Thesis Talk

40
Structural and Mechanistic Aspects of Copper Catalyzed Atom Transfer Radical Addition Reactions in the Presence of Reducing Agents William T. Eckenhoff and Tomislav Pintauer Department of Chemistry and Biochemistry Duquesne University Pittsburgh, PA 15282 1 Thesis Defense

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Transcript of Thesis Talk

Page 1: Thesis Talk

Structural and Mechanistic Aspects of Copper Catalyzed Atom Transfer Radical

Addition Reactions in the Presence of Reducing Agents

William T. Eckenhoff and Tomislav PintauerDepartment of Chemistry and Biochemistry

Duquesne UniversityPittsburgh, PA 15282

1Thesis Defense

Page 2: Thesis Talk

Kharasch Addition Reaction

• Free Radical Mechanism• Initiated by light or radical

initiators (e.g. AIBN)PRINCIPLE PROBLEMS:

- Unavoidable radical-radical termination reactions (kt≈1.0×109 M-1s-1)

- Repeating radical addition to alkene to generate oligomers/polymers

- Low chain transfer constant (ktr/kp)

SOLUTIONS:- Search for better halogen

transfer agents (transition metal complexes)

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Initiation:

Propagation:

Termination:

+ Br3C Brki + CBr3

+kadd Br3C

R

kp

RR Br3C

R

Rn

Br3CR +

ktrBr3C

R

Br

+

radical-radical coupling

+kt

Br3C CBr3

+kt

Br3CR + Br3C

R

kt

etc.

Br3C

monoadduct

R

CBr3R

AIBNΔ

CN+ N2

CN CN

Br

CBr3

Br3C Br CBr3

CBr3 CBr3

CN CN CN

CN

Kharasch, M. S.; Jensen, E. V.; Urry, W. H. Science 1945, 102, 128.

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Transition Metal Catalyzed (TMC) ATRA

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• Transition metal complexes of Fe, Ru, Co, Ni and Cu are particularly effective halogen transfer agents.

• Variety of alkenes and alkyl halides can be utilized.

TO ACHIEVE HIGH YIELDS:- Radical concentration must be

low (ka,1 and ka,2<<kd,1 and kd,2)- Further activation of the

monoadduct should be avoided (ka,1>>ka,2 and ka,2≈0)

- The formation of oligomers/polymers should be suppressed (kd,2[CuIILmX]>>kp[alkene])

Minisci, F. Acc. Chem. Rec. 1975, 8, 165.Clark, A. J. Chem. Soc. Rev. 2002, 31, 1.Severin, K. Curr. Org. Chem. 2006, 10, 217.

kp

RR'

R'n

L=complexing ligandX=halide or pseudo halide

CuIILmX2

CuILmX

R

R X

R'R

kadd

R'

R'

XR

R kt

R R

ka,1

kd,1

ka,2

kd,2

R'

R kt

R'R

R

etc.

K1=ka,1kd,1

K2=ka,2kd,2

kd,1 kd,2

ka,1 ka,2

Page 4: Thesis Talk

TMC ATRA in Organic Synthesis• Can be conducted intermolecularly and intramolecularly.• Atom transfer radical cyclization (ATRC) is a particularly

attractive tool because it enables synthesis of functionalized ring systems.

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CCl3

OO

CH3CN, 110 oC

CuCl (30 mol%)O

ClClCl

O

95% yield16 h

CCl3

NO

CH3CN, RT

CuCl/bpy (5 mol%)15 min

SO3CH3SO3CH3

N

ClClCl

O

91% yield

O O

OEtCl Cl

DCE, 80 oC

CuCl/bpy (25 mol%)18 h

O O

OEtCl

Cl61% yield

H

Clark, A. J. Chem. Soc. Rev. 2002, 31, 1.Yang, D.; Yan, Y. -L.; Zheng, B. -F.; Gao, Q.; Zhu, N.-Y. Org. Lett. 2006, 8, 5757.

