9‐Borafluorenes

Köster, Roland; Benedikt, G.

doi:10.1002/anie.196303232

Cited by 37 publications

(35 citation statements)

References 5 publications

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“…For example, 2-biphenyldiphenyl borane evolves benzene and forms 9-phenylborafluorene, 14, only at temperatures 4280 1C. Whereas Köster and co-workers 24 found that the formation of 9-borafluorenes via electrophilic borylation using B-H containing intermediates and evolving H 2 proceeded at 120 1C. In most cases the major factor controlling reaction temperature in these studies is accessing the R 2 BH/RBH 2 electrophile that effects C-H borylation.…”

Section: Intramolecular Electrophilic C-h Borylation: the Early Yearsmentioning

confidence: 95%

Intramolecular (directed) electrophilic C–H borylation

et al. 2020

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Section: Intramolecular Electrophilic C-h Borylation: the Early Yearsmentioning

confidence: 95%

Intramolecular (directed) electrophilic C–H borylation

et al. 2020

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“…Figure 5. Shapes of the deformation densities D1 (1) and D1 (2) , which are associated with the orbital interactions DE orb (1) and DE orb(2) in 2 NMe and 4 NMe , and eigenvalues j n n j of the charge flow. The isosurface value is 0.001.…”

Section: Zuschriftenmentioning

confidence: 99%

“…The dispersion is only responsible for 3-4 % of the total attraction. The breakdown of DE orb into pairwise orbital interactions shows that the strongest orbital interaction, DE orb (1) , originates from the [L]! [borafluorene] s-donation (67-72 % of total DE orb ), whereas the next important orbital term, DE orb(2) , is due to the [L] !…”

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confidence: 99%

“…The associated charge flow (red!blue) is nicely reflected in the corresponding plots of deformation densities (D1) along with the charge eigenvalues in Figure 5. The stronger s-donating and p-accepting ability of the CAAC compared to the NHC is clearly understood from the relative size of DE orb (1) and DE orb(2) , and from the corresponding charge eigenvalues, j n j . To gain insight into the redox properties of 2 and 4, cyclic voltammograms (CV) were recorded in THF ( Figure 6).…”

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confidence: 99%

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Persistent Borafluorene Radicals

et al. 2020

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N‐Heterocyclic carbene (NHC)‐ and cyclic (alkyl)(amino)carbene (CAAC)‐stabilized borafluorene radicals have been isolated and characterized by elemental analysis, single‐crystal X‐ray diffraction, UV/Vis absorption, cyclic voltammetry (CV), electron paramagnetic resonance (EPR) spectroscopy, and theoretical studies. Both the CAAC–borafluorene radical (2) and the NHC–borafluorene radical (4) have a considerable amount of spin density localized on the boron atoms (0.322 for 2 and 0.369 for 4). In compound 2, the unpaired electron is also partly delocalized over the CAAC ligand carbeneC and N atoms. However, the unpaired electron in compound 4 mainly resides throughout the borafluorene π‐system, with significantly less delocalization over the NHC ligand. These results highlight the Lewis base dependent electrostructural tuning of materials‐relevant radicals. Notably, this is the first report of crystalline borafluorene radicals, and these species exhibit remarkable solid‐state and solution stability.

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“…[42,43] However,t he diversity in substitution patternsa tt he butadiene backbone is lessd eveloped. Apart from benzannelated boroles (9-borafluorenes and boraindenes), [55][56][57][58][59][60][61] which are known to reveal different electronic properties, only af ew derivatives of stable free boroles with ab ackboneo ther than a tetraphenylbutadiene are documentedi nt he literature (Scheme 1). Yamaguchi reported on electron-rich thienyl groups in the butadieneb ackbone, whichl ed to markedly altered HOMO-LUMO gaps.…”

Section: Introductionmentioning

confidence: 99%

Electronic Push–Pull Modulation by Peripheral Substituents in Pentaaryl Boroles

Heitkemper

Sindlinger

2019

Chemistry A European J

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Establishing access to a bulky tetraaryl dilithiobutadiene (Ph*C)4Li2 (Ph*=3,5‐tBu2(C6H3)) allowed for the synthesis of five‐membered heterocycles with incorporated main‐group elements. Along with an amino borole, a set of substituted pentaaryl boroles (Ph*C)4BAr has been synthesized. The examination of their absorption spectra and computational studies by means of DFT granted insight into the influence of peripheral substituents on the electronic features of the parent pentaphenyl borole (PhC)4BPh. Introduction of the more electron‐rich Ph* residue at the carbon atoms increases the HOMO energy, redshifting the visible π/π*‐absorption bands compared with the parent pentaphenyl borole. The influence on the frontier orbitals of three different boron‐bound aryls with electronically modulating substituents in the remote 3,5‐positions Ar=3,5‐R2‐C6H3 (R=Me, H, CF3) was studied. The substituents were found to increase (+I effect, Me) or decrease (−I effect, CF3) the LUMO energy, thus directly affecting the visible absorption spectra. This represents the first study on HOMO–LUMO‐gap adjustments by a combined push–pull approach of a substituted pentaphenylborole.

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9‐Borafluorenes

Cited by 37 publications

References 5 publications

Intramolecular (directed) electrophilic C–H borylation

Intramolecular (directed) electrophilic C–H borylation

Persistent Borafluorene Radicals

Electronic Push–Pull Modulation by Peripheral Substituents in Pentaaryl Boroles

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