Successive carbene insertion into 9-phenyl-9-borafluorene

Bartholome, Tyler A.; Bluer, Kristen R.; Martin, Caleb D.

doi:10.1039/c9dt01032g

Cited by 24 publications

(22 citation statements)

References 69 publications

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“…Interestingly, insertion of nitrogen atom (bonded to boron) into the B─C bond of borole could lead to highly exothermic product 1S.P2. The Insertion of N atoms from azides, diazoalkanes, and isocyanides into borole rings leading to ring expansion has been demonstarted extensively by the groups of Braunschweig and Martin . Exothermicity of this second step should be linked to the formation of aromatic BN‐doped benzene from antiaromatic borole.…”

Section: Resultsmentioning

confidence: 99%

“…The Insertion of N atoms from azides, diazoalkanes, and isocyanides into borole rings leading to ring expansion has been demonstarted extensively by the groups of Braunschweig and Martin. [42][43][44][45][46] Exothermicity of this second step should be linked to the formation of aromatic BN-doped benzene from antiaromatic borole. Due to the best performance for N 2 activation (discussed earlier in this study), Borole-1SiH 3 -2345-CF 3 , and NHC6 were chosen to create unprecedented NHC-borole FLPs for testing N 2 activation (Figure 4a).…”

Section: Designing Flps Based On Nhc and Boron Moietiesmentioning

confidence: 99%

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Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

Rouf

Dai

et al. 2020

Advcd Theory and Sims

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Molecular nitrogen (N2), an abundant component of the atmosphere, is appealing for industrial value‐added products. However, its intrinsic inertness limits its activation to mainly metallic species. Environmental concerns and harsh reaction conditions have resulted in a demand for alternate nonmetallic and nontoxic routes to activate and functionalize N2 at ambient conditions. Comprehensive density functional theory (DFT) calculations are performed on N2 activation by boron species, specifically for the experimentally more accessible tricoordinated boron compounds. Subsequently designed frustrated Lewis pairs (FLPs) combining screened N‐heterocyclic carbene with boron moieties can make N2 activation both kinetically and thermodynamically favorable, displaying high potential for metal‐free N2 activation. The significant thermodynamic stability of the products stabilized by aromaticity and low activation barriers could be a breakthrough for the development of FLP chemistry on metal‐free N2 activation.

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Section: Resultsmentioning

confidence: 99%

Section: Designing Flps Based On Nhc and Boron Moietiesmentioning

confidence: 99%

Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

Rouf

Dai

et al. 2020

Advcd Theory and Sims

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“…This also results in a lower Lewis acidity and, subsequently, significantly more stable systems . Detailed studies by Martin and co‐workers demonstrate, however, that sterically less hindered derivatives, in particular, retain characteristic borole reactivity . Compared with their triarylborane derivatives, borafluorenes are usually more Lewis acidic and exhibit more positive reduction potentials .…”

Section: Introductionmentioning

confidence: 99%

Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9‐Borafluorenes

Rauch

Fuchs

Friedrich

et al. 2020

Chemistry A European J

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Three differentp erfluoroalkylated borafluorenes (F Bf)w ere prepared and their electronic and photophysical properties were investigated. The systemsh ave four trifluoromethyl moieties on the borafluorene moiety as well as two trifluoromethyl groups at the ortho positions of their exo-aryl moieties. They differ with regard to the para substituents on their exo-aryl moieties, being ap roton(F Xyl F Bf, F Xyl:2 ,6-bis(trifluoromethyl)phenyl), at rifluoromethyl group (F Mes F Bf, F Mes:2 ,4,6-tris(trifluoromethyl)phenyl) or ad imethylamino group (p-NMe 2-F Xyl F Bf, p-NMe 2-F Xyl:4-(dimethylamino)-2,6-bis(trifluoromethyl)phenyl), respectively.A ll derivatives exhibit extraordinarily low reduction potentials, comparable to those of perylenediimides. The most electron-deficient derivative F Mes F Bf wasa lso chemically reduced and its radicala nion isolated and characterized. Furthermore, all compounds exhibit very long fluorescent lifetimes of about 250 ns up to 1.6 ms; however, the underlying mechanismsresponsible for this differ.T he donor-substitutedd erivative p-NMe 2-F Xyl F Bf exhibitst hermally activated delayedf luorescence (TADF) from ac harge-transfer (CT) state, whereas the F Mes F Bf and F Xyl F Bf borafluorenese xhibit only weakly allowed locally excited (LE) transitions due to their symmetry and low transition-dipole moments.

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“…[3] The neutral tricoordinate borafluorene (Figure 1 a) has been explored extensively and shows interesting reactivity with alkynes, [2b, 4] azides, [2c, 5] 1,2-dipolar substrates, [6] and carbenes. [7] In addition, bora-fluorene-based polymers exhibit high luminescence quantum yields. [2f] While the structure of the first borafluorene cation (i.e., borafluorenium) was reported by Nçth over three decades ago, [1b] we recently described the synthesis, optical tuning, and thermochromism of borafluorenium species supported by carbenes (Figure 1 b).…”

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confidence: 99%

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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Successive carbene insertion into 9-phenyl-9-borafluorene

Abstract: The reactions of 9-phenyl-9-borafluorene with trimethylsilyldiazomethane in a 1 : 1 and 1 : 2 stoichiometry furnished the corresponding BC5 and BC6 heterocycles via the formal insertion of one and two carbene units.

Cited by 24 publications

References 69 publications

Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

Dinitrogen Activation by Tricoordinated Boron Species: A Systematic Design

Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9‐Borafluorenes

Persistent Borafluorene Radicals

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