γ-lactones and γ-lactams

Cascade TMC ATRA

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TMC ATRA is not Widely Used in Organic Synthesis

5SciFinder Scholar Search as of February 1, 2010

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Current Drawbacks of TMC ATRA

• TMC ATRA despite being discovered nearly 20 years before tin mediated radical addition to olefins and iodine atom transfer radical addition is still not fully utilized as technique in organic synthesis.

• The principal reason is that TMC ATRA typically requires between 5 and 30 mol% of catalyst relative to alkene.

• Problems in product separation and catalyst recycling.• Process is environmentally unfriendly and expensive.

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Methodologies developed to overcome these drawbacks: Design of solid supported catalysts Use of biphasic systems (fluorous solvents) Development of highly active complexes based on ligand

design Catalyst regeneration in the presence of reducing

agents✓Clark, A. J. Chem. Soc. Rev. 2002, 31, 1.

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Catalyst Regeneration in the Presence of Reducing Agents

Eckenhoff, W. T.; Pintauer, T. Cat. Rev. - Sci. Eng. 2010, 51, 1-59.Ricardo, C.; Pintauer, T. Chem. Comm. 2009, 21, 3029-3031.Pintauer, T.; Matyjaszewski, K. Chem. Soc. Rev. 2008, 37, 1087.Eckenhoff, W. T.; Garrity, S. T.; Pintauer, T. Eur. J. Inorg. Chem. 2008, 563.Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2007, 46, 5844.Quebatte, L.; Thommes, K.; Severin, K. J. Am. Chem. Soc. 2006, 128, 7440.Matyjaszewski, K.; Jakubowski, W.; Min, K.; Tang, W.; Huang, J.; Braunecker, W. A.; Tsarevsky, N. V. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 15309.

AIBN

N2

CN

X

CN Δ

+ R X + Rka,1

kd,1

R R

kt

MtnLm Mtn+1LmX • Originally developed for atom transfer radical polymerization (ATRP).

• Successfully applied to ATRA catalyzed by copper(II) and ruthenium(III) complexes.

• The rate of alkene consumption in ATRA depends on the ratio of concentrations of activator (CuI) and deactivator (CuII-X):

• Deactivator accumulates during the process as a result of radical termination reactions.

• Reducing agents can be used to regenerate activator.

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−d[M]dt

= kadd[M][R•] =kaddKATRA[M][RX][CuI]

[CuII − X]

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TMC-ATRA in the Presence of Reducing Agents

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ATRA Catalyzed by CuI(TPMA)Cl Complex in the Presence of Reducing Agent AIBN

• Can be conducted using either copper(I) or copper(II) complex.• TONs for 1-octene (4350-6700) and 1-hexene (4900-7200) highest so far for copper

mediated ATRA.• Previous TONs ranged between 0.1 and 10!

9Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2007, 46, 5844.

Entry Alkene RCl [Alkene]0/[CuI]0 Yield (%) TON

1 2 3 4 5 6 7 8 9 10 11 1 2

1-hexene 1-octene styrene methyl acrylate 1-hexene 1-octene styrene methyl acrylate

CCl4

CCl4

CCl4

CCl4 CHCl3

CHCl3

CHCl3

CHCl3

10000:1 5000:1 10000:1 5000:1 1000:1 500:1 250:1 1000:1 1000:1 500:1 1000:1 1000:1

72 98 67 87 42 54 85 60 56 49 58 6 3

7200 4900 6700 4350 420 270 212 600 560 245 580 630

TPMA

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• Highest TONs for copper mediated ATRA

• Highly efficient ATRA in the presence of 5-100 ppm of copper

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ATRA Catalyzed by [CuII(TPMA)Br][Br] Complex in the Presence of Reducing Agent AIBN

Entry Alkene RBr [Alkene]0:[CuII]0 Yield (%) TON1 methyl acrylate CBr4 / 32 /2 200,000:1 81(76) 1.6×105

