31G* and LanL2DZ

13

Mn

O

H2N

OC

OC CO

Mn(4)

NH2

1.908

2.18

7

2.19

2

2.25

3

1.430

1.4101.414

FeOC

OC CO

NH2

NH2

Fe(5)

O

1.89

2

2.28

6

1.94

9

1.406

1.4597

Cr

O

H2N

H2N

NH2

O

Cr(6)

1.873

2.193

1.437

Nb

OH3SiNH

H3Si

H2P PH

ClH2P PH2

2.073

2.0971.357

Nb(7)

benzene(1)

1.398

cycloprapene(2)

1.2921.

510

1.51

0

cyclopropane(3)

1.509

W

F3C

F3C

W.1(8)

CF3

CF3

Cl

Cp

C

NH

1.926

2.567

1.48

3

2.075

2.058

1.30

5

W COOC

F3C

CF3

FNH2NF

F

F F

W.2(9)

1.951

2.224

1.442

WPh

Cl

ON

Cp

W.3(10)

2.087

2.675

1.35

7

Mo

H3P

H3P

Cp

Mo.1(11)

1.9382.303

1.42

5

Mo CF3

CF3

Cp

Mo.3(13)

F3C

F3C

N

S

2.133

1.29

0

1.919

2.224 1.41

9

2.089

Mo

H3P

H3P

Cp

Mo.2(12)

1.946

2.278

1.42

9

SiH3


14

Re

H3P

H3P

PH3

Cl

Re.1(16)

1.995

2.219

1.3181.3

76

1.41

9

1.395

2.051

Re

PH2

PH2

Cp

Re.2(17)

1.902

2.273

1.40

8

ReOC

Re.3(18)

Cp

CO

1.975

2.264

1.40

5

OsH

Os.1(14)

PH3

PH3

O

O

1.932Ph

OsH

PH3

PH3

O

F

F

F

F

Ph

Os.2(15)

1.977

2.167

1.41

3


15

　 NICS(0) NICS(0)ZZ NICS(1) a NICS(1)ZZ b

1 -8.1 -14.5 -10.2 -29.12 -28.3 -18.2 -6.9 -15.13 -42.4 -29.8 -8.6 -24.24 -33.8 -59.1 -18.8 -21.45 -20.2 -41.7 -13.5 -16.96 -39.5 -65.6 -18.9 -24.97 -31.6 -54.6 -24.1 -35.98 -25.2 -21.2 -17.6 -20.29 -35.7 -51.5 -16.5 -22.4

10 -13.2 -25.5 -9.6 -11.511 -36.6 -60.5 -20.2 -29.612 -36.0 -63.0 -18.4 -28.113 -33.5 -55.3 -17.1 -25.814 -47.5 -65.4 -19.2 -30.015 -33.2 -42.4 -16.3 -24.416 -45.5 -69.6 -18.5 -25.717 -39.0 -49.0 -19.1 -25.818 -31.7 -41.2 -17.0 -24.4

Table 2. NICS values [ppm] of non-metal rings1-3 and alkylidene compelexes rings 4-18.

a, b These are the average values of above and below center(0) 1Å.


16


Fig. 4 Comparison of NICS(0) with NICS(1), and NICS(0)ZZ with NICS(1)ZZ based on the result in table 2.

Benzene

17


Mn

O

H2N

OC

OC CO

NH2 +

Mn

O

H2N

OC

OC CONH2

27.8

FeOC

OC CO

NH2

NH2

O

FeOC

OC CO

NH2

NH2

O

+ 30.6

W

PhCl

ON

Cp

+ W

Cl

ON

CpPh

49.6

Re

OC

Cp

CO

+Re

OC

Cp

CO20.5

Cr

O

H2N

H2N

NH2

OH+

Cr

O

H2N

H2NO

H2N

32.5

18

Further work4

• Try to find other ways to evaluate σ-Aromaticity

energy by VB.

• Explain the NICS results reasonably.

19

Thank you !

welcome professor lin to direct our group!

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