Fluoronium metathesis and rearrangements of fluorine-stabilized carbocations

Morton, Thomas Hellman

doi:10.1016/j.ijms.2011.07.024

Cited by 5 publications

(5 citation statements)

References 38 publications

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“…Local modes are perfectly suited to describe the strength of CX bonds in a quantitative rather than just qualitative way. The information gained in this way provides an important insight into the structure, stability, and reactivity of CX containing compounds, which are relevant in many areas of chemistry ranging from synthesis, spectroscopy, reaction mechanism, and reaction dynamics to astrochemistry …”

Section: Introductionmentioning

confidence: 99%

“…The stabilization of carbenium ions by α‐halogen substituents is even stronger . Therefore, the thermochemistry of these molecules and halogen stabilization energies have been thoroughly investigated by Raabe et al Spectroscopic evidence for partial CF double bonding in carbenium ions was reported by Morton and coworkers and quantum chemically confirmed by Kraka and Cremer . In these ions, the halogen becomes positively charged and (partially) establishes double bond.…”

Section: Introductionmentioning

confidence: 99%

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Are carbon—halogen double and triple bonds possible?

Kalescky

Kraka

Cremer

2014

Int J of Quantum Chemistry

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The carbonAhalogen and carbonAchalcogen bonding of 84 molecules was investigated utilizing local vibrational modes calculated at the M06-2X/cc-pVTZ level of theory including anharmonicity corrections in all cases. The relative bond strength order of each CX or CE bond (X 5 F, Cl; E 5 O, S) was derived from the local CX or CE stretching force constant and compared with trends of calculated bond lengths r and bond dissociation energies (BDE) obtained at the G3 level of theory. It is shown that both bond length r and BDE are not reliable bond strength descriptors. The CX double bond is realized for some Cl-substituted carbenium ions, however, not for the cor-responding F-derivatives. Diatomic CF 1 and CCl 1 possess fully developed double bonds but not, as suggested in the literature, triple bonds. Halonium ions have fractional (electron-deficient) CX bonds, which can be stabilized by r-donor substituents or by an increased polarizability of the halogen atom as with Cl. Bridged halonium ions are more stable than their acyclic counterparts, which results from more effective two-electron-three-center bonding.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Are carbon—halogen double and triple bonds possible?

Kalescky

Kraka

Cremer

2014

Int J of Quantum Chemistry

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“…Several new classes of compounds containing multiple bonds between carbon and another main-group atom have been recently discovered, but so far are limited to elements from main-groups 13 to 16. , Few examples of simple molecules with multiple bonds involving carbon and a halogen X atom (X = F, Cl) are the diatomic CX + molecules. However, there is still no consensus about their bond orders. − Spectroscopic and computational studies on the nature of C–X bonds of halogen-stabilized carbocations found that the halogen atom becomes positively charged, partially establishing a double bond. In particular, Cremer and co-workers reported that a C–X double bond is fully developed for some Cl-substituted carbenium ions, such as CCl + but not for the corresponding F-derivatives .…”

Section: Introductionmentioning

confidence: 99%

Doubly and Triply Charged Species Formed from Chlorobenzene Reveal Unusual C–Cl Multiple Bonding

et al. 2018

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In free-radical halogenation of aromatics, singly charged ions are usually formed as intermediates. These stable species can be easily observed by time-of-flight mass spectrometry (TOF-MS). Here we used electron and proton beams to ionize chlorobenzene (CHCl) and investigate the ions stability by TOF-MS. Additionally to the singly charged parent ion and its fragments, we find a significant yield of doubly and triply charged parent ions not previously reported. In order to characterize these species, we used high-level theoretical methods based on density functional theory (DFT), coupled-cluster (CC), and generalized valence bond (GVB) to calculate the structure, relative stabilities, and bonding of these dications and trications. The most stable isomers exhibit unusual carbon-chlorine multiple bonding: a terminal C═Cl double bond in a formyl-like CHCl moiety (1, r = 1.621 Å) and a ketene-like C═C═Cl cumulated species (2, r = 1.542 Å). The calculations suggest that an excited state of 2 has a nitrile-like C≡Cl triple bond structure.

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“…Because halogen has a valence of 1, chemistry traditionally considers any bond multiplicity higher than 1 for halogen–carbon bonds to be less likely . However, there have been a number of studies in the literature that suggest some variation in the CX single-bond character. − …”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the existence of a + CX double bond or even a triple bond as in the diatomic + CX is more than questionable. Knowledge of the CX bonding mechanism is desirable in many areas of chemistry ranging from synthesis, thermochemistry, spectroscopy, ,, reaction mechanism, and reaction dynamics ,− to fields such as astrochemistry …”

Section: Introductionmentioning

confidence: 99%

Quantitative Assessment of the Multiplicity of Carbon–Halogen Bonds: Carbenium and Halonium Ions with F, Cl, Br, and I

2014

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CX (X = F, Cl, Br, I) and CE bonding (E = O, S, Se, Te) was investigated for a test set of 168 molecules using the local CX and CE stretching force constants k(a) calculated at the M06-2X/cc-pVTZ level of theory. The stretching force constants were used to derive a relative bond strength order (RBSO) parameter n. As alternative bond strength descriptors, bond dissociation energies (BDE) were calculated at the G3 level or at the two-component NESC (normalized elimination of the small component)/CCSD(T) level of theory for molecules with X = Br, I or E = Se, Te. RBSO values reveal that both bond lengths and BDE values are less useful when a quantification of the bond strength is needed. CX double bonds can be realized for Br- or I-substituted carbenium ions where as suitable reference the double bond of the corresponding formaldehyde homologue is used. A triple bond cannot be realized in this way as the diatomic CX(+) ions with a limited π-donor capacity for X are just double-bonded. The stability of halonium ions increases with the atomic number of X, which is reflected by a strengthening of the fractional (electron-deficient) CX bonds. An additional stability increase of up to 25 kcal/mol (X = I) is obtained when the X(+) ion can form a bridged halonium ion with ethene such that a more efficient 2-electron-3-center bonding situation is created.

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Fluoronium metathesis and rearrangements of fluorine-stabilized carbocations

Cited by 5 publications

References 38 publications

Are carbon—halogen double and triple bonds possible?

Are carbon—halogen double and triple bonds possible?

Doubly and Triply Charged Species Formed from Chlorobenzene Reveal Unusual C–Cl Multiple Bonding

Quantitative Assessment of the Multiplicity of Carbon–Halogen Bonds: Carbenium and Halonium Ions with F, Cl, Br, and I

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