3 100,000:1 94 9.4×104

4 styrene CBr4 / 72 /5 200,000:1 95(86) 1.9×105

6 100,000:1 99 9.9×104

7 methyl acrylate CHBr3 1,000:1 57 5.7×102

8 500:1 66 3.3×102

9 styrene CHBr3 10,000:1 70 7.0×103

10 5,000:1 77 3.9×103

11 1,000:1 92 9.2×102

12 1-hexene CHBr3 10,000:1 61(59) 6.1×103

13 1-octene CHBr3 10,000:1 69(54) 6.9×103

14 1-decene CHBr3 10,000:1 63(64) 6.3×103

Eckenhoff, W. T.; Garrity, S. T.; Pintauer, T. Eur. J. Inorg. Chem. 2008, 563.

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Copper Catalyzed ATRA of Highly Active Alkenes

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• Alkenes with high propagation rate constants in free radical polymerization require large catalyst loadings.

• Competing radical polymerization initiated by AIBN at elevated temperatures.

• Solution is to utilize redox reducing agents (ascorbic acid, glucose, magnesium, etc.) or low temperature free radical initiators such as V-70

Pintauer, T.; Eckenhoff, W.T.; Balili, M. N. C.; Biernesser, A. B.; Noonan, S. J.; Ricardo, C.; Taylor, M. J. W. Chem. Eur. J. 2009, 15, 38.Beuermann, S.; Buback, M. Prog. Poly. Sci. 2002, 27, 191-254

Alkenekp (M-1 s-1)

60oC 25oC

2.8x104 1.3x104

3.1x104 1.5x104

7.9x103 3.4x103

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Highly Efficient Ambient Temperature ATRA in the Presence of V-70 as a Reducing Agent

12Pintauer, T.; Eckenhoff, W.T.; Balili, M. N. C.; Biernesser, A. B.; Noonan, S. J.; Ricardo, C.; Taylor, M. J. W. Chem. Eur. J. 2009, 15, 38.

• For simple α-olefins, efficient ATRA was achieved using as little as 0.002 mol% of [CuII(TPMA)X][X] complexes (20 ppm!!!).

• Reactions were also very efficient for methyl acrylate, methyl methacrylate and vinyl acetate.

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Structural Features of CuI(TPMA)Cl and [CuII(TPMA)Cl][Cl] Complexes

• Copper(I) and copper(II) complexes are structurally similar.13

CuI(TPMA)Cl [CuII(TPMA)Cl][Cl]

Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2007, 46, 5844.

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Structural Features of CuI(TPMA)Br and [CuII(TPMA)Br][Br] Complexes

• Copper(I) and copper(II) complexes are structurally similar.

CuI(TPMA)Br [CuII(TPMA)Br][Br]

Eckenhoff, W. T.; Garrity, S. T.; Pintauer, T. Eur. J. Inorg. Chem. 2008, 563.

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Questions about ATRA Mechanism

MtnLm Mtn+1Lm + eKET

X + eKEA

X

R-X R + X

X + Mtn+1Lm Mtn+1LmX

KBH

KHP

MtnLm + RX Mtn+1LmX + RKATRA

Electron Transfer

Electron Affinity

Bond Homolysis

Halidophilicity

For a given alkyl halide KATRA will depend on

KET and KHP

KATRA=KEAKBHKHPKET

KATRAKEAKBH

= KETKHP

• The role of halide anion coordination to [CuI(TPMA)]+ remains unclear.

• Nature of ATRA (ISET or OSET)?

• Equilibrium constant for ATRA can be expressed in terms of:

Lin, C.Y.; Coote, M.L.; Gennaro, A.; Matyjaszewski, K. J. Am. Chem. Soc. 2008, 130(38), 12762-12774

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Correlating Redox Potential with Catalyst Activity

E1/2 / mV v.s. SCE0 -50 -100 -150 -200 -250 -300 -350 -400 -450 -500

N N

RR

N N R

N

N

N

NN

N

R

R RN

NNN

N

N

NN

N

N N

N

More Reducing CuIBr ComplexesHigher Activity in ATRA

Qiu, J.; Matyjaszewski, K.; Thouin, L.; Amatore, C. Macromol. Chem. Phys. 2000, 201, 1625-1631.

