Redox- and Charge-State Dependent Trends in 5, 6, and 7-Membered Boron Heterocycles: A Neutral Ligand Coordination Chemistry Approach to Boracyclic Cations, Anions, and Radicals

Accounts of Chemical Research, Год журнала: 2024, Номер 57(10), С. 1510 - 1522

Опубликована: Май 6, 2024

ConspectusBoron heterocycles represent an important subset of heteroatom-incorporated rings, attracting attention from organic, inorganic, and materials chemists. The empty pz orbital at the boron center makes them stand out as quintessential Lewis acidic molecules, also serving a means to modulate electronic structure photophysical properties in facile manner. As boracycles are ripe for extensive functionalization, they used catalysis, chemical biology, science, continue be explored synthons conjugated reagents. Neutral boron(III)-incorporated polycyclic molecules some most studied types boracycles, understanding their redox transformations is applications relying on electron transfer charge transport. While relevant species can often electrochemically observed, it remains challenging isolate characterize where and/or skeleton have been chemically reduced.We describe our recent work isolating 5-, 6-, 7-membered boracyclic radicals, anions, cations, focusing stabilization strategies, ligand-mediated bonding situations, reactivity. We present versatile neutral ligand coordination chemistry approach that permits transformation potent electrophiles powerful nucleophilic facilitate diverse bond activation chemistry. Although there wide range suitable stabilizing ligands, we employed both diamino-N-heterocyclic carbenes (NHCs) cyclic(alkyl)(amino) (CAACs), which led with tunable structures aromaticity trends. highlight successful isolation borafluorene radicals demonstrate reversible behavior, undergoing oxidation cation or reduction anion. anion synthon has prepare boryl main-group transition-metal bonds, luminescent oxabora-spirocycles, borafluorenate-crown ethers, CO-releasing via carbon dioxide activation. expanded 6-membered characterized bis(NHC-supported 9-boraphenanthrene)s corresponding bis(CAAC-stabilized 9-boraphenanthrene) biradical. detail interconvertible multiredox states boraphenalene, boraphenalenyl radical, anion, mimic charge-states all-hydrocarbon analogue. Reactivity studies displayed unusual reactivity multiple sites periphery tricyclic scaffold. Reduced borepins, containing heterocycles, isolated. stepwise one-pot synthesis combining halo-borepin precursor, CAAC, KC8 afford monomeric borepin anions. π-system was extended contain two rings fused pentacyclic scaffold, permitted diborepin biradicals dibora-quinone core.Our goal provide guide explaining current structure–function trends strategies redox-active boron-incorporated initiate rational design use these compounds across vast space.

Язык: Английский

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Dicationic Boron Derivatives of Schlenk’s and Thiele’s Hydrocarbon

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Март 19, 2025

In recent years, neutral NHC-stabilized boryl radicals have been investigated as reactive species in various organic transformations. However, cationic boron significantly less explored. addition, boron-centered open-shell with S > 1/2 emerged attractive synthetic targets. this study, we provide a route to an radical cation salt of the weakly coordinating [Al(ORF)4]- (RF = C(CF3)3) anion. The procedure was extended dicationic diboron derivatives Schlenk's and Thiele's hydrocarbons meta- para-phenylene coupling units between spin centers. While most known isolable biradicals singlet ground-state thermally accessible triplet state, version hydrocarbon occupies spin-state, shown by combined electron paramagnetic resonance spectroscopy density functional theory studies. Furthermore, initial reactivity studies dications elemental sulfur diphenyldiselenide are presented.

Язык: Английский

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Diboron-Incorporated Indenofluorene: Isolation of Crystalline Neutral and Reduced States of 6,12-Diboraindeno[1,2-b]fluorene

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Май 21, 2025

The synthesis and redox transformations of 6,12-diboraindeno[1,2-b]fluorene (DBIF)─a pentacyclic π-system with diboron incorporation─are reported. In notable contrast to the all-hydrocarbon indenofluorenes, a ligand coordination reduction strategy allows tuning electronic structure across four states. Accordingly, we introduce an 18π e- neutral DBIF, 20π diradical, 21π radical anion, 22π dianion, all which have been isolated structurally authenticated. diradicals exhibit diradical character up 77% possess open-shell singlet ground states thermally accessible triplet

Язык: Английский

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Functions Containing at Least One Group 15 Element (and No Halogen or Chalcogen)

Elsevier eBooks, Год журнала: 2025, Номер unknown

Опубликована: Янв. 1, 2025

Язык: Английский

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Planarity Is Not Plain: Closed- vs Open-Shell Reactivity of a Structurally Constrained, Doubly Reduced Arylborane toward Fluorobenzenes

