deactivation pathways in transition metal catalysis · pdf filecrabtree, r. h. chem. rev....
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Poater, A.; Cavallo, L. Theor. Chem. Acc. 2012, 131 , 1155.
Deactivation Pathways in Transition Metal CatalysisWhy Study Catalyst Decomposition?
active for
catalysis
inactive for
catalysis
decomposition
"One of the reasons for [the] limited understanding [of catalyst deactivation] is that academic groups usually focus on the more rewarding improvement of activity and/or selectivity of a catalyst, since more or less rational strategies
can be followed, rather than investing resources to follow catalyst deactivation along unexplored pathways."
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0 10 20 30 40 50 60 70 80
% C
atal
yst
Number of Cycles
–
Deactivation Pathways in Transition Metal CatalysisWhy Study Catalyst Decomposition?
What happens if you lose 10% of your catalyst each cycle? 5%? 2%?
Deactivation is much more studied in industrial
settings where low catalyst loadings are critical.
Even a modest improvement can have a large effect on TON!
Crabtree, R. H. Chem. Rev. 2015, 115 , 127.
Deactivation Pathways in Transition Metal CatalysisWhy Study Catalyst Decomposition?
decomposition
But first, some definitions:
Irreversible processes that involves extensive breakup of bonds in a chemical structure:
n Degredation: deletirious ligand functionalization or bond rupture
n Decomposition: collapse of the metal complex as a whole
n Deactivation: permanent loss in catalytic activity
n Inhibition: reversible process that leads to loss in activity
Crabtree, R. H. Chem. Rev. 2015, 115 , 127.
Deactivation Pathways in Transition Metal CatalysisA Scarce Topic in the Literature
Ligand loss or deleterious functionalization
Multimetallic processes, cluster formation
Catalyst poisons
Substrate or product inhibition
LnPd(0)
MN
N
N
NM
CN– CO thiols O2
N
BrN
O
Deactivation Pathways in Transition Metal CatalysisOutline
N N
RuCl
H2Ir
L
IrH2
PCy3PCy3
L
L
Cy3P
HH2Ir
2+
IrIII
N
NN
2+
N
Hydrogenation Cross Metathesis Photoredox
Xu, Y.; Mingos, M. P.; Brown, J. M. Chem. Commun. 2008, 199.
Deactivation Pathways in Transition Metal CatalysisCrabtree's Catalyst
IrN
PCy3
+ Crabtree's Catalyst
n discovered in 1977n reactivity for tetrasubstituted olefins
MeMe
Me Me
Me
Me
catalyst
RhCl(PPh3)3
[Rh(cod)(PPh3)2]PF6
[Ir(cod)PCy3(py)]PF6
TOF (mol substrate per mol cat. per hour)
60 70 0 0
4000 10 0 0
6400 4500 3800 4000
Brown, J. M. Angew. Chem. Int. Ed. Engl. 1987, 26, 190.
Deactivation Pathways in Transition Metal CatalysisCrabtree's Catalyst
IrN
PCy3
+
C
A B
D H2, CH2Cl2
A B
C DH H
Me
OHMe
Me
OHMe
20 mol% cat, 99:1 dr
Me CO2Me Me CO2Me
2 mol% cat, 89:11 dr
Verendel, J. J.; Pàmies, O.; Diéguez, M.; Andersson, P. G. Chem. Rev. 2014, 114 , 2130.
Deactivation Pathways in Transition Metal CatalysisCrabtree's Catalyst
Ir
H
S
py
H
PCy3
S
Ir
H
S
py
H
PCy3
Ir
H
S
py
H
PCy3 migratoryinsertion
Ir
S
py
H
PCy3
H
reductiveelimination
SH2
H3CCH3
Ir
S
H
py
H
PCy3
Ir
H
py
H
PCy3
Ir
H
py
H
PCy3 migratoryinsertion
reductiveelimination
S
H3CCH3
Ir
H
H
py
H
PCy3
H
H H
HH
H2
IrI/IrIII IrIII /IrV
Verendel, J. J.; Pàmies, O.; Diéguez, M.; Andersson, P. G. Chem. Rev. 2014, 114 , 2130.
