![Page 1: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/1.jpg)
The Chemistry of Frustrated Lewis Pairs
MacMillan Group Meeting
4 December 2013
Tracy Liu
![Page 2: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/2.jpg)
B
RR
R
NR
RR
![Page 3: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/3.jpg)
B
RR
R
NR
RR
![Page 4: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/4.jpg)
B
RR
R
NR
RR B N
R
RR R
RR
![Page 5: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/5.jpg)
BRR
RNR
RR B N
R
RR R
RR
BRR
RNR
RR B N
R
RR R
RR
H2H H
![Page 6: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/6.jpg)
BRR
RNR
RR B N
R
RR R
RR
BRR
RNR
RR B N
R
RR R
RR
H2H H
heat
![Page 7: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/7.jpg)
0
20
40
60
80
100
2000 2006 2009 2012
Num
ber
of P
ublic
atio
ns
■ 289 total publications in FLP chemistry
■ Leading Academics:Douglas W. Stephan, University of Toronto, CanadaGerhard Erker, Westfälische Wilhelms-Universität Münster, GermanyImre Pápai, Chemical Research Cent. of the Hungarian Acad. of Sciences, Hungary
Rapid Emergence of FLP Chemistry
![Page 8: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/8.jpg)
N
Me
Me
BF3 BMe3No ReactionN
Me
Me
BF3
Brown, H. C.; Schlesinger, H. I. JACS, 1942, 64, 325-329.
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
![Page 9: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/9.jpg)
N
Me
Me
BF3 BMe3No ReactionN
Me
Me
BF3
Brown, H. C.; Schlesinger, H. I. JACS, 1942, 64, 325-329.
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
![Page 10: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/10.jpg)
Wittig, G.; Benz, E. Chem. Ber., 1959, 92, 1999-2013.
F
Br
Mg
PPh3BPh3
PPh3
BPh3
No formation of classical Lewis Acid/Base adduct
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
![Page 11: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/11.jpg)
Tochtermann, W. ACIE, 1966, 5, 351-371.
[Ph3C-]Na+
BPh3
Ph3C
BPh3
and Ph3C BPh3
no observation of polybutadiene
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C-
and BPh3 trap across olefins;coining of the term "FLP"
![Page 12: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/12.jpg)
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C-
and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"
PH
Me
Me
Me
2
+
FF
FF
B(C6F5)2(Me3C6H2)2PF
H
FF
FF
B(C6F5)2(Me3C6H2)2PH
H
B(C6F5)3
Me2SiHCl
Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D. W. Science, 2006, 314, 1124-1126.
![Page 13: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/13.jpg)
Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D. W. Science, 2006, 314, 1124-1126.
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C-
and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"
FF
FF
B(C6F5)2(Me3C6H2)2PH
H
heatFF
FF
B(C6F5)2(Me3C6H2)2PH2
![Page 14: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/14.jpg)
Welch, G. C.; San Juan, R. R.; Masuda, J. D.; Stephan, D. W. Science, 2006, 314, 1124-1126.
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C-
and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"
FF
FF
B(C6F5)2(Me3C6H2)2PH
H
heatFF
FF
B(C6F5)2(Me3C6H2)2PH2
![Page 15: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/15.jpg)
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C- and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"2007 - FLPs catalytically
perform hydrogenations
Ph
NtBu
B(C6F5)2(tBu)2P
(5 mol %)1 atm H2 Ph
HNtBu
98%
Ph Ph
B(C6F5)3 (20 mol %)
5 bar H299%
Ph Ph
Me(C6F5)Ph2P (20 mol %)
Chase, P.A.; Welch, G. C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
![Page 16: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/16.jpg)
Mömming, C. M.; Otten, E.; Kehr, G.; Frölich, R.; Grimme, S.; Stephan, D. W.; Erker, G. ACIE, 2009, 48, 6643-6646.
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C- and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"2007 - FLPs catalytically
perform hydrogenations
2008 - FLPs reversiblybind CO2
tBu3P + B(C6F5)3
CO2, 25 ºCO
O
(tBu)3P B(C6F5)3
-CO2, 80 ºCvacuum, 5 hrs
![Page 17: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/17.jpg)
Chen, D.; Wang, Y.; Klankermeyer, J. ACIE, 2010, 49, 9475-9578.
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C- and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"2007 - FLPs catalytically
perform hydrogenations
2008 - FLPs reversiblybind CO2
2010 - Asymmetrichydrogenationof imines with FLPs
N
OMe
Me Me
Me
B(C6F5)2
(5 mol %)
tBu3P (5 mol %)25 bar H2
HN
OMe
MeMe
>99%81% ee
Ph
![Page 18: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/18.jpg)
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C- and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"2007 - FLPs catalytically
perform hydrogenations
2008 - FLPs reversiblybind CO2
2010 - Asymmetrichydrogenationof imines with FLPs
■ I. Theories on the Mechanism of H2 Activation
■ II. Applications of FLPs in Hydrogenation Reactionsand Storage of Small Molecules
![Page 19: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/19.jpg)
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C- and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"2007 - FLPs catalytically
perform hydrogenations
2008 - FLPs reversiblybind CO2
2010 - Asymmetrichydrogenationof imines with FLPs
■ I. Theories on the Mechanism of H2 Activation
■ II. Applications of FLPs in Hydrogenation Reactionsand Storage of Small Molecules
![Page 20: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/20.jpg)
Two Competing Models on the Mechanism of H2 Activation
R3P BR3
R
RR H
H
AR
RR
R
DR
R HH
RR
R
D → σ* donation σ → A donation
Electron Transfer Model
Electric Field Model
![Page 21: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/21.jpg)
Initial Hypotheses on the Mechanism of H2 Activation
B(C6F5)3+tBu3P
Mes3P B(C6F5)3+
[tBu3PH][HB(C6F5)3]
[Mes3PH][HB(C6F5)3]
H2
H2
1 atm
1 atm
Welch, C.; Stephan, D. W. JACS, 2007, 129 , 1880-1881.
