Nonplanarity of Tetrafluorocyclobutadiene

Petersson, E. J.; Fanuele, Jason; Nimlos, Mark R.; Lemal, David M.; Ellison, G. Barney; Radziszewski, Juliusz G.

doi:10.1021/ja971930u

Cited by 19 publications

(28 citation statements)

References 16 publications

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“…[11,12] For the phenylenes, reduction of p-antiaromatic overlap, which has been implicated as dominating the electronic interactions within the molecules, [4j] may be an additional driving force for deplanarization. The deviation from planarity of tetrafluorocyclobutadiene [13] and the cyclobutadiene dication [14] is noteworthy in this regard. The preference of the benzene nuclei in the phenylenes to adopt a planar configuration might, on first sight, be expected to oppose the deplanarizing influence of the fused cyclo-butadienes.…”

Section: Introductionmentioning

confidence: 93%

On the Nature of Nonplanarity in the [N]Phenylenes

et al. 1999

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The [N]phenylenes display marked deformation from planarity in the crystalline state. In order to probe the generality of this phenomenon, several derivatives were synthesized and their single-crystal X-ray structures were obtained. All new compounds displayed some degree of nonplanarity. Thus, for example, the parent triangular [4]phenylene (4 b) has a median bend angle at the ring junction of 1.58 and a range of 0.38 to 3.58, whereas hexakis[triisopropylsilyl(ethynyl)] triangular [4]phenylene (4 c) possesses the bulkiest appendages and the largest median bend angle and range (3.88 and 1.78 ± 5.68, respectively). A detailed analysis of the bending and twisting angles at the ring junctions, however, revealed that the magnitude of deformations were independent of topology, molecular size, and substituent type. In contrast to the phenylenes, a Cambridge Structural Database (CSD) search of unsubstituted and non-peri-substituted naphthalenes and anthracenes shows these molecules to be virtually planar in the solid state. A comparison of the single-point energies (HF/6-31G*) of the phenylenes with the acenes calculated for molecules possessing a fixed bend angle at the ring fusion of 38, 68, 98, and 128 reveals the former to be 26 % to 45 % easier to deform than the latter. Based on these results, the nonplanarity seen for the phenylenes is most likely a consequence of crystalpacking forces deforming particularly flexible molecules.

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Section: Introductionmentioning

confidence: 93%

On the Nature of Nonplanarity in the [N]Phenylenes

et al. 1999

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“…In addition, calculations showed that the phenylenes are more deformable than their hexagonal squeezes [37]. This flexibility was ascribed to ready pyramidalization of the four-membered ring carbons as a result of two phenomena: hyperconjugation of the low lying s antibonding orbitals of the strained bonds with the HOMO of the p system [114] and minimization of antiaromatic overlap in the cyclobutadiene nuclei [115]. The observation of such facile deplanarization is encouraging in view of projected syntheses of archimedene [53,70] and circular [5]phenylene (the phenylene analog of corannulene) [53].…”

Section: Structural Propertiesmentioning

confidence: 99%

[ N ]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbon

Miljanić

Vollhardt

2006

Carbon‐Rich Compounds

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“…Why is perfluorocyclobutadiene nonplanar? − Petersson et al first discovered the unexpected C 2 h symmetry of C 4 F 4 , by observing a 595 cm −1 ring-puckering mode with negative dichroism in its vibrational spectrum; this would be IR inactive in D 2 h symmetry. Their computed 11.6° out-of-plane angles of the C−F bonds (B3LYP/cc-pVDZ) result in substantial FCCF staggering across the single CC bonds (see Figure ).…”

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confidence: 99%

Why Are Perfluorocyclobutadiene and Some Other (CF)_n^q Rings Non-Planar?

Evangelista

Schleyer

2010

Org. Lett.

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Although surprising, the nonplanarity of C(2h) C(4)F(4) is not unique. While C(6)F(6) is planar, other members of the (CF)(n) family, for example, C(5)F(5)(-), C(6)F(6)(-), C(7)F(7)(-), and triplet C(7)F(7)(-) are not. C(2h) C(4)F(4) is not aromatic, as claimed (see above), but its antiaromaticity is reduced relative to the planar D(2h) form due to decreased pi antibonding and enhanced cross-ring pi overlap. The nonplanar C(2h) geometry also benefits from the relief of repulsive FC-CF bond eclipsing interactions.

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Nonplanarity of Tetrafluorocyclobutadiene

Cited by 19 publications

References 16 publications

On the Nature of Nonplanarity in the [N]Phenylenes

On the Nature of Nonplanarity in the [N]Phenylenes

[ N ]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbon

Why Are Perfluorocyclobutadiene and Some Other (CF)_n^q Rings Non-Planar?

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Nonplanarity of Tetrafluorocyclobutadiene

Cited by 19 publications

References 16 publications

On the Nature of Nonplanarity in the [N]Phenylenes

On the Nature of Nonplanarity in the [N]Phenylenes

[ N ]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbon

Why Are Perfluorocyclobutadiene and Some Other (CF)nq Rings Non-Planar?

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Why Are Perfluorocyclobutadiene and Some Other (CF)_n^q Rings Non-Planar?