Arene C–H Functionalization by p-Block Metal Tl(III) Occurs at the Borderline of C–H Activation and Electron Transfer

King, Clinton R.; Gustafson, Samantha J.; Black, Benjamin R.; Butler, Steven; Konnick, Michael M.; Periana, Roy A.; Hashiguchi, Brian M.; Ess, Daniel H.

doi:10.1021/acs.organomet.6b00475

Cited by 9 publications

(7 citation statements)

References 47 publications

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“…Hammett analysis of (bpy)Ni II (Ar)Br arene electronics yielded a shallow, negative slope (ρ + = −0.87) vs σ + , consistent with a development of positive charge on the arene in the transition state and a more electrophilic carbon. This shallow slope more closely resembles that found in the Blum arylgold(I) concerted PDM (ρ + = −0.41) than that found in the Kozlowski stepwise PDM where the steeper slope supports a formally charged Wheland intermediate (ρ + = −4.0) …”

Section: Discussionsupporting

confidence: 75%

Protodemetalation of (Bipyridyl)Ni(II)–Aryl Complexes Shows Evidence for Five-, Six-, and Seven-Membered Cyclic Pathways

et al. 2023

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Protonation of C−M bonds and its microscopic reverse, metalation of C−H bonds, are fundamental steps in a variety of metal-catalyzed processes. As such, studies on protonation of C−M bonds can shed light on C−H activation. We present here studies on the rate of protodemetalation (PDM) of a suite of arylnickel(II) complexes with various acids that provide evidence for a concerted, cyclic transition state for the PDM of C−Ni bonds and demonstrate that five-, six-, and seven-membered transition states are particularly favorable. Our data show that while the rate of protodemetalation of arylnickel(II) complexes scales with acidity for many acids, several are faster than predicted by pK a . For example, while acetic acid and acetohydroxamic acid are much less acidic than HCl, they both protodemetalate arylnickel(II) complexes significantly faster than HCl. Our data also show how in the case of acetohydroxamic acid, a seven-membered cyclic transition state (CH 3 C(O)NHOH) can be more favorable than a six-membered transition state (CH 3 C(O)NHOH). Similarly, five-membered transition states, such as for pyrazole, are highly favorable as well. Comparison of transition state polarization (from density functional theory) compares these new nickel transition states to betterstudied precious-metal systems and demonstrates how the base can change the polarization of the transition state giving rise to opposing electronic preferences. Collectively, these studies suggest several new avenues for study in C−H activation as well as approaches to accelerate or slow protodemetalation in nickel catalysis.

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Section: Discussionsupporting

confidence: 75%

Protodemetalation of (Bipyridyl)Ni(II)–Aryl Complexes Shows Evidence for Five-, Six-, and Seven-Membered Cyclic Pathways

et al. 2023

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“…However, our density functional theory (DFT) calculations, coupled with experimental studies, provided evidence that Tl III (TFA) 3 oxidizes light alkanes by a closed-shell electrophilic C–H activation and one-step metal–alkyl functionalization mechanism (Scheme b), which is similar to our DFT-based mechanistic proposal for Hg II -catalyzed methane functionalization in sulfuric acid . We also discovered that the reaction of benzene with Tl III (TFA) 3 to give (TFA) 2 Tl III (Ph) also involves a C–H activation mechanism rather than a S E Ar mechanism with a dearomatized Wheland-type intermediate …”

Section: Introductionsupporting

confidence: 73%

“…10 We also discovered that the reaction of benzene with Tl III (TFA) 3 to give (TFA) 2 Tl III (Ph) also involves a C−H activation mechanism rather than a S E Ar mechanism with a dearomatized Wheland-type intermediate. 11 Functionalization of Tl III −alkyl bonds also occurs in water solvent. 12 For example, at ∼100 °C (OAc) 2 Tl III (CH 3 ) (OAc = acetate) dissolved in water results in two-electron reductive functionalization of the Tl III −C bond to give Tl I (OAc), methyl acetate (MeOAc), and methanol (MeOH, Scheme 3a).…”

Section: ■ Introductionmentioning

confidence: 99%

Mechanisms and Reactivity of Tl(III) Main-Group-Metal–Alkyl Functionalization in Water

Gustafson

Konnick²,

Periana

et al. 2018

Organometallics

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Metal-mediated C–H activation reactions generate metal–alkyl intermediates that can be converted into carbon–oxygen bonds through functionalization reactions. While the mechanisms and reactivity of C–H activation reactions have been well studied for transition-metal complexes, much less is known about functionalization reactions, especially for main-group-metal–alkyl complexes. Here we report density functional theory calculations on the reaction thermodynamics and kinetic pathways for main-group, p-block-metal TlIII–methyl functionalization reactions in water using a combination of continuum and explicit/continuum solvent models. Specifically, we examined the oxygen functionalization of (OAc)TlIII(CH3)2 and (OAc)2TlIII(CH3) in water where in both cases functionalization gives methyl acetate and methanol. Our calculations suggest that (OAc)TlIII(CH3)2 is thermodynamically and kinetically stable against bond homolysis, heterolysis, protonolysis, and all reductive functionalization pathways. Functionalization is only possible after methyl anion group transfer to TlIII(OAc)3 to give (OAc)2TlIII(CH3). Our calculations suggest that this monomethyl structure is functionalized by acetate dissociation to give a Tl monocation and then a one-step nucleophilic functionalization where water and acetate have competitive transition states.