![Page 22: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/22.jpg)
Initial Hypotheses on the Mechanism of H2 Activation
B(C6F5)3+tBu3P
Mes3P B(C6F5)3+
[tBu3PH][HB(C6F5)3]
[Mes3PH][HB(C6F5)3]
H2
H2
1 atm
1 atm
PR3 + BR3
BR3H
H
R3P
[R3PH][HBR3]
H H
BR3
R3P
LP (P) → σ* (H2)
σ (H2) → p (B)
Welch, C.; Stephan, D. W. JACS, 2007, 129 , 1880-1881.
![Page 23: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/23.jpg)
■ Multiple H-bonds between C–H---F groups give rise to a preorganized complex
■ Non-directional dispersion forces between tBu and C6F5 groups render the complex flexible
First DFT Study on the Mechanism of H2 Activation
Rokob, T. A.; Hamza, A.; Stirling, A.; Soós, T.; Pápai, I. ACIE, 2008, 120 , 2469-2472.
tBu3P ------ B(C6F5)3
![Page 24: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/24.jpg)
■ Located T.S. features a nearly linear P–H–H–B axis
■ H2 bond elongated from 0.74 A to 0.79 A indicative of an early T.S.
■ 10.4 kcal/mol higher than tBu3P---B(C6F5)3 + H2
First DFT Study on the Mechanism of H2 Activation
Rokob, T. A.; Hamza, A.; Stirling, A.; Soós, T.; Pápai, I. ACIE, 2008, 120 , 2469-2472.
tBu3P --- H–H --- B(C6F5)3
![Page 25: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/25.jpg)
■ Discovered significant H2 polarization
■ Electron transfer proceeds via simultaneous tBu3P → σ∗(H2) and σ(H2) → B(C6F5)3 donation
First DFT Study on the Mechanism of H2 Activation
Rokob, T. A.; Hamza, A.; Stirling, A.; Soós, T.; Pápai, I. ACIE, 2008, 120 , 2469-2472.
tBu3P --- H–H --- B(C6F5)3
![Page 26: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/26.jpg)
First DFT Study on the Mechanism of H2 Activation
Rokob, T. A.; Hamza, A.; Stirling, A.; Soós, T.; Pápai, I. ACIE, 2008, 120 , 2469-2472.
The Electron Transfer Model
■ Non-bonding interactions between bulky substituents lead to a higher E frustrated complex
![Page 27: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/27.jpg)
First DFT Study on the Mechanism of H2 Activation
Rokob, T. A.; Hamza, A.; Stirling, A.; Soós, T.; Pápai, I. ACIE, 2008, 120 , 2469-2472.
The Electron Transfer Model
■ Frustration energy, ΔEt, decreases the activation energy and renders hydrogen splittingfacile and highly exothermic via reactant state destabilization
■ Non-bonding interactions between bulky substituents lead to a higher E frustrated complex
![Page 28: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/28.jpg)
First DFT Study on the Mechanism of H2 Activation
Rokob, T. A.; Hamza, A.; Stirling, A.; Soós, T.; Pápai, I. ACIE, 2008, 120 , 2469-2472.
The Electron Transfer Model
■ Frustration energy, ΔEt, decreases the activation energy and renders hydrogen splittingfacile and highly exothermic via reactant state destabilization
■ Non-bonding interactions between bulky substituents stabilizes both the T.S. and product
■ Non-bonding interactions between bulky substituents lead to a higher E frustrated complex
![Page 29: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/29.jpg)
BP
Mes
Mes
C6F5
C6F5
H HB
P
Mes
Mes
C6F5
C6F5
H2
Linear T.S. not possible for certain tethered FLPs
BP
Mes
Ph
Ph
Mes
BP
Mes
Mes
PhPh
HH
H2
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
![Page 30: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/30.jpg)
(C6F5)3B ---- PtBu3 + H2 (C6F5)2B PMes2+ H2
Calculated T.S. do not have a linear relationship along P–H–H–B axis
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
Calculated T.S. employing a dispersion corrected DFT model:
![Page 31: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/31.jpg)
2-D potential E surface for tBu3P + B(C6F5)3 system
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
2 kcal/mol betweeneach line
incr. E
![Page 32: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/32.jpg)
2 kcal/mol betweeneach line
incr. E
peak
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
![Page 33: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/33.jpg)
peak
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
artificial T.S.
Pápai's non-dispersion corrected DFT model overestimated the P–B bond distance
resulting in a T.S. that is otherwise not present
![Page 34: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/34.jpg)
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
The Electric Field Model
R3P BR3
■ Neglect the FLP as a molecular speciesand replace it by an electric field
■ Polarization from electric field generated inthe interior of the FLP cavity allows for H2 splitting
![Page 35: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/35.jpg)
F = Electric field strength (a.u.)(1 a.u. = 5.1422 x 1011 Vm-1)
Critical field strength needed for H2 splitting is 0.05 – 0.06 a.u.
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
The Electric Field Model
R3P BR3
■ Neglect the FLP as a molecular speciesand replace it by an electric field
■ Polarization from electric field generated inthe interior of the FLP cavity allows for H2 splitting
![Page 36: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/36.jpg)
F = Electric field strength (a.u.)(1 a.u. = 5.1422 x 1011 Vm-1)
Critical field strength needed for H2 splitting is 0.05 – 0.06 a.u.
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
The Electric Field Model
P B
C6F5tBu
C6F5tBuC6F5tBu
0.04 - 0.06 a.u.
B
P
Mes
Mes
C6F5
C6F5
0.04 - 0.06 a.u.
