Prof. Simon AldridgeOxford UniversityPostdoc

w. Thomas Fehlner (U Notre Dame)

w. Michael Mingos (Imperial Col. London)

Ph.D. in 1996

w. Anthony Downs@Oxford U

Graduated Oxford U

TOC

C–C

Al

C–C

Abstract: The activation of C–C bonds is of fundamental interest in the

construction of complex molecules from petrochemical feedstocks. In the case

of the archetypal aromatic hydrocarbon benzene, C–C cleavage is

thermodynamically disfavored, and is brought about only by transient highly

reactive species generated in situ. Here we show that the oxidative addition of

the C–C bond in benzene by an isolated metal complex is not only possible,

but occurs at room temperature and reversibly at a single aluminium center in

[(NON)Al]− (where NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-

dimethylxanthene). Selectivity over C–H bond activation is achieved kinetically

and allows for the generation of functionalized acyclic products from benzene.

Abstract

C–C

Al C–C

C–H C–C

6

Hicks, J.; Vasko, P.; Goicoechea, J. M.; Aldridge, S.

Reversible, Room-Temperature C–C Bond Activation of Benzene by an Isolable Metal Complex.J. Am. Chem. Soc. 2019, 141, 11000-11003.

Prof. Jose GoicoecheaOxford UniversityPostdoc

w. Slavi C. Sevov (U Notre Dame)

Ph.D. in 2003

w. Michael K. Whittlesey@U of Bath

Graduated U de Zaragoza

Introduction: C-H(1) abstract(2) (review)

Ref 1Ref 2Ref 3 aromatic

Ref 4 1-3

Ref 5:

Ref 6: πRef 7:

Ref 8

Cp2WC-H

Ref 9: C-H

Introduction 2: C-CRef 10 Ref 14

Ref 11: Ref 10 (Nature )Ref 12

C-C

W

PMe3

Me3P

Me3P

PMe3

NC

CN

W

PMe3

CH2

PMe2Me3P

Me3P

PMe3

HN

N

QoxH

Ref 13

C-C

Si(II) C-C

Ref 15

P(I) C-C

Ref 16

Ru p-cymene C-C

Introduction 3: C-CRef 17

Cp′

Cp′

Cp′Ti

Ti

Ti

HH

HH

HH

H

1

40 °C, 36 h–H2

H

H

H

H H

H

2, quantitative

Ti TiTi

H H

H

H

CH3

H

H

H

H

Cp′

Cp′

Cp′

Ti(III)2Ti(IV) C-C

Ref 18

Pd(II)C-C

Ref 19

Ir(I) C-C

Ref 20

C-C( )

R

NjCH COjAlkI Aik DA)

2

Ref 21a

C-C (Rh(II) )

Ref 21b

C-C ( )

Ref 22

Si(II)C-C

Ref 23

Si(II)C-C= Buchner ring expansion

Introduction 4: Al

   

 

 

   

 

 

(i) K[N(SiMe3)2](ii) AlI3

KC8 (excess)

(NON)H2 [Al(NON)]2

[K{Al(NON)}]2

KC8 (1 equiv.)

(NON)AlI

O

tBu

tBu

NH

Dipp

NH

Dipp

O

tBu

tBu

N

Dipp

N

Dipp

Al I

O

tBu

tBu

N

Dipp

N

Dipp

Al O

tBu

tBu

N

Dipp

N

Dipp

Al

O

tBu

tBu

N

Dipp

N

Dipp

Al O

tBu

tBu

N

Dipp

N

Dipp

Al

K

K

Ref 24

 

 

 

(NON)AlMe

[K{Al(NON)}] 2

MeOTf or MeI

(NON)AlH

(Nacnac)MesMgAl(NON)

(NON)Al Al(NON)

(NON)AlI

HX / –KX

[K{H2Al(NON)}]2 (R = H)

H2 or C6H6

[K{Ph(H)Al(NON)}]2 (R = Ph)

(Nacnac)MesMgI(OEt2)

–KOTf or KI

O

tBu

tBu

N

Dipp

N

Dipp

Al H

O

tBu

tBu

N

Dipp

N

Dipp

Al O

tBu

tBu

N

Dipp

N

Dipp

Al

K

K

O

tBu

tBu

N

Dipp

N

Dipp

Al Me

O

tBu

tBu

N

Dipp

N

Dipp

Al MgH H

R

R

N

N

Mes

Mes

[e.g. (NON)H2

–K2(NON)]

Al

Ref 25

 

 

 

 

 

 

 

   

 

 

 

 

   

O

tBu

tBu

N

N

Dipp

Dipp

Al O

tBu

tBu

N

N

Dipp

Al

Dipp

K

K

O

tBu

tBu

N

N

Dipp

Dipp

Al Au PtBu3

1 3

tBu3PAuI– KI

  �     �  

 

     

   

   

   

   

 

 

 

 

       

     

 

 

 

   

 

 

 

 

 

O

tBu

tBu

N

N

Dipp

Dipp

AlE

E

iPrNCNiPror CO2

Au PtBu3

E = iPrN, 4E = O, 5

� �

Al CO2

AlAl-I

Al–Al

SN2

C–H, H–H

This Work 1: Al

Al–N 2.022(1) Å2.049(1) Å

Al–O 2.175(1) Å

Scheme 1. Sequestration of the Potassium Cations fromDimeric 1 To Generate Monomeric Aluminyl Compound[K(2.2.2-crypt)][(NON)Al], 2

Scheme 2. Room Temperature CC Bond Activation ofBenzene by 2 To Give Metallacycle 3; Facile Exchange ofthe C6H6 Fragment of 3 in the Presence of C6D6

Al–N 1.963(2) Å1.956(2) Å

Al–O 2.279(2) Å

Cf. 1 60 ℃, 96Al(H)(Ph)

dH 7.21, 7.00, 5.97 ppm Crystal structure of 3

Crystal structure of 2

Al–C 1.980(2) ÅC–C 1.343(2) Å

1.442(3) Å1.352(3) Å1.451(3) Å1.352(3) Å

Al

Temperature(°C) Rateconstant(k)

60 2.31x10–5

65 4.53x10–5

70 8.73x10–5

75 1.639x10–4

80 2.759x10–4

Al···Al Al···K(>7 Å)

3 C6D6 3Al1H NMR

Scheme 3. Reactions of 2 and 3 with Naphthalene at 80 °CTo Give a Mixture of CH Activation Products Resultingfrom Attack at the 1 and 2 Positions29

2 34a,4b →3

This Work 2:

Figure 2. DFT-calculated (DFT-D3, PBE0, Def-TZVP) pathways for benzene CC and CH bond activation by 2′. For computationalefficiency the backbone tBu groups of the NON ligand were replaced by methyl groups in all calculations. The “cut-down” versions of compounds2, 3 and 5 so modeled are labeled 2′, 3′ and 5′.

tBu Me

C–C 3’C–H 5’3’ TS 23 kJ/mol

3’

3’ 5’ 137 kJ/mol

→ 3 80 ℃5NON

DFT 2’ 3’ IntInt 2’ (1+2)→ 2

6 (C–C 1.598(2) Å)

6

5

Int 3’ 6π

Scheme 4. Generation of an Acyclic Product Containing acis, cis, cis Triene Fragment by the Reaction of 3 with a TinElectrophile

cis,cis,cis

Other Experiments and Next Approach

→

(= A E )

s- p- 2018(

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