Deactivation Pathways in Transition Metal Catalysis
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1 Deactivation Pathways in Transition tal Catalysis Why Study Catalyst Decomposition? decomposition active for catalysis inactive for catalysis "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." Poater, A.; Cavallo,. Theor. Chem. Acc. 2012, 131, 1155.
2 Deactivation Pathways in Transition tal Catalysis Why Study Catalyst Decomposition? Deactivation is much more studied in industrial settings where low catalyst loadings are critical. What happens if you lose 10% of your catalyst each cycle? 5%? 2%? % Catalyst umber of Cycles Even a modest improvement can have a large effect on TO!
3 Deactivation Pathways in Transition tal Catalysis Why 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.. Chem. Rev. 2015, 115, 127.
4 Deactivation Pathways in Transition tal Catalysis A Scarce Topic in the iterature igand loss or deleterious functionalization M M Multimetallic processes, cluster formation n Pd(0) Catalyst poisons C CO thiols O 2 Substrate or product inhibition O Br Crabtree, R.. Chem. Rev. 2015, 115, 127.
5 Deactivation Pathways in Transition tal Catalysis Outline ydrogenation Cross tathesis otoredox 2+ 2 Ir Cy 3 P 2 Ir Ir 2 2+ Ir III
6 Deactivation Pathways in Transition tal Catalysis Crabtree's Catalyst + Crabtree's Catalyst Ir n discovered in 1977 n reactivity for tetrasubstituted olefins TOF (mol substrate per mol cat. per hour) catalyst Rh(P 3 ) 3 [Rh(cod)(P 3 ) 2 ]PF 6 [Ir(cod) (py)]pf Xu, Y.; Mingos, M. P.; Brown, J. M. Chem. Commun. 2008, 199.
7 Deactivation Pathways in Transition tal Catalysis Crabtree's Catalyst + Ir A B A B C D 2, C 2 2 C D O O CO 2 CO 2 20 mol% cat, 99:1 dr 2 mol% cat, 89:11 dr Brown, J. M. Angew. Chem. Int. Ed. Engl. 1987, 26, 190.
8 Deactivation Pathways in Transition tal Catalysis Crabtree's Catalyst 2 3 C C 3 py S Ir S S 3 C C 3 py S Ir 2 S py Ir S Ir I /Ir III py Ir S py Ir Ir III /Ir V py Ir reductive elimination py Ir S migratory insertion reductive elimination py Ir migratory insertion Verendel, J. J.; Pàmies, O.; Diéguez, M.; Andersson, P. G. Chem. Rev. 2014, 114, 2130.
9 Deactivation Pathways in Transition tal Catalysis Crabtree's Catalyst 2 3 C C 3 py S Ir S S 3 C C 3 py S Ir 2 S py Ir S Ir I /Ir III py Ir S py Ir Ir III /Ir V py Ir reductive elimination py Ir S migratory insertion reductive elimination py Ir migratory insertion Verendel, J. J.; Pàmies, O.; Diéguez, M.; Andersson, P. G. Chem. Rev. 2014, 114, 2130.
10 Deactivation Pathways in Transition tal Catalysis Crabtree's Catalyst + K 2 Pt 4 2+ Ir 2, C 2 2 low [alkene] 2 Ir Cy 3 P 2 Ir Ir 2 n bulkier ligands can prevent trimerisation through steric hindrance n low catalyst concentration can prevent trimerisation n complexes with BAr F counterion rather than PF 6 are less moisture sensitive Xu, Y.; Mingos, M. P.; Brown, J. M. Chem. Commun. 2008, 199.
11 Deactivation Pathways in Transition tal Catalysis Crabtree's Catalyst + X O o-tol o-tol P Ir O tbu O 2, C 2 2 X mol% cat. conditions conversion % PF 6 4% 57% PF 6 4% rigorously dry 99% BAr F 0.3% 99% n complexes with BAr F counterion rather than PF 6 are less moisture sensitive ightfoot, A.; Schnider, P.; Pfaltz, A. Angew. Chem. Int. Ed. 1998, 37, 2897.
12 Deactivation Pathways in Transition tal Catalysis Outline ydrogenation Cross tathesis otoredox 2+ 2 Ir Cy 3 P 2 Ir Ir 2 2+ Ir III
13 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts EtO 2 C CO 2 Et metathesis cat. EtO 2 C CO 2 Et Schrock Chauvin Grubbs
14 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts unstable to: n coordinating solvents (C, DMSO, etc.) n lewis basic functionality Grubbs generation I n amines in particular 2 10 minutes 2 [] unidentified, inactive byproducts Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
15 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts 2 10 minutes 2 [] unidentified, inactive byproducts Bimolecular Catalyst Decomposition R R R R products Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
16 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts P O P O ipr PCy 2 ipr ipr widely studied 2 e spectator ligand sterically and electronically tunable strong σ-donor, weak π-acceptor very tight binding to metal sterically large ligand Crabtree, R.. J. Organomet. Chem. 2005, 690, 5451.