![Page 37: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/37.jpg)
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
The Electric Field Model
■ H-bonding interactions form the FLP while non-directional dispersion forces instillflexibility allowing H2 entry – termed the "preparation step"
![Page 38: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/38.jpg)
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
The Electric Field Model
■ H-bonding interactions form the FLP while non-directional dispersion forces instillflexibility allowing H2 entry – termed the "preparation step"
■ Activation energy is the "preparation step"; after entrance H2 splitting is barrierless
![Page 39: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/39.jpg)
An Alternative Mechanism of H2 Activation
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
The Electric Field Model
■ H-bonding interactions form the FLP while non-directional dispersion forces instillflexibility allowing H2 entry – termed the "preparation step"
■ Activation energy is the "preparation step"; after entrance H2 splitting is barrierless
■ No molecular orbitals arguments invoked; believe this accounts for the similar reactivity of chemically different FLPs
![Page 40: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/40.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
P
tBu
tButBu
B
C6F5
C6F5C6F5
+ B
C6F5
C6F5C6F5
+ B
C6F4H
Mes C6F4H+
NC
NtBu
tBuN
![Page 41: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/41.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
P
tBu
tButBu
B
C6F5
C6F5C6F5
+ B
C6F5
C6F5C6F5
+ B
C6F4H
Mes C6F4H+
NC
NtBu
tBuN
![Page 42: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/42.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
■ At the "critical field" of 0.06 a.u., the activation energy is 75 kcal/mol
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
F = Electric field strength (a.u.)(1 a.u. = 5.1422 x 1011 Vm-1)
![Page 43: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/43.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
■ At the "critical field" of 0.06 a.u., the activation energy is 75 kcal/mol
■ Only at higher electric fields, 0.09 a.u. and above, does the activation energy lowerto a reasonable range (20 kcal/mol or lower)
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
F = Electric field strength (a.u.)(1 a.u. = 5.1422 x 1011 Vm-1)
![Page 44: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/44.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
■ At the "critical field" of 0.06 a.u., the activation energy is 75 kcal/mol
■ Only at higher electric fields, 0.09 a.u. and above, does the activation energy lowerto a reasonable range (20 kcal/mol or lower)
Grimme, S.; Kruse, H.; Goerigk, L.; Erker, G. ACIE, 2010, 49, 1402-1405.
F = Electric field strength (a.u.)(1 a.u. = 5.1422 x 1011 Vm-1)
■ Only at field strengths above 0.1 a.u., does H2 splitting become "barrierless"
![Page 45: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/45.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
P
tBu
tButBu
B
C6F5
C6F5C6F5
+ B
C6F5
C6F5C6F5
+ B
C6F4H
Mes C6F4H+
NC
NtBu
tBuN
![Page 46: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/46.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
P
tBu
tButBu
B
C6F5
C6F5C6F5
+ B
C6F5
C6F5C6F5
+ B
C6F4H
Mes C6F4H+
NC
NtBu
tBuN
![Page 47: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/47.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
P
tBu
tButBu
B
C6F5
C6F5C6F5
+ B
C6F5
C6F5C6F5
+ B
C6F4H
Mes C6F4H+
NC
NtBu
tBuN
EFs within FLP cavities are not homogeneous and are not always strong enough to effect H2 splitting
![Page 48: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/48.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
P
tBu
tButBu
NC
NtBu tBu
N P BMes
MesC6F5
C6F5 B C6F5
C6F5N
MeMe
MeMe P B
Ph
Ph
tBu
tBu
1 2 3 4 5 6+ B(C6F5)3+ B(C6F5)3+ B(C6F5)3
![Page 49: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/49.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
P
tBu
tButBu
NC
NtBu tBu
N P BMes
MesC6F5
C6F5 B C6F5
C6F5N
MeMe
MeMe P B
Ph
Ph
tBu
tBu
1 2 3 4 5 6+ B(C6F5)3+ B(C6F5)3+ B(C6F5)3
For none of the FLPs studied is the EF along the H2 axis high enough to permit H2 splitting
0.09 a.u.
![Page 50: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/50.jpg)
The Electron Transfer Model Revisited
Rokob, T. A.; Bakó, I.; Stirling, A.; Hamza, A.; Pápai, I. JACS, 2013, 135 , 4425-4437.
HH
R
RR H
H
AR
RR
R
DR
R HH
RR
R
HH
■ Use of dispersion corrected DFT basis set results in a generally bent D–H–H–A geometry
■ Deviation from ideal 180º D---H2 angle and 90º H2---A angle due to polarization of the
explained by frontier orbitals aligning themselves for optimal orbital overlap
σ / σ* orbitals of H2
D → σ* donation
σ → A donation
![Page 51: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/51.jpg)
1942 - Brown makes an interesting observation
The Advent of FLP Chemistry
1959 - Wittig finds PPh3 and BPh3 does not form an adduct
1966 - Tochtermann reports Ph3C- and BPh3 trap across olefins;
2006 - Stephan finds FLPscan reversibly split H2
coining of the term "FLP"2007 - FLPs catalytically
perform hydrogenations
2008 - FLPs reversiblybind CO2
2010 - Asymmetrichydrogenationof imines with FLPs
■ I. Theories on the Mechanism of H2 Activation
■ II. Applications of FLPs in Hydrogenation Reactionsand Storage of Small Molecules
![Page 52: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/52.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
F F
F F
(C6F5)2B PR22 R = tBu1 R = Mes N
Ph
tBuHN
Ph
tBu5 mol % cat.
1 atm H2
79% (1)98% (2)
80 ºC
![Page 53: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/53.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
F F
F F
(C6F5)2B PR22 R = tBu1 R = Mes N
Ph
tBuHN
Ph
tBu5 mol % cat.
