effets de sel en chimie organique et organométalliqueicmub.u-bourgogne.fr/cours/jlacour_c_salt...

Effets de sel en chimie organique et organométallique

Prof. Jérôme Lacour, Organic Chemistry Department

Université de Dijon, ICMUB, 20.03.08

Salts Effects in Organic and Organometallic Chemistry

Introduction and General Aspects

Kinetic effects in catalysis

Thermodynamic effects insupramolecular chemistry

Structural characterization

Perspectives

Salts Effects in Organic and Organometallic Chemistry




Structural Characterization

Perspectives

The Various Types of Ion Pairs

A+ X-


A+ X-

ContactTight

Intimate

SS

SS

S

S

SS

SS

S

LooseSolvent Separated

A+ X-S


A+ X-

ContactTight

Intimate

A+ X-S


A+ X-

DISSOCIATION

S

SS

S

S


AGGREGATION

A+ X-

A+X-

A+ X-

A+X-

E E

+-

Penetrated

G. Boche, Angew. Chem., Int. Ed. Engl., 1992, 31, 731

A+ X-

ContactTight

Intimate

A+ X-S


1. Donor Solvents – DN scaleSolvents possessing a lone pair (Lewis base)Strongly solvating cations

2. Acceptor Solvents – AN scaleLewis acid solvents accepting lone pairsand therefore solvating strongly anions

Donor and Acceptor Solvents

Importance of Solvents

1. Polar Protic (εr > 15)Dissociated Ions

2. Apolar Aprotic (εr < 15, μ < 2.5 D)Strongly Associated IP or Aggregates

3. Polar Aprotic (εr > 15, μ > 2.5 D)Dissociated Ions or Weakly Associated

Protic and Aprotic /Polar or Apolar Solvents

S : A+DN

S X-AN

Electrostatic Modulation

Coulombic Interactions

qq’1

r4 π εr

Eint =

εr = dielectric constant of the mediumr = distance between the two chargesq et q’ = charges

Applied to Ion Pairs

1qq’

εr r4 πEass =

εr = dielectric constant of the mediumr = sum of the ionic radii of the solvated speciesq et q’ = charge on each of the ions

A+ X-Contact

TightIntimate

A+ X-S


High εrLow εr

Electrostatic Modulation

Minimum distance for nointeraction between two ions

εr = dielectric constant of the mediume = charge on the electronZ1, Z2 = Valence of the ionsk = Boltzmann constantT = absolute temperature (K)

Z1Z2e2

k T2 εr

dmin =

280

εr

dmin = (in Å at 25 °C)

A+ X-

H2O εr = 80 dmin = 3.6 Å Dissociated

DISSOCIATION

H2O

X-

C6H6 εr = 2 dmin = 140 Å IonicAssociation

A+Contact

TightIntimate

CIP

C6H6

dmin

« HSAB Symbiotic Effect »

H+ > Li+ > Na+ > K+ > Rb+ > Cs+

F- > Cl- > Br- > I-

Ph4As+ > Ph3C+ >> R4N+ > K+ > Na+ > Li+

Ph4B- > Ph3C- >> I- > Br- > Cl- > F-

A+

X-

« Hard » Ions

High charge density

Not bulkyLocalized chargeLow polarizability

A+

X-

« Soft » Ions

Low charge density

BulkyOften of delocalized chargeUsually Polarizable

A+ X- A+ X-

Pearson, R. G. J. Am. Chem. Soc. 1963, 85, 3533

« HSAB Symbiotic Effect »

Hard anions – Low HOMOsHard cations – Very high LUMOs

Interaction under Charge Control

The interaction between a hard cation and a hard anion or betweentwo soft ions is stronger than that between two ions of different type

A+

X-

« Hard » Ions

H+ > Li+ > Na+ > K+ > Rb+ > Cs+

F- > Cl- > Br- > I-

Soft anions – Very high HOMOsSoft cations – Low LUMOs

Interaction under Orbital Control

A+

X-

« Soft » Ions

Ph4As+ > Ph3C+ >> R4N+ > K+ > Na+ > Li+

Ph4B- > Ph3C- >> I- > Br- > Cl- > F-

Salts Effects in Organic and Inorganic Chemistry





Perspectives

Evans et al. Angew. Chem. Int. Ed. Engl. 1995, 34, 768

Diels-Alder Reactions

Evans et al. Angew. Chem. Int. Ed. Engl. 1995, 34, 768


Note: temperature or anion effect ?

OTfSbF6OTfSbF6

ee 87% ~ rapport 14.4:1; ee 96% ~ rapport 49:1


SbF6- TfO-


Angew. Chem. Int. Ed. 1999, 38, 1220

CF3

CF3 4

B

BArF


3 CH···F interactions

Angew. Chem. Int. Ed. 1999, 38, 1220

Carbo and Hetero Diels-Alder Reactions

J. Chem. Soc., Perkin Trans. 2 1997, 1183

Carbo and Hetero Diels-Alder Reactions

DN ANDCM - 20.4MeNO2 2.7 20.5DMF 26.6 16.0

MeCN 14.1 18.9

THF 20.0 8.0

MeNO2 εr 35.9 CH2Cl2 εr 8.9

J. Chem. Soc., Perkin Trans. 2 1997, 1183

Angew. Chem. Int. Ed. 1998, 37, 2897

CF3

CF3 4

B

Moisture!