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Cyclic Voltammetry of [CuI(TPMA)][A] Complexes

• Coordination of bromide anion to [CuI(TPMA)]+ results in a formation of much more reducing CuI(TPMA)Br complex.

• Based on CV (KATRA), CuI(TPMA)Br complex should be a MILLION times more active in ATRA.

Complex Supp. Elect. E1/2 /mV ΔEp / mV ipa/ipc

[CuI(TPMA)][BPh4] TBA-BPh4 -397 107 1.17

TBA-Br -699 109 0.94

[CuI(TPMA)][ClO4] TBA-ClO4 -422 94 0.95

TBA-Br -706 97 0.92

[CuI(TPMA)][PF6] TBA-PF6 -421 88 0.94

TBA-Br -711 88 0.91

CuI(TPMA)Br TBA-Br -720 93 1.08

CuI(TPMA)Cl TBA-Cl -742 111 1.16

Potentials are reported vs. Fc/Fc+.

Eckenhoff, W. T.; Pintauer, T. unpublished resultsEckenhoff, W. T.; Garrity, S. T.; Pintauer, T. Eur. J. Inorg. Chem. 2008, 563.

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Cyclic Voltammetry of [CuI(TPMA)][A] Complexes

18Eckenhoff, W. T.; Pintauer, T. unpublished results

• TBA-Br was titrated into a solution of [CuI(TPMA)BPh4] and was observed to quantitatively displace BPh4 from copper(I) complex.

• Explains effect of supporting salt on E1/2 on [CuI(TPMA)X] complexes.

• Displays strongly affinity of Br- to Cu(I).

Eckenhoff, W. T.; Pintauer, T. unpublished results 30

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Conductivity of Copper Complexes

• Conductance of copper(I) species reflect degree of ionic character.

• Complexes with halide anions were found to have less conductivity than those with non-coordination counter-ions.

• Suggests association in solution19

Complex Conductivity (µS)CuI(TPMA)Cl 2.64(±0.01)CuI(TPMA)Br 3.01(±0.02)

CuI(TPMA)ClO4 5.50(±0.05)CuI(TPMA)BPh4 6.29(±0.02)CuI(TPMA)PF6 6.39(±0.11)

Eckenhoff, W. T.; Pintauer, T. unpublished results

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Catalytic Performance of [CuII(TPMA)][A] Complexes in ATRA

• The counter-ion appears to have little or no effect on catalytic performance in ATRA in the presence of AIBN.

• Does the counter-ion effect the rate of alkene consumption?20

Complex R-X Alkene Alkene:Catalyst Conversion Selectivity Yield

[Cu(TPMA)Cl][Cl] CCl4 Hexene 5000:1 100% 100% 100%[Cu(TPMA)Cl][ClO4] 100% 100% 100%

[Cu(TPMA)Cl][PF6] 100% 100% 100%

[Cu(TPMA)Cl][BPh4] 100% 100% 100%

[Cu(TPMA)Cl][Cl] CCl4 Octene 5000:1 99% 100% 99%

[Cu(TPMA)Cl][ClO4] 99% 100% 99%

[Cu(TPMA)Cl][PF6] 99% 100% 99%

[Cu(TPMA)Cl][BPh4] 95% 100% 95%

[Cu(TPMA)Cl][Cl] CCl4 Styrene 1000:1 76% 59% 45%

[Cu(TPMA)Cl][ClO4] 83% 60% 50%

[Cu(TPMA)Cl][PF6] 81% 60% 49%

[Cu(TPMA)Cl][BPh4] 79% 59% 47%

[Cu(TPMA)Cl][Cl] CCl4 Methyl Acylate 1000:1 100% 45% 45%

[Cu(TPMA)Cl][ClO4] 100% 48% 48%

[Cu(TPMA)Cl][PF6] 100% 48% 48%

[Cu(TPMA)Cl][BPh4] 100% 44% 44%Reactions performed at 60oC in CH3CN, [alkene]0:[R-X]0:[AIBN]0=1:1:0.05, [alkene]0=2.10 M. Conv., Prod., and Yields determined by 1H NMR

Eckenhoff, W. T.; Pintauer, T. unpublished results

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Catalytic Performance of [CuII(TPMA)X][Y] Complexes in ATRA with AIBN

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[1-Oct]0:[CCl4]0:[AIBN]0:[CuII]0=5000:5000:250:1 • Rate of consumption of alkene is independent on counter-ion.