1 atm H2
79% (1)98% (2)
80 ºC
N
Ph
SO2PhN
Ph
Ph
Ph NPh
PhPh
97% (1)87% (2)
88% (1) 98% (1)
![Page 54: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/54.jpg)
■ Catalytic hydrogenation only possible for sterically hindered imines
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
N
Ph
Ph HN
Ph
Ph
FF
FF
B(C6F5)2Mes2P
5 mol %
5 atm H2120 ºC 5%
![Page 55: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/55.jpg)
■ Catalytic hydrogenation only possible for sterically hindered imines
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
N
Ph
Ph HN
Ph
Ph
FF
FF
B(C6F5)2Mes2P
5 mol %
5 atm H2120 ºC 5%
FF
FF
B(C6F5)2Mes2PN Bn
Bn H
adduct formation between Lewis Basic productand FLP shuts down catalytic activity
![Page 56: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/56.jpg)
■ Catalytic hydrogenation only possible for sterically hindered imines
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
N
Ph
Ph HN
Ph
Ph
FF
FF
B(C6F5)2Mes2P
5 mol %
5 atm H2120 ºC 5%
N
Ph
Ph N
Ph
Ph
FF
FF
B(C6F5)2Mes2P
5 mol %
5 atm H2120 ºC 57%
■ Protecting Imine with B(C6F5)3 recovers catalytic activity
(C6F5)3B (C6F5)3B
![Page 57: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/57.jpg)
■ Catalytic hydrogenation only possible for B(C6F5)3 protected nitriles
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
N HN
R
B(C6F5)3
FF
FF
B(C6F5)2Mes2P
5 mol %
5 atm H2120 ºC
R = Me, 75%
B(C6F5)3
R
Only the amine is isolated (cannot isolate imine)
R = Ph, 84%
![Page 58: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/58.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
![Page 59: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/59.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
HN
Ph
RH
proton transfer
N
Ph
R
![Page 60: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/60.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
HN
Ph
RH
proton transfer
N
Ph
R
HN
Ph
R
![Page 61: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/61.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
HN
Ph
RH
proton transfer
N
Ph
R
HN
Ph
R
Proton transfer precedes hydride deliveryIncreased rates with electron rich imines (R = tBu, 1 hr vs. R = SO2Ph, >10 hrs)
![Page 62: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/62.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
![Page 63: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/63.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
N
Ph
R(C6F5)3B
hydride delivery
N
Ph
R(C6F5)3B
H H
![Page 64: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/64.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
N
Ph
R(C6F5)3B
hydride delivery
N
Ph
R
N
Ph
R(C6F5)3B
(C6F5)3B
H H
H
![Page 65: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/65.jpg)
The First Example of Catalytic Hydrogenations with FLPs
Chase, P. A.; Welch, C.; Jurca, T.; Stephan, D. W. ACIE, 2007, 46, 8050-8053.
Hydrogenation of Imines, Nitriles, and Aziridines
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2P
FF
FF
B(C6F5)2Mes2PH
H
H2
N
Ph
R(C6F5)3B
hydride delivery
N
Ph
R
N
Ph
R
Hydride delivery precedes proton transfer
(C6F5)3B
(C6F5)3B
H H
H
![Page 66: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/66.jpg)
An Improved FLP
Spies, P.; Schwendemann, S.; Lange, S.; Kehr, G.; Fröhlich, R.; Erker, G. ACIE, 2008, 47, 7543-7546.
Hydrogenation of Ketimines and Enamines
Mes2P B(C6F5)2
H2Mes2P
B(C6F5)3
H
H
NtBu
Ph
Mes2P B(C6F5)2
2.5 bar H2r.t.
HNtBu
Ph
87%
20 mol %
![Page 67: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/67.jpg)
An Improved FLP
Spies, P.; Schwendemann, S.; Lange, S.; Kehr, G.; Fröhlich, R.; Erker, G. ACIE, 2008, 47, 7543-7546.
Hydrogenation of Ketimines and Enamines
Mes2P B(C6F5)2
H2Mes2P
B(C6F5)3
H
H
NtBu
Ph
N
MePh
tBu
Mes2P B(C6F5)2
2.5 bar H2r.t.
HNtBu
Ph87%
20 mol %
(5 mol %)70%
NN N
O
(10 mol %)70%
(5 mol %)70%
(3 mol %)70%
![Page 68: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/68.jpg)
Catalytic Hydrogenations Using only B(C6F5)3
Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Comm., 2008, 1701-1703.
Hydrogenation of Imines
NtBu
Ph4 atm H2
B(C6F5)3 (cat.)
toluene, 25 ºC
N
Ph
tBu(C6F5)3B
4 atm H2toluene, 80 ºC
H2NtBu
PhHB(C6F5)3
![Page 69: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/69.jpg)
Catalytic Hydrogenations Using only B(C6F5)3
Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Comm., 2008, 1701-1703.
Hydrogenation of Imines
NtBu
Ph4 atm H2
B(C6F5)3 (cat.)
toluene, 25 ºC
N
Ph
tBu(C6F5)3B
4 atm H2toluene, 80 ºC
H2NtBu
PhHB(C6F5)3
Isolation of zwitterion suggests adduct formation with the product is reversibleand that the B(C6F5)3 catalyst can be recycled
![Page 70: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/70.jpg)
Catalytic Hydrogenations Using only B(C6F5)3
Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Comm., 2008, 1701-1703.
Hydrogenation of Imines
NtBu
Ph4 atm H2
B(C6F5)3 (cat.)
toluene, 25 ºC
N
Ph
tBu(C6F5)3B
4 atm H2toluene, 80 ºC
H2NtBu
PhHB(C6F5)3
Isolation of zwitterion suggests adduct formation with the product is reversible
NtBu
Ph 5 atm H2120 ºC
HNtBu
Ph
89%
5 mol % B(C6F5)3
and that the B(C6F5)3 catalyst can be recycled
![Page 71: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/71.jpg)
Catalytic Hydrogenations Using only B(C6F5)3
Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Comm., 2008, 1701-1703.
