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|a 10.1021/acs.organomet.3c00309
|2 doi
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|a pubmed24n1206.xml
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|a (DE-627)NLM362090459
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|a (NLM)37711884
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|a DE-627
|b ger
|c DE-627
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|a eng
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|a Platt, George M H
|e verfasserin
|4 aut
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|a Opening a Pandora's Flask on a Prototype Catalytic Direct Arylation Reaction of Pentafluorobenzene
|b The Ag2CO3/Pd(OAc)2/PPh3 System
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|c 2023
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|a Text
|b txt
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|a ƒaComputermedien
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|2 rdamedia
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|a ƒa Online-Ressource
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|a Date Revised 17.09.2023
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|a published: Electronic-eCollection
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|a Citation Status PubMed-not-MEDLINE
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|a © 2023 The Authors. Published by American Chemical Society.
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|a Direct C-H functionalization reactions have opened new avenues in catalysis, removing the need for prefunctionalization of at least one of the substrates. Although C-H functionalization catalyzed by palladium complexes in the presence of a base is generally considered to proceed by the CMD/AMLA-6 mechanism, recent research has shown that silver(I) salts, frequently used as bases, can function as C-H bond activators instead of (or in addition to) palladium(II). In this study, we examine the coupling of pentafluorobenzene 1 to 4-iodotoluene 2a (and its analogues) to form 4-(pentafluorophenyl)toluene 3a catalyzed by palladium(II) acetate with the commonplace PPh3 ligand, silver carbonate as base, and DMF as solvent. By studying the reaction of 1 with Ag2CO3/PPh3 and with isolated silver (triphenylphosphine) carbonate complexes, we show the formation of C-H activation products containing the Ag(C6F5)(PPh3)n unit. However, analysis is complicated by the lability of the Ag-PPh3 bond and the presence of multiple species in the solution. The speciation of palladium(II) is investigated by high-resolution-MAS NMR (chosen for its suitability for suspensions) with a substoichiometric catalyst, demonstrating the formation of an equilibrium mixture of Pd(Ar)(κ1-OAc)(PPh3)2 and [Pd(Ar)(μ-OAc)(PPh3)]2 as resting states (Ar = Ph, 4-tolyl). These two complexes react stoichiometrically with 1 to form coupling products. The catalytic reaction kinetics is investigated by in situ IR spectroscopy revealing a two-term rate law and dependence on [Pdtot/nPPh3]0.5 consistent with the dissociation of an off-cycle palladium dimer. The first term is independent of [1], whereas the second term is first order in [1]. The observed rates are very similar with Pd(PPh3)4, Pd(Ph)(κ1-OAc)(PPh3)2, and [Pd(Ph)(μ-OAc)(PPh3)]2 catalysts. The kinetic isotope effect varied significantly according to conditions. The multiple speciation of both AgI and PdII acts as a warning against specifying the catalytic cycles in detail. Moreover, the rapid dynamic interconversion of AgI species creates a level of complexity that has not been appreciated previously
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|a Journal Article
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1 |
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|a Aguiar, Pedro M
|e verfasserin
|4 aut
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| 700 |
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|a Athavan, Gayathri
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Bray, Joshua T W
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Scott, Neil W J
|e verfasserin
|4 aut
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| 700 |
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|a Fairlamb, Ian J S
|e verfasserin
|4 aut
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| 700 |
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|a Perutz, Robin N
|e verfasserin
|4 aut
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| 773 |
0 |
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|i Enthalten in
|t Organometallics
|d 1998
|g 42(2023), 17 vom: 11. Sept., Seite 2378-2394
|w (DE-627)NLM098167103
|x 0276-7333
|7 nnns
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| 773 |
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|g volume:42
|g year:2023
|g number:17
|g day:11
|g month:09
|g pages:2378-2394
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|u http://dx.doi.org/10.1021/acs.organomet.3c00309
|3 Volltext
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