• Rate should depend only on AIBN concentration.

• However, product distribution (particularly for highly active alkenes) MUST depend on catalyst nature (ka and kd)

kp[alkene]kd[CuII]

Controls the product yield

RX + CuILXka

kdR + CuIILX2

Eckenhoff, W. T.; Pintauer, T. unpublished results

Reactions performed at 60oC in CH3CN, [alkene]0:[CCl4]0:[AIBN]0 =1:1:0.05, [alkene]0=2.10 M. Conv. determined by 1H NMR

Page 22: Thesis Talk

Catalytic Performance of [CuI(TPMA)Y] Complexes in ATRA without AIBN

• Using 50:1 alkene to copper ratio, without AIBN present, complexes with non-coordinating counter-ions were more active

22Eckenhoff, W. T.; Pintauer, T. unpublished results

Reactions performed at 60oC in CH3CN, [alkene]0:[CCl4]0 =1:1, [alkene]0=2.10 M. Conv. determined by 1H NMR

[MA]0:[CCl4]0:[Cu]0=50:50:1

Complex KATRA (10-7)

[CuI(TPMA)Cl] 2.21(±0.07)

[CuI(TPMA)ClO4] 4.65 (±0.03)

[CuI(TPMA)BPh4] 4.48 (±0.07)

Page 23: Thesis Talk

Structural Features of CuI(TPMA)Br in Solution

• Low T 1H NMR consistent with X-ray structure.

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1H NMR400 MHz, (CD3)2CO

Proton Δδ / ppmH1 0.60H2 0.12H3 0.05H4 -0.32H5 0.10

• Broadening of the spectra is induced by fluxional processes:

• Dimer formation unlikely (inequivalent methylene protons).

1. TPMA dissociation 2. Br- dissociation

Eckenhoff, W. T.; Garrity, S. T.; Pintauer, T. Eur. J. Inorg. Chem. 2008, 563.

Page 24: Thesis Talk

Solution Equilibria for CuI(TPMA)X Complexes

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Possible Reasons for TPMA Fluxionality1. Halide dissociation2. TPMA arm dissociation

298 K

Eckenhoff, W. T.; Pintauer, T. Unpublished results

• Addition of TBA-Br results TPMA signals shifting towards free ligand.

• Binding of TPMA is probably in equilibrium driven to the uncomplexed form.

Page 25: Thesis Talk

Structural Features of [CuI(TPMA)(CH3CN)][BPh4]

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Similar to CuI(TPMA)XCu1-N1=2.430(6) ÅCu1-N2=2.069(6) ÅCu1-N3=2.077(6) ÅCu1-N4=2.122(6) ÅCu1-N5=1.990(6) Å

Axial elongationof Cu-N bond

Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2010, 49(22), 10617-10626

Page 26: Thesis Talk

• First example of a dimer where one arm of TPMA ligand coordinates to the second metal center

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Structural Features of [CuI(TPMA)]2[ClO4]2

Distorted TetrahedralCu1-N1=2.2590(13) ÅCu1-N2=1.9909(12) ÅCu1-N3=2.2213(16) ÅCu1-N4=1.9593(13) Å

1H NMR (400 MHz, (CD3)2CO)

Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2010, 49(22), 10617-10626 Eckenhoff, W. T.; Pintauer, T. Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 2008, 49(2), 282.