Deactivation Pathways in Transition Metal CatalysisCrabtree's Catalyst
Ir
H
S
py
H
PCy3
S
Ir
H
S
py
H
PCy3
Ir
H
S
py
H
PCy3 migratoryinsertion
Ir
S
py
H
PCy3
H
reductiveelimination
SH2
H3CCH3
Ir
S
H
py
H
PCy3
Ir
H
py
H
PCy3
Ir
H
py
H
PCy3 migratoryinsertion
reductiveelimination
S
H3CCH3
Ir
H
H
py
H
PCy3
H
H H
HH
H2
IrI/IrIII IrIII /IrV
Ir
Xu, Y.; Mingos, M. P.; Brown, J. M. Chem. Commun. 2008, 199.
Deactivation Pathways in Transition Metal CatalysisCrabtree's Catalyst
H2Ir
L
IrH2
PCy3PCy3
L
L
Cy3P
HH2Ir
2+
H2, CH2Cl2
low [alkene]–
K2PtCl4
N
PCy3
+
n bulkier ligands can prevent trimerisation through steric hindrance
n low catalyst concentration can prevent trimerisation
n complexes with BArF counterion rather than PF6 are less moisture sensitive
Lightfoot, A.; Schnider, P.; Pfaltz, A. Angew. Chem. Int. Ed. 1998, 37, 2897.
Deactivation Pathways in Transition Metal CatalysisCrabtree's Catalyst
H2, CH2Cl2
n complexes with BArF counterion rather than PF6 are less moisture sensitive
P NIr
O
tBu
o-tolo-tol
+ X–
Me
MeO
Me
MeO
X– mol% cat. conditions conversion %
PF6–
PF6–
BArF–
4%
4%
0.3%
–
rigorously dry
–
57%
99%
99%
Deactivation Pathways in Transition Metal CatalysisOutline
N N
RuCl
H2Ir
L
IrH2
PCy3PCy3
L
L
Cy3P
HH2Ir
2+
IrIII
N
NN
2+
N
Hydrogenation Cross Metathesis Photoredox
Deactivation Pathways in Transition Metal CatalysisOlefin Metathesis Catalysts
EtO2C CO2EtCO2EtEtO2C metathesis cat.
–
Schrock Chauvin Grubbs
PCy3
RuCl
PCy3
Cl
Ph 10 minutesPCy3 [Ru]
H2N NH2
unidentified, inactivebyproducts
Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Metathesis Catalysts
unstable to:
n coordinating solvents (MeCN, DMSO, etc.)
n lewis basic functionality
n amines in particular
PCy3
RuCl
PCy3
Cl
Ph
Grubbs generation I
PCy3
RuCl
PCy3
Cl
Ph 10 minutesPCy3 [Ru]
H2N NH2
unidentified, inactivebyproducts
Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
Deactivation Pathways in Transition Metal CatalysisOlefin Metathesis Catalysts
RuR
RuR
RR Ru products
Bimolecular Catalyst Decomposition
Crabtree, R. H. J. Organomet. Chem. 2005, 690, 5451.
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Metathesis Catalysts
P
P
Me
MeMe
iPr
iPr
iPrMeO
OMe
PCy2N
Me
MeMe
NMe
MeMe
widely studied 2 e– spectator ligand
sterically and electronically tunable
strong σ-donor, weak π-acceptor
very tight binding to metal
sterically large ligand
Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18.
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Metathesis Catalysts
RuCl
PCy3
Cl
Ph
NN MesMes
Functional Group Tolerance
R
O
OHRHO O
HHR
O
HR
O
R R
O
NH
RR
O
OR
Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Methathesis Catalysts
RuCl
PCy3
Cl
Ph
NN MesMes
RuCl
NH
Cl
Ph
NN MesMes
HNMe
Me
4 5
CO2EtEtO2C
RCM
ROMP
–
NH2Me
Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Metathesis Catalysts
RuCl
PCy3
Cl
Ph
NN MesMes
RuCl
NH
Cl
Ph
NN MesMes
HNMe
Me
4 5
CO2EtEtO2C
RCM
ROMP
–
NH2Me
bulky small
Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Metathesis Catalysts
NN MesMes
RuCl
OCl
iPr
1 mol%
amine (n mol%)PhH, 60 ºC, 24 h
Ph PhPh
Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
Deactivation Pathways in Transition Metal CatalysisOlefin Metathesis Catalysts
RuCl
L
Cl
Ph
NN MesMes
L
H2NR
RuCl
L
Cl
Ph
NN MesMes
LH2N R Ru
ClL
Cl
NN MesMes
L RuCl
L
L
Cl
NN MesMes
L
Benzylidene abstraction
+ L
Ph NH
R
Lummiss, J. A. M.' McClennan, W. L.; McDonald, R.; Fogg, D. E. Organometallics 2014, 33, 6738.
