Synthesis of pentaphenylborole, a potentially antiaromatic system

Eisch, John J.; Hota, N. K.; Kozima, Sinpei

doi:10.1021/ja01044a059

Cited by 197 publications

(135 citation statements)

References 6 publications

Supporting

Mentioning

131

Contrasting

Unclassified

Order By: Relevance

“…[11,12] All boroles were dissolved in dry, argon-saturated CH 2 Cl 2 with a concentration of the solution of 1-3 × 10 −3 mol/l. Because boroles decompose rapidly in the presence of air or moisture, all experiments were performed in an inert gas atmosphere.…”

Section: Sample Preparationmentioning

confidence: 99%

Probing antiaromaticity: resonance Raman investigation of a series of differently substituted boroles

Köhler

Lindenmeier

Fischer

et al. 2009

J Raman Spectroscopy

View full text Add to dashboard Cite

We report an investigation of four differently substituted boroles by resonance Raman (RR) spectroscopy with the aim of gaining insight into the structural changes that occur upon electronic π -π * excitation in the five-membered BC 4 ring. Such boroles are prototypes for the theory of antiaromaticity, because the empty p z orbital at the boron interacts with the π system of the carbon backbone to delocalize the four π electrons. The magnitude of this interaction depends on the substituents at the boron atom. In all compounds, an intense band appears around 1600 cm −1 , which can be assigned to a C C stretching vibration. The selective amplification of this mode indicates an expansion of the borole ring upon electronic excitation. The resonant enhancement of another mode at around 1300 cm −1 , which can be assigned to a vibration between the boron and the substituent, gives evidence that the degree of antiaromaticity in the borole depends strongly on the interaction between the substituent at the boron atom with the empty p z orbital of the boron. When the boron is connected to a ferrocene, this band appears with high intensity, indicating a strong interaction between B and Fe. Furthermore, we studied the dependence of the excitation wavelength on the Raman intensities. In addition, we used DFT calculations to determine the vibrational wavenumbers.

show abstract

Section: Sample Preparationmentioning

confidence: 99%

Probing antiaromaticity: resonance Raman investigation of a series of differently substituted boroles

Köhler

Lindenmeier

Fischer

et al. 2009

J Raman Spectroscopy

View full text Add to dashboard Cite

show abstract

“…[1] Starting in 1969, [2] when 1,2,3,4,5-pentaphenylborole (1) was isolated as the first of its kind, and increasing since its structural analysis in 2008, [3] a growing number of publications emphasizes the significance of this area. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Challenges to synthesis, structural and photophysical characterization of boroles, as well as their rich and often unexpected reactivity can be ascribed to the inherent antiaromatic destabilization of boroles.…”

Section: Introductionmentioning

confidence: 99%

“…This has hitherto been achieved by substitution with aryl or thienyl groups. [1,6,15] The substituent at the boron atom is variable over a broad range from halogen, [4,6,12] amino, [4] and aryl groups [2,5,6,14,15] to transition metals [10,23] and cyclopentadienyl moieties in transition-metal complexes. [3,11,16,17] Variation of the substituent at the boron center significantly affects the HOMO-LUMO transition, thereby resulting in different photophysical properties.…”

Section: Introductionmentioning

confidence: 99%

Lewis Acid–Base Adducts of 1‐Mesityl‐ and 1‐Chloro‐2,3,4,5‐tetraphenylborole

et al. 2013

View full text Add to dashboard Cite

Electron‐deficient borole compounds exhibit a pronounced Lewis acidity that is enhanced due to their antiaromatic character so that even weak donors datively coordinate to form Lewis acid–base adducts. This contribution presents the synthesis and structural characterization of Lewis acid–base adducts formed by the reaction of 1‐mesityl‐2,3,4,5‐tetraphenylborole and 4‐picoline as well as 1‐chloro‐2,3,4,5‐tetraphenylborole with various donors. The new compounds are characterized by means of multinuclear NMR spectroscopy and single‐crystal X‐ray diffraction techniques and compared to related systems.

show abstract

“…In this category, we have chosen the archetypical pentaphenylborole (1) by Eisch [4] as our reference system. As has been previously reported in the literature and as expected from the Hückel 4n+2 rule, [44] this compound is antiaromatic based on the magnetic aromaticity index (NICS(0) = 12.90).…”

Section: Monoborolesmentioning

confidence: 99%

A theoretical study of the aromaticity in neutral and anionic borole compounds

et al. 2015

View full text Add to dashboard Cite

Abstract:In this contribution, we have evaluated the (anti)aromatic character of thirty-four different borole compounds in their neutral and reduced states based on two aromaticity indices, namely nucleus-independent chemical shift (NICS) and multicenter indices (MCI), calculated at the PBE0/6-31+G(d,p) level of theory. Both indices corroborate the notion that neutral borole compounds are antiaromatic and become increasingly aromatic upon addition of electrons. Effects of the ring substituents on the degree of (anti)aromaticity are discussed together with differences in the two theoretical methods, which are on the one hand based on magnetic (NICS) and on the other hand based on electronic criteria (MCI).

show abstract

Synthesis of pentaphenylborole, a potentially antiaromatic system

Abstract: 4) W. H. Pirkle and S. D. Beare, ibid., in press.transformation. The generality of this technique and its application in the determination of absolute configurations will be the subject of a later report.

Cited by 197 publications

References 6 publications

Probing antiaromaticity: resonance Raman investigation of a series of differently substituted boroles

Probing antiaromaticity: resonance Raman investigation of a series of differently substituted boroles

Lewis Acid–Base Adducts of 1‐Mesityl‐ and 1‐Chloro‐2,3,4,5‐tetraphenylborole

A theoretical study of the aromaticity in neutral and anionic borole compounds

Contact Info

Product

Resources

About