Page 27: Thesis Talk

Structural Features of [CuI(TPMA)(CH3CN)][BPh4]

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90% Monomeric10% Dimeric

[CuI(TPMA)]2[ClO4]2

[CuI(TPMA)BPh4]

180 K

[CuI(TPMA)][BPh4]

Trigonal PyramidalCu1-N1=2.211(3) Å

Cu1-Cu2=2.832(5) Å

1H NMR (400 MHz, (CD3)2CO)

Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2010, 49(22), 10617-10626

Page 28: Thesis Talk

Structural Features of [(CuI(TPMA))-µBr][BPh4]

• Originated from attempted synthesis of [CuI(TPMA)BPh4] by salt metathesis with [CuI(TPMA)Br]

• Shows another motif of copper(I) stabilization not previously considered

• Also indicates strong preference for halide binding

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Bimetallic Distorted TetrahedralCu1-N1=2.429(2) ÅCu1-N2=2.067(2) ÅCu1-N3=2.131(2) ÅCu1-N4=2.065(2) Å

Cu1-Br1=2.5228(4) ÅEckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2010, 49(22), 10617-10626

Page 29: Thesis Talk

1H NMR of CuI(TPMA)Br with Excess TPMA

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1H NMR (400 MHz)(CD3)2CO

CuI(TPMA)Br + TPMA* CuI(TPMA)*Br + TPMAK

-3

-2

-1

0

1

2

3

4

0.0035 0.004 0.0045 0.005 0.0055

ln(k/T)

1/T(K)

Eckenhoff, W. T.; Pintauer, T. Unpublished results

ΔH‡=2.96 KJΔS‡=-60 J K-1

ΔG‡=43.25 KJ (10.3 kcal)

Page 30: Thesis Talk

TPMA Arm Dissociation from Copper(I) Center

• Large coordinating ligands can displace single arm of TPMA.• Also demonstrated previously with 1,4-diisocyanobenzene.

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Molecular Structure of [CuI(TPMA)2(4,4’-dipyridyl)][BPh4]2

Cu-Nax 2.325 ÅCu-Neq 2.085, 2.052 ÅCu-Ndis 2.523 ÅCu-Ndp 1.998 Å

Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2010, 49(22), 10617-10626Hsu, S.C.; Chien, S.S.; Chen, H.H.; Chiang, M.Y. J. Chin. Chem. Soc. 2007, 54(3), 685-692

Page 31: Thesis Talk

ATRA Inhibition with PPh3

• PPh3 bonds strongly to copper, displacing a pyridyl arm

• Tetrahedral geometry• Oxidatively stable in air• Pyridine signals shifted upfield from

PPh3 donation/weaker Py coordination• 31P NMR shows downfield shift

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Molecular Structure of [CuI(TPMA)2PPh3][BPh4]2

Cu-Nax 2.214 ÅCu-Neq 2.073, 2.114ÅCu-Ndis 3.327 ÅCu-P 2.1853 Å

Eckenhoff, W. T.; Pintauer, T. Inorg. Chem. 2010, 49(22), 10617-10626

Tyeklar, Z.; Jacobson, R. R.; Wei, N.; Murthy, N. N.; Zubieta, J.; Karlin, K. D.J. Am. Chem. Soc. 1993, 115, 2677-2689.

-N-CH2-BPh4

BPh4

BPh4

Py -CH

Py -CH+ PPh3

PPh3

Py -CH

Page 32: Thesis Talk

ATRA Inhibition with PPh3

• Addition of more than stoichiometric quantities of PPh3 inhibited ATRA, but small amounts had little effect

• Rate decreased by a factor of 10, almost completely stopped with 20 eq. of PPh3 with the [Cu(TPMA)Cl][Cl] catalyst

• Similar effect found with P-(OBu)4

32Eckenhoff, W. T.; Pintauer, T. unpublished results

Reactions performed at 60oC in CH3CN, [alkene]0:[R-X]0:[AIBN]0=1:1:0.05, [alkene]0=2.21 M. Yields determined by 1H NMR

Alkene R-X Alk./Cat. 0 Eq. PPh3 20 Eq. PPh3 40 Eq. PPh3

1-Hexene CCl4 5000:1 100% 95% 78%1-Octene CCl4 5000:1 100% 76% 22%

Styrene CCl4 1000:1 26% 0%Methyl Acrylate CCl4 1000:1 44% 28%

Page 33: Thesis Talk

ATRA in the presence of PPh3

• ATRA catalyzed by [Cu(TPMA)PPh3][BPh4] proceeds similarly to [Cu(TPMA)Cl][Cl].