17 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts s s Functional Group Tolerance R O O O R O R O O R R O R R O R O R Trnka, T. M.; Grubbs, R.. Acc. Chem. Res. 2001, 34, 18.
18 Deactivation Pathways in Transition tal Catalysis Olefin thathesis Catalysts s s s s EtO 2 C CO 2 Et RCM ROMP Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
19 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts s s s s EtO 2 C CO 2 Et bulky ROMP small RCM Moore, J. S. et. al. Adv. Synth. Catal. 2009, 351, 1817.
20 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts s s 1 mol% ipro amine (n mol%), 60 ºC, 24 h Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
21 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts Benzylidene abstraction s s 2 R s s s 2 R R s + s s Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
22 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts ummiss, J. A. M.' Mcennan, W..; McDonald, R.; Fogg, D. E. Organometallics 2014, 33, 6738.
23 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts Benzylidene abstraction s s 2 R s s s 2 R R s + s s Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
24 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts Benzylidene abstraction s s 2 R s s s 2 R R s + s s tallacyclobutane deprotonation 2 Is R 2 Is R R 3 2 Is R R 3 + R decomp. Ireland, B. J.; Dobigny, B. T.; Fogg, D. E. ACS Catal. 2015, 5, 4690.
25 Deactivation Pathways in Transition tal Catalysis Olefin thathesis Catalysts E E metathesis catalyst E E C 2 2, 24 h s s O yield = 0% yield = 76% yield = >95% ong, S..; Chlenov, A.; Day, M. W.; Grubbs, R.. Angew. Chem. Int. Ed. 2007, 46, 5148.
26 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts E E metathesis catalyst E E C 2 2, 24 h s s O yield = 0% yield = 76% yield = >95% ong, S..; Chlenov, A.; Day, M. W.; Grubbs, R.. Angew. Chem. Int. Ed. 2007, 46, 5148.
27 Deactivation Pathways in Transition tal Catalysis Olefin thathesis Catalysts 40 ºC C 2 2, 12 h 24% 38% ong, S..; Chlenov, A.; Day, M. W.; Grubbs, R.. Angew. Chem. Int. Ed. 2007, 46, 5148.
28 Deactivation Pathways in Transition tal Catalysis Olefin thathesis Catalysts C activation hydride insertion R.E. 40 ºC C 2 2, > 7 days no reaction ong, S..; Chlenov, A.; Day, M. W.; Grubbs, R.. Angew. Chem. Int. Ed. 2007, 46, 5148.
29 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts 1.2 equiv C 2 2, 36 h + quantitative assistance required for second C insertion ong, S..; Chlenov, A.; Day, M. W.; Grubbs, R.. Angew. Chem. Int. Ed. 2007, 46, 5148.
30 Deactivation Pathways in Transition tal Catalysis Olefin thathesis Catalysts E E metathesis catalyst E E C 2 2, 24 h s s O yield = 0% yield = 76% yield = >95% ong, S..; Chlenov, A.; Day, M. W.; Grubbs, R.. Angew. Chem. Int. Ed. 2007, 46, 5148.
31 Deactivation Pathways in Transition tal Catalysis Olefin tathesis Catalysts s s A metathesis catalyst that tolerates free amines has yet to be reported.
32 Deactivation Pathways in Transition tal Catalysis Outline ydrogenation Cross tathesis otoredox 2+ 2 Ir Cy 3 P 2 Ir Ir 2 2+ Ir III
33 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis Ir III most organic molecules photoredox catalysts absorb light from ordinary light bulbs UV light Visible light 200 nm 300 nm 400 nm 500 nm 600 nm 700 nm Targeted delivery of energy via selective excitation of photoredox catalyst
34 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis Ir III otons converted into ~55 kcal/mol chemical potential energy Typical reaction: oxidation or reduction otoredox reaction: oxidation and reduction ew paradigm for reaction development
35 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis O Ir(ppy) 3 (0.375 mol%) CO 2 Et Br OEt aco 3, DMA blue ED 2 3 equiv 85% Ir III 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.
36 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis O O Et CO 2 Et Ir IV oxidant O SET Br O Et otoredox Catalytic Cycle SET * Ir III reductant Ir III CO 2 Et + CO 2 Et visible light reference Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
37 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis O Ir(ppy) 3 (0.375 mol%) CO 2 Et Br OEt aco 3, DMA blue ED 2 3 equiv 85% Ir III 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.
