The Electronics of CH Activation by Energy Decomposition Analysis: From Transition Metals to Main-Group Metals

King, Clinton R.; Gustafson, Samantha J.; Ess, Daniel H.

doi:10.1007/430_2015_178

Cited by 5 publications

(5 citation statements)

References 65 publications

(59 reference statements)

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“…Using energy decomposition analysis, we previously highlighted the electrophilic nature of Tl III in alkane C−H activation transition states that results from the dominant interaction between the Tl III 6s LUMO and a filled C−H σ bond. 20 Our description of Tl III acetate complexes is also consistent with the report by Bickelhaupt, who showed that there is minimal d-orbital participation in bonding in maingroup complexes. 21 In this work three major Tl III complexes were examined: Tl III (OAc) 3 , (OAc) 2 Tl III (CH 3 ), and (OAc)Tl III (CH 3 ) 2 .…”

Section: ■ Results and Discussionsupporting

confidence: 91%

“…In contrast, high-oxidation-state Tl III complexes have a core d 10 electronic configuration with a low-energy empty 6s orbital that determines oxidation states and reactivity. Using energy decomposition analysis, we previously highlighted the electrophilic nature of Tl III in alkane C–H activation transition states that results from the dominant interaction between the Tl III 6s LUMO and a filled C–H σ bond . Our description of Tl III acetate complexes is also consistent with the report by Bickelhaupt, who showed that there is minimal d-orbital participation in bonding in main-group complexes …”

Section: Resultssupporting

confidence: 88%

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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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Section: ■ Results and Discussionsupporting

confidence: 91%

Section: Resultssupporting

confidence: 88%

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

Gustafson

Konnick²,

Periana

et al. 2018

Organometallics

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“…However, the general features of these orbital interactions suggest that this C−H activation transition state should be described as an electrophilic substitution similar to other transition-metal acetate transition states. It is also noteworthy that energy decomposition analysis suggests that the interaction between Tl III (TFA) 3 and ethane has nearly equal covalent (orbital) and electrostatic character, 88 which can be described by the partial charges shown in Scheme 8b.…”

Section: ■ Introductionmentioning

confidence: 99%

Contrasting Mechanisms and Reactivity of Tl(III), Hg(II), and Co(III) for Alkane C–H Functionalization

et al. 2015

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Activation and functionalization of alkane C–H bonds has historically been dominated by transition-metal complexes. Light alkanes can also be partially oxidized by sixth-row main-group compounds, such as TlIII(TFA)3 (TFA = trifluoroacetate). Here we present density-functional calculations which demonstrate that TlIII(TFA)3 oxidizes alkanes by closed-shell C–H activation and Tl–alkyl functionalization mechanisms. The discovery of a C–H activation pathway is surprising, because TlIII often oxidizes arene C–H bonds through an electron transfer mechanism and the transition-metal complex CoIII(TFA)3, with similar oxidation state and ligand coordination, oxidizes alkanes via an open-shell radical mechanism. Comparison of TlIII(TFA)3 to the transition-metal analogue IrIII(TFA)3 reveals that key to TlIII oxidation of alkanes is a moderate barrier for C–H bond activation that is lower in energy than open-shell pathways and a subsequent metal–alkyl functionalization reaction step with a very low barrier. Our calculations suggest that the high-spin ground state of CoIII(TFA)3 provides a low-energy open-shell decarboxylation pathway that leads to radical oxidation of alkanes, which is not available for the d10 TlIII(TFA)3 complex. The C–H activation pathway and transition state model provide a straightforward explanation for why TlIII(TFA)3 promotes alkane C–H bond activation but HgII(TFA)2 does not.

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“…In addition, these two complexes are predicted to have large barriers for methane dissociation (∼13 kcal mol −1 by the M05-2X results). Fluorinated phosphines are poorer donors to metal centers than analogous alkyl-substituted phosphines. , The computational result for complexes of the (CF 3 ) 2 PCH 2 P(CF 3 ) 2 and (CF 3 ) 2 PCF 2 P(CF 3 ) 2 phosphines is therefore consistent with our expectation that the methane complex 2 should be stabilized relative to the methyl/hydride complex 1 if the ancillary ligands are less electron-donating than those we previously studied experimentally; other theoretical studies also support this idea. − …”

Section: Discussionmentioning

confidence: 97%

Steric and Electronic Analyses of Ligand Effects on the Stability of σ-Methane Coordination Complexes: A DFT Study

et al. 2022

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Developing efficient catalysts for methane functionalization is a longstanding goal in inorganic chemistry. Here, we present theoretical calculations to support efforts to synthesize σmethane complexes that can be studied by NMR spectroscopy. The systems studied are osmium complexes of stoichiometry (C 5 R 5 )Os(diphosphine)(CH 3 )(H) + : when both cyclopentadienyl and diphosphine are relatively strong electron donors, the methyl/ hydride structure is in rapid equilibrium with its σ-methane tautomer at low temperatures, as shown experimentally some years ago. Here, using density functional theory, we examine how changing the steric and electronic properties of the ancillary cyclopentadienyl and diphosphine ligands affects the relative energies of the two tautomers, with the goal of identifying a ligand set for which the σ-methane structure, rather than the methyl/hydride form, is the predominant species in equilibrium. We also examine how varying the ancillary ligands affects the barrier for methane dissociation. The calculations suggest that osmium complexes bearing weakly donating and sterically undemanding ligands stabilize the σ-methane structure both relative to its methyl/hydride tautomer and toward dissociation of the methane ligand. More specifically, osmium σ-methane complexes of fluorinated diphosphines (CF 3 ) 2 PCH 2 P(CF 3 ) 2 and (CF 3 ) 2 PCF 2 P(CF 3 ) 2 are predicted to be stable enough to be observed by variable-temperature NMR spectroscopy.

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The Electronics of CH Activation by Energy Decomposition Analysis: From Transition Metals to Main-Group Metals

Cited by 5 publications

References 65 publications

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

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

Contrasting Mechanisms and Reactivity of Tl(III), Hg(II), and Co(III) for Alkane C–H Functionalization

Steric and Electronic Analyses of Ligand Effects on the Stability of σ-Methane Coordination Complexes: A DFT Study

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