• R-X homolytic cleavage might occur through PPh3 dissociation or partial TPMA dissociation

• Large excesses of PPh3 can cause total TPMA displacement, producing a complex that is ATRA inactive

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Cu-P1: 2.3199(15) Å Cu-P2: 2.3169(15) ÅCu-P3: 2.3086(15) ÅCu-P4: 3.9551(17) Å

Cu-P1: 2.3150(5) ÅCu-P2: 2.3362(5) ÅCu-P3: 2.3147(5) ÅCu-N1: 2.1010(17) Å

[CuI(PPh3)(PPh3)][BPh4] [CuI(PPh3)3CH3CN][ClO4]

Eckenhoff, W. T.; Pintauer, T. unpublished results

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Copper complexes with TDAPA Ligand

• Very similar ligand structure to highly active ligands

• Coordinates to copper similarly

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[CuII(TDAPA)X][Y] Performance in ATRA

• Copper Complexes with the TDAPA ligand showed very little ATRA activity

• Ligand dissociation should be much slower as compared to TPMA

• Slight counter-ion effect observed

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Alkene Anion Yield1-hexene Cl- 24%1-octene 25%1-hexene BPh4- 60%1-octene 45%1-hexene BF4- 55%1-octene 59%

[Alkene]0:[CCl4]0:[AIBN]0:[CuII]0=250:250:12.5:1

Reactions performed at 60oC in CH3CN, [alkene]0=2.39 M. Yields determined by 1H NMR

Eckenhoff, W. T.; Pintauer, T. unpublished results

Page 36: Thesis Talk

Conclusions• Synthesis, characterization and exceptional activity of [CuII

(TPMA)X][X] (X=Br- and Cl-) complexes in ATRA of polyhalogenated compounds to alkenes in the presence of reducing agent AIBN was presented.

• [CuII(TPMA)Br][Br] in conjunction with AIBN effectively catalyzed ATRA of CBr4 and CHBr3 to alkenes with concentrations between 5 and 100 ppm, which is the lowest number achieved in copper mediated ATRA.

• Structural and mechanistic studies indicate that partial TPMA dissociation may be required for ATRA.

• The rate of alkene consumption was found to depend only on the AIBN concentration.

• In the absence of AIBN, copper(I) complexes with non-coordinating counter-ions were found to proceed faster than the corresponding chloride analogues.

36

Page 37: Thesis Talk

• Advisor: • Dr. Pintauer

• Duquesne University Committee members: • Dr. Basu• Dr. Fleming

• Outside Reader: • Dr. Matyjaszewski

• My Family: • Dana Eckenhoff• Parents - Drs Roderic and Maryellen Eckenhoff

37

Acknowledgments

Page 38: Thesis Talk

Graduate Students

• Dr. Marielle Balili• Carolynne Ricardo• April Hill• Raj Kaur• Merton Pajibo

38

AcknowledgmentsUndergraduate Students

• Sean Noonan• Matthew Taylor• Ashley Biernesser• Tom Ribelli

Page 39: Thesis Talk

Acknowledgments

Special Thanks to:

• The Bayer School Instrumentation Staff

• Dan Bodnar

• Dave Hardesty

• Lance Crosby

• Ian Welsh

• Sandy Russell, Amy Stroyne, Heather Costello

Page 40: Thesis Talk

Acknowledgments

Funding

• NSF Career Award (CHE-0844131)

• Duquesne University Start-up Grant

• NSF X-ray Facility Grant (CRIF-0234872)

• NSF NMR Grant (CHE-0614785)

40

Thank You!