Hydrogenation of Imines
NtBu
Ph4 atm H2
B(C6F5)3 (cat.)
toluene, 25 ºC
N
Ph
tBu(C6F5)3B
4 atm H2toluene, 80 ºC
H2NtBu
PhHB(C6F5)3
Isolation of zwitterion suggests adduct formation with the product is reversibleand that the B(C6F5)3 catalyst can be recycled
H2 +N
R
R'
NR
R'
HHB(C6F5)3
B(C6F5)3
![Page 72: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/72.jpg)
Catalytic Hydrogenations Using only B(C6F5)3
Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Comm., 2008, 1701-1703.
Hydrogenation of Imines
NtBu
Ph4 atm H2
B(C6F5)3 (cat.)
toluene, 25 ºC
N
Ph
tBu(C6F5)3B
4 atm H2toluene, 80 ºC
H2NtBu
PhHB(C6F5)3
Isolation of zwitterion suggests adduct formation with the product is reversibleand that the B(C6F5)3 catalyst can be recycled
H2 +N
R
R'
NR
R'
HHB(C6F5)3
N
R'
B(C6F5)3
H
HR
B(C6F5)3
![Page 73: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/73.jpg)
Catalytic Hydrogenations Using only B(C6F5)3
Chase, P. A.; Jurca, T.; Stephan, D. W. Chem. Comm., 2008, 1701-1703.
Hydrogenation of Imines
NtBu
Ph4 atm H2
B(C6F5)3 (cat.)
toluene, 25 ºC
N
Ph
tBu(C6F5)3B
4 atm H2toluene, 80 ºC
H2NtBu
PhHB(C6F5)3
Isolation of zwitterion suggests adduct formation with the product is reversibleand that the B(C6F5)3 catalyst can be recycled
H2 +N
R
R'
NR
R'
HHB(C6F5)3
N
R'
B(C6F5)3
H
HR
NHR
R'
B(C6F5)3
![Page 74: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/74.jpg)
Expanding the Scope to Oxygenated Substrates
Wang, H.; Fröhlich, R.; Kehr, G.; Erker, G. Chem. Comm., 2008, 5966-5968.
Hydrogenation of Silyl Enol Ethers
PPh2 PPh2 PPh2 PPh2H
HB(C6F5)3
H2, r.t.
–H2, 60 ºC
![Page 75: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/75.jpg)
Expanding the Scope to Oxygenated Substrates
Wang, H.; Fröhlich, R.; Kehr, G.; Erker, G. Chem. Comm., 2008, 5966-5968.
Hydrogenation of Silyl Enol Ethers
PPh2 PPh2 PPh2 PPh2H
HB(C6F5)3
H2, r.t.
–H2, 60 ºC
R
OTMS
R
OTMS
R'
20 mol % cat.
2 bar H2, r.t.
![Page 76: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/76.jpg)
Expanding the Scope to Oxygenated Substrates
Wang, H.; Fröhlich, R.; Kehr, G.; Erker, G. Chem. Comm., 2008, 5966-5968.
Hydrogenation of Silyl Enol Ethers
PPh2 PPh2 PPh2 PPh2H
HB(C6F5)3
H2, r.t.
–H2, 60 ºC
OTMS
Ph
OTMS
tBu
OTMS OTMS
Me
OTMS
R
OTMS
R
OTMS20 mol % cat.
2 bar H2, r.t.
93% 89% 86% 85% >99%
B(C6F5)3
R'R
![Page 77: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/77.jpg)
Studies of Hantzsch Ester with B(C6F5)3 Unveils New Substrates
Geier, S. J.; Chase, P. A.; Stephan, D. W. Chem. Comm., 2010, 46, 4884-4886.
Hydrogenation of N-heterocycles
NH
Me Me
O
OEt
O
EtO
NH
Me Me
O
OEt
O
EtO B(C6F5)3 HB(C6F5)3
-40 ºC NH
Me Me
O
OEt
O
EtO
-20 ºCH
B(C6F5)3
60% 55%(70% at r.t.)
Webb, J. D.; Laberge, V. S.; Geier, S. J.; Stephan, D. W.; Crudden, C. M. Chem. Eur. J., 2010, 16 , 4895-4902.
![Page 78: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/78.jpg)
Studies of Hantzsch Ester with B(C6F5)3 Unveils New Substrates
Geier, S. J.; Chase, P. A.; Stephan, D. W. Chem. Comm., 2010, 46, 4884-4886.
Hydrogenation of N-heterocycles
NH
Me Me
O
OEt
O
EtO
NH
Me Me
O
OEt
O
EtO B(C6F5)3 HB(C6F5)3
-40 ºC NH
Me Me
O
OEt
O
EtO
-20 ºCH
B(C6F5)3
60% 55%(70% at r.t.)
Webb, J. D.; Laberge, V. S.; Geier, S. J.; Stephan, D. W.; Crudden, C. M. Chem. Eur. J., 2010, 16 , 4895-4902.
Observation of hydride delivery into pyridinium inspiredexperimentation with N-heterocycle substrates
![Page 79: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/79.jpg)
Studies of Hantzsch Ester with B(C6F5)3 Unveils New Substrates
Geier, S. J.; Chase, P. A.; Stephan, D. W. Chem. Comm., 2010, 46, 4884-4886.
Hydrogenation of N-heterocycles
NH
Me Me
O
OEt
O
EtO
NH
Me Me
O
OEt
O
EtO B(C6F5)3 HB(C6F5)3
-40 ºC NH
Me Me
O
OEt
O
EtO
-20 ºCH
B(C6F5)3
60% 55%(70% at r.t.)