38 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis O Ir(ppy) 3 (0.375 mol%) CO 2 Et Br OEt aco 3, DMA blue ED 2 3 equiv 85% Ir III Ir(ppy) 3 Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
39 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis O Ir(ppy) 3 (0.375 mol%) CO 2 Et Br OEt aco 3, DMA blue ED 2 3 equiv 85% tri Ir III di tetra mono penta Ir(ppy) 3 Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
40 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis Ir III Br O 3 equiv OEt aoac 3 equiv C 2 2, blue ED Ir III EtO O Ir III 35% 29% 5 O K 2 Pt 4 5 (0.375 mol%) CO 2 Et Br OEt aco 3, DMA blue ED 2 3 equiv "reaction proceeded efficiently" Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
41 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis O photocatalyst CO 2 Et Br OEt aco 3, DMA blue ED 2 3 equiv Ir III Ir III Ir III mol%, 18 h mol%, 18 h 72% 94% Ir IV/III = V mol%, 48 h <50% Ir IV/III = V Stephenson, C. R. J. et al. Chem. Sci. 2015, 6, 537.
42 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis 1 CT 3 CT II λ max = 453 nm (bpy) 3 2+ reference yer, T. J. J. Am. Chem. Soc. 1982, 104, 4803.
43 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis 1 CT 3 CT II excitation λ max = 453 nm (bpy) 3 2+ reference yer, T. J. J. Am. Chem. yer, Soc. T. 1982, J. J. Am. 104, Chem Soc. Bernhard, 1982, 104, S. Chem Eur. J. 2007, 13, 8726.
44 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis 1 CT 3 CT II ISC excitation λ max = 453 nm (bpy) 3 2+ reference yer, T. J. J. Am. Chem. yer, Soc. T. 1982, J. J. Am. 104, Chem Soc. Bernhard, 1982, 104, S. Chem Eur. J. 2007, 13, 8726.
45 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis 1 CT II 3 CT ISC thermal activation 3 d-d excitation in absence of quencher, thermal equilibration to 3 d-d state can occur (bpy) 3 2+ reference yer, T. J. J. Am. Chem. Soc. 1982, 104, 4803.
46 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis 1 CT II 3 CT ISC thermal activation 3 d-d excitation in 3 d-d state, an antibonding metal-based orbital is populated. (bpy) 3 2+ significant distortion of bonds! reference yer, T. J. J. Am. Chem. Soc. 1982, 104, 4803.
47 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis II II + X X + X II II X X *(bpy) d-d state dissociative mechanism (no entering group dependence for (bpy) 2 (py) 2 2+ ) strong-field d 6 II + 2X II X X X =, Br, CS reference Durham, B.; Caspar, J. V.; agle, K. J.; yer, T. J. J. Am. Chem. Soc. 1982, 104, 4803.
48 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis II II + X X + X II II X X *(bpy) d-d state dissociative mechanism (no entering group dependence for (bpy) 2 (py) 2 2+ ) strong-field d 6 complex φ p (presence of O 2 ) φ p (degassed) [(bpy) 3 ](CS) 2 [(bpy) 3 ]() reference Durham, B.; Caspar, J. V.; agle, K. J.; yer, T. J. J. Am. Chem. Soc. 1982, 104, 4803.
49 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis II hν II Br Br [(bpy) 3 ]Br 2 (bpy) 2 Br 2 λ max = 453 nm λ max = 548 nm reference Durham, B.; Caspar, J. V.; agle, K. J.; yer, T. J. J. Am. Chem. Soc. 1982, 104, 4803.
50 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis 44 E FSE SO 77 Ir Electronegativity (E) igand Field Stabilization Energy (FSE) Spin-Orbit Coupling (SO) increased ligand field stabilization energy makes it more difficult to populate antibonding 3 d-d state, so Ir complexes are more stable than the corresponding complexes
51 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis K 2 Pt 4 2 O Ir(ppy) 2 (bpy)pf 6 9:3:1 C: 2 O:TEOA Ir III Ir III no d π* ^ 3 MCT state! Tinker,. T.; McDaniel,. D.; Curtin, P..; Smith, C. K.; Ireland, M. J.; Bernhard, S. Chem. Eur. J. 2007, 13, 8726.
52 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis + Ir III reference owry, M. S.; Bernhard, S. Chem. Eur. J. 2006, 12, 7970.
53 Deactivation Pathways in Transition tal Catalysis otoredox Catalysis + + Ir III Ir III 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 3 d-d state reference
54 Deactivation Pathways in Transition tal Catalysis Why Study Catalyst Decomposition? decomposition active for catalysis inactive for catalysis "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." Poater, A.; Cavallo,. Theor. Chem. Acc. 2012, 131, 1155.
deactivation or decomposition is therefore quantified using the turnover number.
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