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Metathesis Catalysts
Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
Deactivation Pathways in Transition Metal CatalysisOlefin Metathesis Catalysts
RuCl
L
Cl
Ph
NN MesMes
L
H2NR
RuCl
L
Cl
Ph
NN MesMes
LH2N R Ru
ClL
Cl
NN MesMes
L RuCl
L
L
Cl
NN MesMes
L
Benzylidene abstraction
+ L
Ph NH
R
Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
Deactivation Pathways in Transition Metal CatalysisOlefin Metathesis Catalysts
RuCl
L
Cl
Ph
NN MesMes
L
H2NR
RuCl
L
Cl
Ph
NN MesMes
LH2N R Ru
ClL
Cl
NN MesMes
L RuCl
L
L
Cl
NN MesMes
L
Benzylidene abstraction
+ L
Ph NH
R
Metallacyclobutane deprotonation
RuCl
Cl
R
H2IMes RuH2IMes
Cl
Cl Ph
RH
H
Ph
NR3RuH2IMes
Cl
Cl
R
PhHNR3+
R
Ph
Ru decomp.
Hong, S. H.; Chlenov, A.; Day, M. W.; Grubbs, R. H. Angew. Chem. Int. Ed. 2007, 46, 5148.
Deactivation Pathways in Transition Metal CatalysisOlefin Methathesis Catalysts
RuCl
PCy3
Cl
Ph
NN MesMes N N
RuCl
OCl
Me
Me
N N
RuCl
Cl
Ph
PCy3
EEMe MeEE
Me Me
metathesis catalyst
CH2Cl2, 24 h
yield = 0% yield = 76% yield = >95%
Hong, S. H.; Chlenov, A.; Day, M. W.; Grubbs, R. H. Angew. Chem. Int. Ed. 2007, 46, 5148.
Deactivation Pathways in Transition Metal CatalysisOlefin Metathesis Catalysts
RuCl
PCy3
Cl
Ph
NN MesMes N N
RuCl
OCl
Me
Me
N N
RuCl
Cl
Ph
PCy3
EEMe MeEE
Me Me
metathesis catalyst
CH2Cl2, 24 h
yield = 0% yield = 76% yield = >95%
Hong, S. H.; Chlenov, A.; Day, M. W.; Grubbs, R. H. Angew. Chem. Int. Ed. 2007, 46, 5148.
Deactivation Pathways in Transition Metal CatalysisOlefin Methathesis Catalysts
N N
RuCl
Cl
Ph
PCy3
40 ºC
CH2Cl2, 12 h
N
RuCl
N N
RuCl
N
24% 38%
Hong, S. H.; Chlenov, A.; Day, M. W.; Grubbs, R. H. Angew. Chem. Int. Ed. 2007, 46, 5148.
Deactivation Pathways in Transition Metal CatalysisOlefin Methathesis Catalysts
N N PhPh
RuCl
Cl
Ph
PCy3
N
Ru
NN
Ru
N
– PCy3N N PhPh
RuCl
Cl
Ph Cl
Cl H
Ph
NN
RuCl
Cl
Ph
Cl
Cl
C–H activation hydride insertion
R.E. 40 ºC
CH2Cl2, > 7 daysno reaction
Hong, S. H.; Chlenov, A.; Day, M. W.; Grubbs, R. H. Angew. Chem. Int. Ed. 2007, 46, 5148.