Webb, J. D.; Laberge, V. S.; Geier, S. J.; Stephan, D. W.; Crudden, C. M. Chem. Eur. J., 2010, 16 , 4895-4902.
Observation of hydride delivery into pyridinium inspiredexperimentation with N-heterocycle substrates
N
5 mol % B(C6F5)3
4 atm H2, 2 hrs, r.t. NH80%
NH
HB(C6F5)3
![Page 80: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/80.jpg)
Studies of Hantzsch Ester with B(C6F5)3 Unveils New Substrates
Geier, S. J.; Chase, P. A.; Stephan, D. W. Chem. Comm., 2010, 46, 4884-4886.
Hydrogenation of N-heterocycles
NH
Me Me
O
OEt
O
EtO
NH
Me Me
O
OEt
O
EtO B(C6F5)3 HB(C6F5)3
-40 ºC NH
Me Me
O
OEt
O
EtO
-20 ºCH
B(C6F5)3
60% 55%
Webb, J. D.; Laberge, V. S.; Geier, S. J.; Stephan, D. W.; Crudden, C. M. Chem. Eur. J., 2010, 16 , 4895-4902.
Observation of hydride delivery into pyridinium inspiredexperimentation with N-heterocycle substrates
N
5 mol % B(C6F5)3
2 hrs, r.t. NH80%
NH
Ph NH
Me NH
MeN
NH
80% 74% 88% 84%
![Page 81: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/81.jpg)
Aromatic Hydrogenation
Mahdi, T.; Heiden, Z. M.; Grimme, S.; Stephan, D. W. JACS, 2012, 134 , 4088-4091.
Hydrogenation of Anilines to Cyclohexylamines
NHtBu
Ph
B(C6F5)3
H2, 25 ºCNH2
tBu
PhHB(C6F5)3
110 ºC
H2NH2
tBu
HB(C6F5)3
93%
![Page 82: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/82.jpg)
Aromatic Hydrogenation
Mahdi, T.; Heiden, Z. M.; Grimme, S.; Stephan, D. W. JACS, 2012, 134 , 4088-4091.
Hydrogenation of Anilines to Cyclohexylamines
NHtBu
Ph
B(C6F5)3
H2, 25 ºCNH2
tBu
PhHB(C6F5)3
110 ºC
H2NH2
tBu
HB(C6F5)3
93%
NH2
HB(C6F5)3
NH2iPr
HB(C6F5)3
Me
NH2iPr
HB(C6F5)3
OMe
NH2iPr
Me MeHB(C6F5)3
65%, 96 hrs 77%, 36 hrs 61%, 36 hrs 48%, 72 hrs
![Page 83: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/83.jpg)
Aromatic Hydrogenation
Mahdi, T.; Heiden, Z. M.; Grimme, S.; Stephan, D. W. JACS, 2012, 134 , 4088-4091.
Hydrogenation of Anilines to Cyclohexylamines
NHtBu
Ph
B(C6F5)3
H2, 25 ºCNH2
tBu
PhHB(C6F5)3
110 ºC
H2NH2
tBu
HB(C6F5)3
93%
NH2
HB(C6F5)3
NH2iPr
HB(C6F5)3
Me
NH2iPr
HB(C6F5)3
OMe
NH2iPr
Me MeHB(C6F5)3
65%, 96 hrs 77%, 36 hrs 61%, 36 hrs 48%, 72 hrs
NPh
PhPhPh
Ph
H2N HB(C6F5)3
50%, 96 hrs
5 mol % B(C6F5)3
H2, 110 ºC
![Page 84: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/84.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
(C6F5)Ph2P B(C6F5)3 [(C6F5)Ph2PH] [HB(C6F5)3]+H2
cation posseses much greater bronsted acidity
![Page 85: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/85.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
(C6F5)Ph2P B(C6F5)3 [(C6F5)Ph2PH] [HB(C6F5)3]+H2
cation posseses much greater bronsted acidity
Ph
Ph
20 mol % (C6F5)Ph2P20 mol % B(C6F5)3 Ph
PhMe
5 bar H2, r.t.
99%
![Page 86: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/86.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
(C6F5)Ph2P B(C6F5)3 [(C6F5)Ph2PH] [HB(C6F5)3]+H2
cation posseses much greater bronsted acidity
Ph
Ph
20 mol % (C6F5)Ph2P20 mol % B(C6F5)3 Ph
PhMe
5 bar H2, r.t.
99%
Ph
Ph
Ph
PhMe
NPh
Ph
Me
H HB(C6F5)3
HB(C6F5)3
hydride delivery
Friedel Crafts
Ph2NMeNMePh
PhMe
Ph
Ph
PhMe
69%
31%
![Page 87: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/87.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
R
R
R
RMe HB(C6F5)3
[(C6F5)Ph2PH] [HB(C6F5)3]
proton transfer hydride delivery
R
RMe
![Page 88: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/88.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
R
R
R
RMe HB(C6F5)3
[(C6F5)Ph2PH] [HB(C6F5)3]
proton transfer hydride delivery
R
RMe
Me Me
Me
96% 85%
![Page 89: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/89.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
R
R
R
RMe HB(C6F5)3
[(C6F5)Ph2PH] [HB(C6F5)3]
proton transfer hydride delivery
R
RMe
Me Me Me
Me MeO
96% 85% 30%
![Page 90: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/90.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
R
R
R
RMe HB(C6F5)3
[(C6F5)Ph2PH] [HB(C6F5)3]
proton transfer hydride delivery
R
RMe
Me Me Me
Me MeO
Me
Cl
96% 85% 30% 10%
![Page 91: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/91.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
R
R
R
RMe HB(C6F5)3
[(C6F5)Ph2PH] [HB(C6F5)3]
proton transfer hydride delivery
R
RMe
Me Me Me
Me MeO
Me
Cl
TMSMe
96% 85% 30% 10% 95%
![Page 92: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/92.jpg)
Hydrogenation of Non-Polar Substrates
Greb, L.; Ona-Burgos, P.; Schirmer, B.; Grimme, S.; Stephan, D. W.; Paradies, J. ACIE, 2012, 51, 10164-10168.
