Hydrogen- and Fluorine-Bridged Disilyl Cations and Their Use in Catalytic C−F Activation

Panisch, Robin; Bolte, Michael; Müller, Thomas

doi:10.1021/ja061800y

Cited by 259 publications

(169 citation statements)

References 42 publications

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“…20,21,22 This is illustrated by the notable reduction in peri-distance by 0.3-0.4 Å for cyclic 1,8-naphthalenediyl Figure 1). 9 Furthermore, the aforementioned proximity of the peri-atoms in peri-substituted systems allows compounds with a stabilizing bridging geometry to be formed (for example P, Q; Figure 2), 23,24 and specifically bidentate coordination to a metal centre to create a chelate ring (for example R). 25,26 Figure 2.…”

Section: Introductionmentioning

confidence: 99%

“…The stabilisation of large heteroatoms and groups in peri-substituted systems via weak attractive interactions, additional rigid backbone, bridging geometries and metal complexation. 17,18,19,[21][22][23][24][25][26] In the present study, we explore the relationship between attraction and repulsion occurring within sub-van der Waals distances in a number of sterically restricted peri-substituted systems.…”

Section: Introductionmentioning

confidence: 99%

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Sterically Encumbered Tin and Phosphorus peri-Substituted Acenaphthenes

et al. 2014

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sterically Encumbered Tin and Phosphorus peri-Substituted Acenaphthenes

et al. 2014

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“…On the other hand, the utilization of silylium ions as catalysts has also been an area of intense research interest and their catalytic activity has been examined in various reactions [11,12]. For example, the groups of Ozerov as well as Müller have independently reported the defluorination of fluoro-and perfluoro-alkyl groups by using silylium ions [13][14][15]. Moreover, Sawamura implemented a silylium ion as Lewis acid catalyst in Mukaiyama aldol and Diels-Alder reactions [16].…”

Section: Introductionmentioning

confidence: 99%

Facile Access to Stable Silylium Ions Stabilized by N-Heterocyclic Imines

2016

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Novel silylium ions with N-heterocyclic imines were successfully synthesized. The reaction of trimethylsilyl imidazolin-2-imine Me 3 SiNIPr (NIPr = bis(2,6-diisopropylphenyl)-imidazolin-2-imino) with B(C 6 F 5 ) 3 leads to dimeric imino-substituted silylium ions through a methyl group abstraction on the silicon atom. Meanwhile, the intermolecular imino-coordinated silylium ion is formed by using the less sterically crowded imine Me 3 SiNItBu (NItBu = bis(tert-butyl)-imidazolin-2-imino).

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“…Evidence of a symmetrical fluoronium ion as low-energy transition state was found in the condensed state when 1,8-bis(diphenylmethylium) naphthalenediyl dication was treated with Me 3 SiFe 2 − (4). A Sicontaining ring system involving fluoronium ion, analogous to naphthalenediyl dication system, has also been reported in the condensed state (5).…”

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confidence: 97%

Study of the fluoro- and chlorodimethylbutyl cations

Oláh

Prakash

Rasul

2013

Proc. Natl. Acad. Sci. U.S.A.

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A comparative study of the 2,3-dimethyl-3-fluoro-2-butyl cation and its chloro analog was carried out by the ab initio/GIAO-CCSD (T) (gauge invariant atomic orbital-coupled cluster with single, double, and perturbative triple excitation) method. The structures and 13 C NMR chemical shifts of the cations were calculated at the GIAO-CCSD(T)/tzp/dz//MP2/cc-pVTZ level. Bridged fluoronium ion 1, carbenium ion 2, and fluorocarbenium ion 3 were found to be minima on the potential energy surface. Bridged fluoronium ion 1, although a minimum on the potential energy surface, is 12.8 kcal/mol less stable than the open chain fluorobutyl cation 3. In contrast to the fluorinated ion, bridged chloronium ion 5 was found to be the lowest energy minimum being 10.6 kcal/mol more stable than ion 6 and 7.4 kcal/mol more stable than ion 7.carbocations | computational studies H alonium ions are an important class of onium ions (1). The role of alkene halonium ion as reaction intermediates in electrophilic addition of halogens to olefins is well recognized (1). A wide variety of chloronium, bromonium, and iodonium ions have been prepared as stable long-lived ions (1). Several studies on the fluorination of olefins have led to suggestion that only trivalent persistent fluorocarbenium ions are involved as intermediates (2). There was some suggestion (3) of the formation of bridged fluoronium ion in the condensed state. Evidence of a symmetrical fluoronium ion as low-energy transition state was found in the condensed state when 1,8-bis(diphenylmethylium) naphthalenediyl dication was treated with Me 3 SiFe 2 − (4). A Sicontaining ring system involving fluoronium ion, analogous to naphthalenediyl dication system, has also been reported in the condensed state (5).In an attempt to observe the tetramethylethylenefluoronium ion ii in solution, Olah and Bollinger (6) ionized 2,3-difluoro-2, 3-dimethylbutane in SbF 5 /SO 2 at −90°C. The 1 H NMR spectrum of the acid solution at −90°C showed a deshielded doublet at δ 3.10 (J = 11.0 Hz), indicating the formation of cationic species wherein all of the methyl groups were equivalent with a longrange proton fluorine coupling. In the 19 F NMR spectrum, the observed fluorine signal was deshielded by 31 ppm from the difluoro progenitor. On the basis of these data, it was suggested (6) that the ion obtained was the 2,3-dimethyl-3-fluoro-2-butyl cation (a fluorodimethylisopropylcarbenium ion) i, wherein the methyl groups become equivalent either by a fast intramolecular fluorine exchange or by methyl group shifts. The formation of a long-lived tetramethylethylenefluoronium ion ii was ruled out on the basis of comparison with model compounds. If equilibration of ion i occurred through rapid intramolecular fluorine exchange, one could invoke ii only as a noncontributing high-lying intermediate or a transition state (Scheme 1, path i). If the exchange involves rapid 1,2-methyl migrations, then the 3,3-dimethyl-2-fluoro-2-butyl cation [(1-fluoro-1-tert-butyl)ethyl cation] iii should be involved. These two possib...

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Hydrogen- and Fluorine-Bridged Disilyl Cations and Their Use in Catalytic C−F Activation

Cited by 259 publications

References 42 publications

Sterically Encumbered Tin and Phosphorus peri-Substituted Acenaphthenes

Sterically Encumbered Tin and Phosphorus peri-Substituted Acenaphthenes

Facile Access to Stable Silylium Ions Stabilized by N-Heterocyclic Imines

Study of the fluoro- and chlorodimethylbutyl cations

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