TOF: 1a 41 min-1 while 1e 70-135 min-1

Hydrovinylation Reactions

J. A. Chem. Soc. 1999, 121, 9899

ethylene (1 atm)0.35 mol% [(allyl)Ni-Br]2

Ph3P, AgOTf

Chem. Eur. J. 1999, 5, 1963.


R3P*, AgOTf∗

MeO MeO

PPh2

O

R = OMe, OBn

R


J. A. Chem. Soc. 1999, 121, 9899


R3P, AgOTf


R3P*, NaBARF∗

MeO MeO

Chem. Eur. J. 1999, 5, 1963.

PPh2

O

R = OMe, OBn

R

No rxn with NaBARF

BARF


J. A. Chem. Soc. 1999, 121, 9899


R3P, AgX

P

Me

MeX

5a H

5b OCH2Ph

5c CH2OCH2Ph

5d CH2OCH3

X


J. Am. Chem. Soc. 1999, 121, 9899

H2C

XNi

H2C

HC

P

Ar

X = OTf, ClO4

H2C

X

NiH2C

HC

P

Ar

X = SbF6, BARF

5a

See also D. Voigt J. Organomet. Chem. 1998, 552, 187

H2C

ONi

H2C

HC

P

Ar

R

H2C

XNi

H2C

HC

P

Ar

RO

X = OTf, ClO4X = SbF6, BARF

5c

P

Me

MeX

5a H

5b OCH2Ph

5c CH2OCH2Ph

5d CH2OCH3

X






Perspectives

Cation-π interactions

NR

Host-Guest Chemistry

Böhmer, Collet, Ito, Kubik, Rebek, Sanders, Shinkai, etc.

A+X-

?

Initial Results

N 9

From chloride to iodide x 19 decrease

Quite bizarre

Tetrahedron Lett. 1998, 39, 3779

More complete stories

J. Am. Chem. Soc. 1999, 121, 11908J. Am. Chem. Soc. 2002, 124, 8307

Picrate > trifluoroacetate > I- >Br- > Cl- > tosylate > acetate

NO2

NO2O2NO

Explanation?


Explanation?


Ion pair dissociation energy

Guest appears to respond to the cation’s chargedensity exposed to the receptor, which is determinedby the anion’s charge density through a polarizationscheme

Not so simple, see Hunter Chem. Commun. 2003, 834

Beware – The whole ion pair may need to be considered

2 3

Δ-4 Λ-4






Perspectives

A+ X-

?

nOe and PGSEexperiments

NOEs and PGSE experiments

For organic compounds, see Pochapsky Magn. Reson. Chem. 2000, 38, 90 and incl. ref.

NOEs and PGSE experiments - Reviews

Qualitative NMR Investigations

Review : Euro. J. Inorg. Chem. 2003, 195

19F, 1H HOESY


1H NOESY

Review : Euro. J. Inorg. Chem. 2003, 195


R = H, R’’ = Me

R = i-Pr, R’’ = Me

Organometallics 1999, 18, 4367

X-

X-



decreasing NOEsTfO- > BF4

- > PF6 - > BARF

For a recent account, see Chem.Eur. J. 2007, 13, 1570

Quantitative NMR Investigations


From qualitative to quantitative information ?

Quantitative NMR Investigations


Quantitative experiments – Diffusion Coefficients

Helv. Chim. Acta 2001, 84, 3833

CIP


Helv. Chim. Acta 2001, 84, 3833

CIP

SSIP


Ar = pTol, R = tBu

Chem. Commun. 2002, 286

Solvent CD2Cl2

anion

cation


Chem. Commun. 2002, 286

No strong ion-pairing in methylene chlorideAr = pTol, R = tBu

PGSE and aggregation studies

excess of MX- 2 MCl

Aggregation increases with non-coordinating anions such as BPh4−

PGSE and aggregation studies

excess of MX- 2 MCl

CD2Cl2






Perspectives

Towards Real Non-Coordinating Anions

Chem. Eur. J. 2002, 8, 2088

Towards Real Non-Coordinating Anions

Chem. Eur. J. 2002, 8, 2088

PPh3

(PPh3)2

Just a beautiful picture ?

Angew. Chem. 2003, 115, 3611

19F NMR δ –26 ppmAnhydrous [TBA][F] δ –73 ppm

Chiral counterions

Chiral counterions

PPh3 conv. 39% ee 64%P(o-tolyl)3 conv. 35% ee 74%

Chiral counterions

See also JACS 2006, 128, 13368

Chiral counterions

Acknowledgments

Merci pour votre attention

Martina AUSTERI; Renaud BACH; Rémy BERNARD; Frédéric BURON; Samuel CONSTANT; ValérieDESVERGNES-BREUIL; France FAVARGER; Richard FRANTZ; Helena GONCALVES-FARBOS; Catherine GOUJON-GINGLINGER; Stéphane GRASS; Virginie HEBBE-VITON; Christelle HERSE; Jonathan JODRY; Benoit LALEU; Nathalie L’HELIAS; David LINDER; Anne LONDEZ; Claire MARSOL; Alexandre MARTINEZ; Nathalie MEHANNA; Christophe MICHON; Pierre MOBIAN; David MONCHAUD; Jessica MULLER, Cyril NICOLAS; Roman NOVIKOV; Céline PEROLLIER; Dalit RECHAVI; Ankit SHARMA; Franck TORRICELLI; Simone TORTOIOLI; Jerome VACHON; Laurent VIAL; Walid ZEGHIDA

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