Hydrogenation of Olefins
R
R
R
RMe HB(C6F5)3
[(C6F5)Ph2PH] [HB(C6F5)3]
proton transfer hydride delivery
R
RMe
Me Me Me
Me MeO
Me
Cl
TMSMe
Me Me
Me
Me Me
96% 85% 30% 10% 95%
99%
99%
![Page 93: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/93.jpg)
Hydrogenation of Non-Polar Substrates
Chernichenko, K.; Madarász, A.; Pápai, I.; Nieger, M.; Leskela, M.; Repo, T. Nat. Chem., 2013, 5, 718-723.
Hydrogenation of Alkynes to Cis-Alkenes
R'R
NMe2
B
C6F5
H
NMe2
B
C6F5
R'
R
H
![Page 94: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/94.jpg)
Hydrogenation of Non-Polar Substrates
Chernichenko, K.; Madarász, A.; Pápai, I.; Nieger, M.; Leskela, M.; Repo, T. Nat. Chem., 2013, 5, 718-723.
Hydrogenation of Alkynes to Cis-Alkenes
R'R
NMe2
B
C6F5
H
NMe2
B
C6F5
R'
R
H
N
BC6F5
R'
R
H
Me Me
H
H
H2
![Page 95: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/95.jpg)
Hydrogenation of Non-Polar Substrates
Chernichenko, K.; Madarász, A.; Pápai, I.; Nieger, M.; Leskela, M.; Repo, T. Nat. Chem., 2013, 5, 718-723.
Hydrogenation of Alkynes to Cis-Alkenes
R'R
NMe2
B
C6F5
H
NMe2
B
C6F5
R'
R
H
N
BC6F5
R'
R
H
Me Me
H
H
H
R
R'H
H2
![Page 96: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/96.jpg)
Hydrogenation of Non-Polar Substrates
Chernichenko, K.; Madarász, A.; Pápai, I.; Nieger, M.; Leskela, M.; Repo, T. Nat. Chem., 2013, 5, 718-723.
Hydrogenation of Alkynes to Cis-Alkenes
R'R
NMe2
B
C6F5
H
NMe2
B
C6F5
R'
R
H
N
BC6F5
R'
R
H
Me Me
H
H
H
R
R'H
H2
NMe2
B
C6F5
C6F5
N
BC6F5
Me Me
H
H
FF
F
FF
H2
80 ºC
![Page 97: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/97.jpg)
Hydrogenation of Non-Polar Substrates
Chernichenko, K.; Madarász, A.; Pápai, I.; Nieger, M.; Leskela, M.; Repo, T. Nat. Chem., 2013, 5, 718-723.
Hydrogenation of Alkynes to Cis-AlkenesNMe2
B
C6F5
C6F5
N
BC6F5
Me Me
H
H
FF
F
FF
H2
80 ºC D2NMe2
B
C6F5
D
H
R
R'D
+
R'R
NMe2
B
C6F5
H
NMe2
B
C6F5
R'
R
H
N
BC6F5
R'
R
H
Me Me
H
H
H
R
R'H
H2
![Page 98: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/98.jpg)
NOMe
MePh
Chen, D.; Wang, Y.; Klankermeyer, J. ACIE, 2010, 49, 9475-9578.
N
OMe
Me Me
Me
B(C6F5)2
(5 mol %)
tBu3P (5 mol %)25 bar H2
HN
OMe
MeMe
>99%81% ee
Asymmetric Catalytic HydrogenationHydrogenation of Imines
Me Me
Me
BC6F5
H
F FF
FF
Me Me
Me
BH
C6F5
NMe
FF F
FF
favored approach disfavored approach
Ph
![Page 99: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/99.jpg)
tBu3P + B(C6F5)3
CO2, 25 ºCO
O
(tBu)3P B(C6F5)3
80 ºCvacuum, 5 hrs
Applications in Green Chemistry
Mömming, C. M.; Otten, E.; Kehr, G.; Fröhlich, R.; Grimme, S.; Stephan, D. W.; Erker, G. ACIE, 2009, 48, 6643-6646.
Reversible CO2 Binding
Mes2P
B(C6F5)3
Mes2P B(C6F5)3
CO2, 25 ºC
CH2Cl2, > -20 ºC
-CO2
-CO2
OO
Mes2P B(C6F5)3
87%
79%
![Page 100: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/100.jpg)
Applications in Green Chemistry
Sajid, M. et. al. Chem. Sci., 2013, 4, 213-219.
SO2 and N2O Binding
tBu3P + B(C6F5)3
SO2, 25 ºCS O
O
(tBu)3P B(C6F5)3
Mes2P
B(C6F5)3
Mes2P B(C6F5)3
SO2, -75 ºCS O
O
Mes2P B(C6F5)3
80%
83%
*
■ SO2 is a major air pollutant, precursor to acid rain
![Page 101: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/101.jpg)
Applications in Green Chemistry
Sajid, M. et. al. Chem. Sci., 2013, 4, 213-219.
SO2 and N2O Binding
tBu3P + B(C6F5)3
SO2, 25 ºCS O
O
(tBu)3P B(C6F5)3
Mes2P
B(C6F5)3
Mes2P B(C6F5)3
SO2, -75 ºCS O
O
Mes2P B(C6F5)3
80%
83%
*
■ SO2 is a major air pollutant, precursor to acid rain
■ N2O is a minor constituent in the atmosphere, but ~300x more potent as a greenhouse gas
tBu3P + B(C6F5)3
N2O, 25 ºCO
B(C6F5)3
76%
NN
(tBu)3P
Otten, E.; Neu, R. C.; Stephan, D. W. JACS, 2009, 131 , 9918-9919.