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“…If you think C–H bonds are tough, wait until you read Diaconescu and Huang’s work on C–F activation with rare-earth metals! Organometallic chemistry is further extended to the lanthanides in work from Rozenel, Perrin, Eisenstein, and Andersen, who report an elegant combination of experiment and theory involving classical metallocene systems of La and Ce, to understand how an amide is transformed into an enamide. Just when we thought we were finished with electrophilic metals, our special issue was fortunate to include a theoretical study by Ess and co-workers addressing the mechanism of action for arene C–H functionalization using the p-block complex Tl(TFA) 3 (TFA = trifluoroacetate) …”

mentioning

confidence: 99%

Foreword for the Special Issue “Hydrocarbon Chemistry: Activation and Beyond”. Responsible or Irresponsible Use of Hydrocarbons? You Be the Judge!

Mindiola

2017

Organometallics

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I n the process of choosing contributors for this special issue in Organometallics entitled "Hydrocarbon Chemistry: Activation and Beyond", we focused our attention on science that interfaced with the frontier areas of organometallic chemistry. Our target was to place special emphasis on organometallic applications that implicated novel transformations and catalysis with, but not limited to, hydrocarbons. This special issue highlights different approaches and synthetic strategies to target unique organometallic reagents as well as to understand C−X bond-activation or bond-making reactions that interface with energy-related transformations, especially those that hold promise in industry. This issue also interfaces homogeneous, heterogeneous, and theoretical communities, all sharing common interests in catalysis and the understanding of reaction mechanisms. As a result, this special issue captures some of the best content in organometallic chemistry involving the "responsible usage" of hydrocarbons. The meaning of the term "responsible" relates to the exploration of noncombustible processes that can better take advantage of the energy stored in these natural resources. We try to emphasize the importance of controlled C−H bond activation and functionalization in our cover art for this issue, as an alternative to the more detrimental (but simpler) process of combustion.With Guest Editors Christophe Copeŕet and Alan Goldman, we are privileged to showcase some of the most entertaining reactions involving M−C bonds, hydrocarbon activation, and hydrocarbon functionalization, as well as catalytic processes leading to their functionalization and/or coupling. It is notable to mention that early, mid, and late transition metals, in addition to main-group and lanthanide (and rare-earth) examples, are integral parts of this special issue with solid-, solution-, and gas-phase reactions being included.A well established pillar of organometallic chemistry has been the preparation of reactive metal−carbon bonds (or multiple bonds) that promote C−H activation reactions of hydrocarbons. 1−4 In this vein, is a series of papers involving the highly electropositive transition and lanthanide metal ions. Legzdins and co-workers 5,6 publish back-to-back manuscripts that describe the use of well-defined tungsten complexes that can activate and subsequently functionalize hydrocarbons (including methane). 7 Speaking of methane, one major impediment to utilization of this valuable resource is the limited understanding of its reactivity in the gas phase. Schwarz and co-workers 8 address this challenge in their combined experimental and theoretical study of the thermal gas-phase chemistry of CH 4 . By moving diagonally from tungsten to niobium compounds with strained organometallic ligands, Etienne and co-workers 9 report stereospecific C−H bond splitting reactions via a 1,3-CH addition process. 10 Cundari and Parveen 11 compliment some of the early-transition-metal chemistry by "theoretically" tuning Ta(III) systems that can undergo oxidation...

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Arene C–H Functionalization by p-Block Metal Tl(III) Occurs at the Borderline of C–H Activation and Electron Transfer

Cited by 9 publications

References 47 publications

Protodemetalation of (Bipyridyl)Ni(II)–Aryl Complexes Shows Evidence for Five-, Six-, and Seven-Membered Cyclic Pathways

Protodemetalation of (Bipyridyl)Ni(II)–Aryl Complexes Shows Evidence for Five-, Six-, and Seven-Membered Cyclic Pathways

Mechanisms and Reactivity of Tl(III) Main-Group-Metal–Alkyl Functionalization in Water

Foreword for the Special Issue “Hydrocarbon Chemistry: Activation and Beyond”. Responsible or Irresponsible Use of Hydrocarbons? You Be the Judge!

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