Mechanistic Aspects of C−H Activation by Pt Complexes

Lersch, Martin; Tilset, Mats

doi:10.1021/cr030710y

Cited by 734 publications

(465 citation statements)

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“…All three [(CH 3 )Pt(L)] + complexes are capable of activating methane in thermal ion/molecule reactions, as demonstrated by the occurrence of H/D exchange when using CD 4 . Of these complexes, [(CH 3 )Pt(py)] + with the monodendate pyridine as a ligand is about five times more reactive than the complexes with the bidentate nitrogen donors bipy and phen, which can be attributed to the lower coordination of the platinum center in [(CH 3 )Pt(py)] + .…”

Section: Discussionmentioning

confidence: 98%

“…While solution phase experiments have brought a wealth of knowledge about the activation of methane by transition metal complexes [4], gas phase experiments can provide a helpful complement to these approaches in revealing the details of the elementary steps involved in the activation of methane [5]. Particularly intriguing in this respect is a recent debate about the relevance of gas phase studies for reactions occurring in condensed media [6,7], which dealt with the C-H bond activation of benzene by cationic [(CH 3 )-Pt(L)] + complexes [8,9], where L corresponds to a 0932-0776 / 07 / 0300-0309 $ 06.00 © 2007 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com bidentate nitrogen ligand.…”

Section: Introductionmentioning

confidence: 99%

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C–H Bond Activation ofMethane with Gaseous [(CH₃)Pt(L)]⁺ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

Butschke

Schlangen

Schwarz

et al. 2007

Zeitschrift Für Naturforschung B

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+ also bring about activation of methane, though at a lower rate, whereas the bipyridine complex [(CH 3 )Pt(py) 2 ] + does not react with methane at thermal conditions. A detailed analysis of the experimental data by means of kinetic modeling provides insight into the underlying mechanistic steps, but a distinction whether the reaction occurs as σ bond metathesis or via an oxidative addition cannot be made on the basis of the experimental data available.

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Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

C–H Bond Activation ofMethane with Gaseous [(CH₃)Pt(L)]⁺ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

Butschke

Schlangen

Schwarz

et al. 2007

Zeitschrift Für Naturforschung B

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“…The 17 kcal/mol activation energy calculated for IO 4 -is remarkably low for a M-C to M-O-C transformation given the significant change in electronic configurations. However, this value is consistent with the facile reaction observed at room temperature.…”

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confidence: 88%

Facile Functionalization of a Metal Carbon Bond by O-Atom Transfer

et al. 2006

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A key challenge to developing selective, low-temperature hydrocarbon oxidation catalysts based on the CH activation reaction is integration with a compatible functionalization reaction. 1,2 We recently reported a CH activation reaction (Figure 1) with an alkoxo complex, M-OR, that simultaneously generates a functionalized product, ROH, and a metal alkyl, M-R, where M is Ir(III). 3a,b As shown in Figure 1, a catalytic cycle for the conversion of RH to ROH could be possible by regeneration of M-OR from M-R with O-atom donors, YO. Pt(IV) or Hg(II) alkyls are M-C σ+ polarized and readily undergo reductive functionalization with O-nucleophiles. 1b,4 However, M-Rs of more electropositive metals, such as Ir or Re, in the lower oxidation states useful for C-H activation do not undergo facile reductive functionalizations and are likely M-C σ-polarized. Consequently, functionalization of these M-Rs may be more facile in nonredox, insertion reactions with electrophilic YOs (Figure 1) if free-radical pathways or formal oxidation of the metal centers could be minimized. 5 Conversion of Y to YO with O 2 could complete the overall catalytic cycle for the overall oxidation of RH with O 2 .The conversion of M-R to M-OR is not well-known, and the few reported examples proceed with O 2 by free-radical pathways 6 or by slow redox reactions involving alkyl to metal oxo migration. 7 Consequently, identification of a facile pathway for this reaction, especially with non-peroxo 8 YOs that could potentially be recycled with O 2 , could be useful. We report here combined experimental and theoretical evidence for a facile Re-R to Re-OR bond conversion with non-peroxo YOs that proceeds via a low-energy, Baeyer-Villiger (BV)-type, electrophilic O-atom insertion.BV and alkyl borane oxidation reactions to generate oxyesters and alkoxy boranes, respectively, are well-known organic reactions involving electrophilic O-insertions with YOs. Significantly, both peroxo and non-peroxo YOs can be utilized, and the reactions proceed without free radicals or formal redox changes. 9 Methyltrioxorhenium, MTO, with peroxo YOs is well-known to catalyze olefin epoxidation and other oxidation reactions likely via Re η 2 -peroxo intermediates. 10 A reported observation that attracted our attention was that an undesirable side reaction is the decomposition of a MTO catalyst to methanol at room temperature. 11 We were intrigued because, despite the high Re(VII) oxidation state, unlike Pt(IV) alkyls, 1b,4 treatment of MTO in basic or acidic water does not generate Re(V) and methanol. Consistent with the observations of the initial investigators, 11 we find that the formation of methanol from MTO in water requires added H 2 O 2 as the oxidant. The reaction is facile, selective, quantitative, and significantly proceeds without a change in oxidation state of the Re to generate the ReO 4 -anion.In the initial studies on decomposition of MTO to methanol, only H 2 O 2 was investigated and two non-BV-type mechanisms proposed: reaction via a η 2 -peroxo intermediate or...

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“…40 Evidence for both types of process has been presented for platinum(II). 41 It is worth considering one 42 of these reports in more detail as it deals with the cycloplatination of a complex rather similar to ours: an o-tolylphosphine is coordinated to a dimethyl platinum centre that also has a DMSO ligand.…”

Section: A-d 2a-dmentioning

confidence: 99%

Platinum(ii) N-heterocyclic carbene complexes: coordination and cyclometallation.

et al. 2010

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Mechanistic Aspects of C−H Activation by Pt Complexes

Cited by 734 publications

References 310 publications

C–H Bond Activation ofMethane with Gaseous [(CH₃)Pt(L)]⁺ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

C–H Bond Activation ofMethane with Gaseous [(CH₃)Pt(L)]⁺ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

Facile Functionalization of a Metal Carbon Bond by O-Atom Transfer

Platinum(ii) N-heterocyclic carbene complexes: coordination and cyclometallation.

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Mechanistic Aspects of C−H Activation by Pt Complexes

Cited by 734 publications

References 310 publications

C–H Bond Activation ofMethane with Gaseous [(CH3)Pt(L)]+ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

C–H Bond Activation ofMethane with Gaseous [(CH3)Pt(L)]+ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

Facile Functionalization of a Metal Carbon Bond by O-Atom Transfer

Platinum(ii) N-heterocyclic carbene complexes: coordination and cyclometallation.

Contact Info

Product

Resources

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C–H Bond Activation ofMethane with Gaseous [(CH₃)Pt(L)]⁺ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)

C–H Bond Activation ofMethane with Gaseous [(CH₃)Pt(L)]⁺ Complexes (L = Pyridine, Bipyridine, and Phenanthroline)