![Page 102: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/102.jpg)
Applications in Green Chemistry
Berkefeld, A.; Piers, W. E.; Parvez, M. JACS, 2010, 132 , 10660-10661.
Converting CO2 to Fuels
■ Addition of Et3SiH to CO2 in the presence of an FLP efficiently reduces CO2 to CH4
HB(C6F5)3NH2
MeMe
MeMe
![Page 103: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/103.jpg)
Applications in Green Chemistry
Berkefeld, A.; Piers, W. E.; Parvez, M. JACS, 2010, 132 , 10660-10661.
Converting CO2 to Fuels
■ Addition of Et3SiH to CO2 in the presence of an FLP efficiently reduces CO2 to CH4
HB(C6F5)3NH2
MeMe
MeMe
OO B(C6F5)3
HTMPH
CO2
![Page 104: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/104.jpg)
Applications in Green Chemistry
Berkefeld, A.; Piers, W. E.; Parvez, M. JACS, 2010, 132 , 10660-10661.
Converting CO2 to Fuels
■ Addition of Et3SiH to CO2 in the presence of an FLP efficiently reduces CO2 to CH4
HB(C6F5)3NH2
MeMe
MeMe
Et3SiH + B(C6F5)3
HEt3Si B(C6F5)3
OO B(C6F5)3
HTMPH
CO2
OO SiEt3
H
![Page 105: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/105.jpg)
Applications in Green Chemistry
Berkefeld, A.; Piers, W. E.; Parvez, M. JACS, 2010, 132 , 10660-10661.
Converting CO2 to Fuels
■ Addition of Et3SiH to CO2 in the presence of an FLP efficiently reduces CO2 to CH4
HB(C6F5)3NH2
MeMe
MeMe
Et3SiH + B(C6F5)3
HEt3Si B(C6F5)3
OO B(C6F5)3
HTMPH
CO2
OO SiEt3
H
OO SiEt3
Et3SiH
H
HEt3Si B(C6F5)3 –B(C6F5)3
![Page 106: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/106.jpg)
Applications in Green Chemistry
Berkefeld, A.; Piers, W. E.; Parvez, M. JACS, 2010, 132 , 10660-10661.
Converting CO2 to Fuels
■ Addition of Et3SiH to CO2 in the presence of an FLP efficiently reduces CO2 to CH4
HB(C6F5)3NH2
MeMe
MeMe
Et3SiH + B(C6F5)3
HEt3Si B(C6F5)3
OO B(C6F5)3
HTMPH
CO2
OO SiEt3
H
OO SiEt3
Et3SiH
H
HEt3Si B(C6F5)3
HEt3Si B(C6F5)3 O
H
Et3SiH
H(Et3Si)2O
–B(C6F5)3
+ B(C6F5)3
![Page 107: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/107.jpg)
Applications in Green Chemistry
Berkefeld, A.; Piers, W. E.; Parvez, M. JACS, 2010, 132 , 10660-10661.
Converting CO2 to Fuels
■ Addition of Et3SiH to CO2 in the presence of an FLP efficiently reduces CO2 to CH4
HB(C6F5)3NH2
MeMe
MeMe
Et3SiH + B(C6F5)3
HEt3Si B(C6F5)3
OO B(C6F5)3
HTMPH
CO2
OO SiEt3
H
OO SiEt3
Et3SiH
H
HEt3Si B(C6F5)3
HEt3Si B(C6F5)3 O
H
Et3SiH
H(Et3Si)2O
HEt3Si B(C6F5)3
(Et3Si)2O
HCH3
–B(C6F5)3
+ B(C6F5)3 + B(C6F5)3
![Page 108: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/108.jpg)
Limitations and Future Directions
Sumerin, V.; Schulz, F.; Nieger, M.; Leskelä, M.; Repo, T.; Rieger, B. ACIE, 2008, 47, 6001-6003.
■ Currently cannot hydrogenate aldehydes or ketones catalytically
■ Discovery of better FLP catalysts for asymmetric induction; expanding the scope
■ Hydrogen gas storage - currently FLPs can achieve 0.25 wt % H2; whereas to be practicalneed 6 - 9 wt % H2 (i.e. ammonia-borane)
NH2 Me
MeMeMe
HB(C6F5)3
O
H
20 ºC, 1hr
OB(C6F5)3
NH2 Me
MeMeMe
95%
to olefin hydrogenations
![Page 109: The Chemistry of Frustrated Lewis Pairs Chemistry of Frustrated Lewis Pairs MacMillan Group Meeting 4 December 2013 Tracy Liu B RR R N R R R B RR R N R R R B RR R N R R R BN R R R](https://reader034.vdocuments.net/reader034/viewer/2022050804/5ade73687f8b9aeb668e4f06/html5/thumbnails/109.jpg)
Summary
■ I. Theories on the Mechanism of H2 Activation
■ Electron Transfer Model that Invokes Frontier Molecular Orbitals
■ Electric Field Model that disregards Frontier Molecular Orbitals
■ Secondary non-covalent interactions play key role in lowering H2 activation barrier
■ II. Applications of FLPs in Hydrogenation Reactions and Storage of Small Molecules
■ Catalytic hydrogenation of imines, enamines, nitriles, aziridines, silyl enol ethers,
■ Stoichiometric hydrogenations of aldehydes, ketones
■ Asymmetric imine hydrogenations
cyclic ethers, alkenes, alkynes, ynones
■ Advances in area of green chemistry