Deactivation Pathways in Transition Metal CatalysisOlefin Metathesis Catalysts
N
Ru
N
Cl
Cl
1.2 equiv PCy3
CH2Cl2, 36 h
N N
RuCl
quantitative
HPCy3+Cl–
PCy3 assistance required for second C–H insertion
Hong, S. H.; Chlenov, A.; Day, M. W.; Grubbs, R. H. Angew. Chem. Int. Ed. 2007, 46, 5148.
Deactivation Pathways in Transition Metal CatalysisOlefin Methathesis Catalysts
RuCl
PCy3
Cl
Ph
NN MesMes N N
RuCl
OCl
Me
Me
N N
RuCl
Cl
Ph
PCy3
EEMe MeEE
Me Me
metathesis catalyst
CH2Cl2, 24 h
yield = 0% yield = 76% yield = >95%
–
Deactivation Pathways in Transition Metal Catalysis
–
Olefin Metathesis Catalysts
RuCl
PCy3
Cl
Ph
NN MesMes
A metathesis catalyst that tolerates free amines has yet to be reported.
Deactivation Pathways in Transition Metal CatalysisOutline
N N
RuCl
H2Ir
L
IrH2
PCy3PCy3
L
L
Cy3P
HH2Ir
2+
IrIII
N
NN
2+
N
Hydrogenation Cross Metathesis Photoredox
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
most organicmolecules
photoredoxcatalysts
absorb light fromordinary light bulbs
Targeted delivery of energy via selective excitation of photoredox catalyst
200 nm 300 nm 400 nm 500 nm 600 nm 700 nm
Visible lightUV light
IrIIIN
N
N
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
IrIIIN
N
N
Photons converted into ~55 kcal/mol chemical potential energy
Typical reaction: oxidation or reduction
New paradigm for reaction development
Photoredox reaction: oxidation and reduction
Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
IrIIIN
N
N
Ir(ppy)3 (0.375 mol%)
NaHCO3, DMAblue LED
NH
Me
NH
MeCO2Et
BrO
OEt
3 equiv 85%2
Ir(ppy)3
Kinetic analysis indicates:
(1) substrate or product inhibition, or
(2) [Ir(ppy)3] is not constant due to deactivation
Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
PhotoredoxCatalytic Cycle
SET
SET
IrIV
IrIII
visible light
oxidant
*IrIII
reductant
BrO
OEt
O
OEt
NH
Me
NH
MeCO2Et
NH
MeCO2Et
NH
MeCO2Et– H+
Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
IrIIIN
N
N
Ir(ppy)3 (0.375 mol%)
NaHCO3, DMAblue LED
NH
Me
NH
MeCO2Et
BrO
OEt
3 equiv 85%2
Ir(ppy)3
Kinetic analysis indicates:
(1) substrate or product inhibition, or
(2) [Ir(ppy)3] is not constant due to deactivation
Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
IrIIIN
N
N
Ir(ppy)3 (0.375 mol%)
NaHCO3, DMAblue LED
NH
Me
NH
MeCO2Et
BrO
OEt
3 equiv 85%2
Ir(ppy)3
Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
IrIIIN
N
N
Ir(ppy)3 (0.375 mol%)
NaHCO3, DMAblue LED
NH
Me
NH
MeCO2Et
BrO
OEt
3 equiv 85%2
Ir(ppy)3
mono
di
tri
tetra
penta
Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
5 (0.375 mol%)
NaHCO3, DMAblue LED
K2PtCl4
NH
Me
NH
MeCO2Et
BrO
OEt
3 equiv "reaction proceeded efficiently"2
IrIIIN
N
NBr
O
OEt
3 equiv
NaOAc 3 equiv
CH2Cl2, blue LEDIrIII
N
N
NIrIII
N
N
N
5
35% 29%
O
EtO
Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
IrIIIN
N
N
photocatalyst
NaHCO3, DMAblue LED
NH
Me
NH
MeCO2Et
BrO
OEt
3 equiv2
IrIIIN
N
N
Me
Me
Me
0.187 mol%, 18 h 0.187 mol%, 18 h72% 94%
IrIV/III = +0.77 V
IrIIIN
N
N
0.187 mol%, 48 h<50%
IrIV/III = +0.49 V
Me
Me
Me
Me
Me
Me
Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
N
Ru(bpy)32+
1CT
3CT
λmax = 453 nm
Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
N
Ru(bpy)32+
1CT
3CT
excitation
λmax = 453 nm
Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803. Bernhard, S. Chem. Eur. J. 2007, 13 , 8726.
Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
N
Ru(bpy)32+
1CT
3CT
excitation
ISC
λmax = 453 nm
Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803. Bernhard, S. Chem. Eur. J. 2007, 13 , 8726.
Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
N
Ru(bpy)32+
1CT
3CT
3d-d
excitation
ISC
thermalactivation
in absence of quencher, thermal
equilibration to 3d-d state can occur
Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
N
Ru(bpy)32+
1CT
3CT
3d-d
excitation
ISC
thermalactivation
in 3d-d state, an antibonding
metal-based orbital is populated.
significant distortion of Ru–N bonds!
Durham, B.; Caspar, J. V.; Nagle, K. J.; Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
NRuII
NN
NN N
N
RuII
NN
NN
X
N
N
RuII
NN
NN
X
X
dissociative mechanism
(no entering group dependence for Ru(bpy)2(py)22+)
*Ru(bpy)32+
3d-d state
strong-field d6
+ X– + X–
RuII
NN
NN
N
NRuII
NN
NN
X
X
+ 2X–
X– = Cl–, Br–, NCS–
Durham, B.; Caspar, J. V.; Nagle, K. J.; Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
NRuII
NN
NN N
N
RuII
NN
NN
X
N
N
RuII
NN
NN
X
X
dissociative mechanism
(no entering group dependence for Ru(bpy)2(py)22+)
*Ru(bpy)32+
3d-d statestrong-field d6
complex φp (presence of O2) φp (degassed)
[Ru(bpy)3](NCS)2
[Ru(bpy)3](Cl)2
0.039 0.068
0.062 0.100
+ X– + X–
Durham, B.; Caspar, J. V.; Nagle, K. J.; Meyer, T. J. J. Am. Chem. Soc. 1982, 104 , 4803.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
RuII
NN
NN
N
N
[Ru(bpy)3]Br2
λmax = 453 nm
RuII
NN
NN
Br
Br
Ru(bpy)2Br2
λmax = 548 nm
hν
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
Ru
Ir
44
77
Electronegativity (EN)Ligand Field Stabilization Energy (LFSE)
Spin-Orbit Coupling (SO)
EN LFSE SO
increased ligand field stabilization energy makes it more difficult to
populate antibonding 3d-d state, so Ir complexes are more stable
than the corresponding Ru complexes
Tinker, L. T.; McDaniel, N. D.; Curtin, P. N.; Smith, C. K.; Ireland, M. J.; Bernhard, S. Chem. Eur. J. 2007, 13 , 8726.
Deactivation Pathways in Transition Metal CatalysisPhotoredox Catalysis
IrIII
N
N
N
N
+
Ir(ppy)2(bpy)PF6
9:3:1 MeCN:H2O:TEOA
K2PtCl4
H2H2O
IrIII
N
N
L
L
+
no d → π*N^N 3MLCT state!
Lowry, M. S.; Bernhard, S. Chem. Eur. J. 2006, 12 , 7970.
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
IrIII
N
N
N
N
+
–
Deactivation Pathways in Transition Metal Catalysis
reference
Photoredox Catalysis
IrIII
N
N
N
N
+
IrIII
N
N
L
L
+
n decomposition by loss of bpy is slow at high quencher concentration
n coordinating anions and low dielectric solvents accelerate decomposition
n high temperature results in more thermal crossing to 3d-d state
Poater, A.; Cavallo, L. Theor. Chem. Acc. 2012, 131 , 1155.
Deactivation Pathways in Transition Metal CatalysisWhy Study Catalyst Decomposition?
active for
catalysis
inactive for
catalysis
decomposition
"One of the reasons for [the] limited understanding [of catalyst deactivation] is that academic groups usually focus on the more rewarding improvement of activity and/or selectivity of a catalyst, since more or less rational strategies
can be followed, rather than investing resources to follow catalyst deactivation along unexplored pathways."