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Май 29, 2025

The ability to activate small molecules is imparted 9,10-dihydro-9,10-diboraanthracenes (DBAs) through the injection of two electrons. We report on activation fluorobenzenes C6FnH6-n by doubly reduced, structurally constrained DBA [1]2- in THF (n: 1,3,4,5,6). Compound 1 a 9,10-diphenyl DBA, forced into planarity methylene bridges between phenyl substituents and core. This rigidity results enhanced stability under ambient conditions an elevated planar-to-pyramidal reorganization energy upon boron tetracoordination, unlocking new reactivity. dianion salts M2[1] were synthesized excellent yields stirring neutral with alkali metals M (M: Li, Na, K); comproportionation Li2[1] generates blue radical salt Li[1], characterized EPR spectroscopy X-ray diffraction. While inert toward C6FH5 up 120 °C, it reacts 1,3,5-C6F3H3 at 100 °C yield B(sp2)/B(sp3) adduct difluorophenyl ligand (Li[2]). Treatment eq. C6F5H or C6F6 induces selective monohydrodefluorination, occurring parallel formation unique tetrahydrofuran-2-yl (Li[3]). three isomers C6F4H2 represent intermediate cases, where competition trifluorophenyl- tetrahydrofuran-2-yl-adduct governed relative positions F nature countercation (M+: Li+, K+). Through experimental quantum-chemical studies, we unveil underlying reaction mechanisms show that acts either as B-centered nucleophile SNAr-type conversion (low benzene fluorination) reducing agent single-electron transfer/H atom abstraction sequence (high fluorination).

Язык: Английский

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Crystalline Boron‐Centered Analogues of Müller's Hydrocarbon

Chinese Journal of Chemistry, Год журнала: 2024, Номер unknown

Опубликована: Июнь 16, 2024

Comprehensive Summary Müller's hydrocarbon is a well‐known open‐shell singlet diradicaloid, yet its structural determination and redox property remain elusive due to extremely high reactivity. Herein, we report the successful synthesis full characterizations of first neutral boron‐centered analogue ( 4 ) hydrocarbon, along with dianionic 5 2− featuring three isolable states. In presence two equivalents N‐heterocyclic carbene (NHC), reduction 4,4”‐bis(triisopropylphenylbromoboryl)terphenyl 3 potassium graphite afforded NHC‐stabilized boryl diradicaloid near‐pure diradical character y 0 = 0.93). Stepwise reductions 4,4”‐bis(dimesitylboryl)terphenyl in THF yielded monoradical anion ·− dianion , respectively, accompanied by decreasing aromaticity within conjugated spacer. Experimental studies theoretical analyses revealed that both exhibit large spin distributions at boron atoms, ground states, small singlet‐triplet energy gaps.

Язык: Английский

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Crystalline Radical Anion of a Diboratriazole and Its Conversion to a Neutral Radical Driven by a Carbene

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(30), С. 20945 - 20950

Опубликована: Июль 21, 2024

One-electron reduction of diboratriazole

Язык: Английский

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Pentacyclic fused diborepinium ions with carbene- and carbone-mediated deep-blue to red emission

Chemical Science, Год журнала: 2024, Номер 15(35), С. 14358 - 14370

Опубликована: Янв. 1, 2024

Designing molecules that can undergo late-stage modifications resulting in specific optical properties is useful for developing structure-function trends materials, which ultimately advance optoelectronic applications. Herein, we report a series of fused diborepinium ions stabilized by carbene and carbone ligands (diamino-N-heterocyclic carbenes, cyclic(alkyl)(amino) carbodicarbenes, carbodiphosphoranes), including detailed bonding analysis. These are the first structurally confirmed examples diborepin dications detail how distortions core pentacyclic system impact aromaticity, stability, their light-emitting properties. Using same scaffold, coordinating were used to dramatically shift emission profile, exhibit colors ranging from blue red (358-643 nm). Notably, these access expanded regions visible spectrum compared known borepins, with quantum yields up 60%. Carbones determined be superior stabilizing ligands, improved stability solution solid states. Density functional theory was provide insight into as well transitions result observed photophysical

Язык: Английский

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Ligand-Tuned Open- and Closed-Shell Diborepins

Synfacts, Год журнала: 2024, Номер 20(07), С. 0692 - 0692

Опубликована: Июнь 14, 2024

Key words diborepins - open-shell singlet bora-quinone biradical

Язык: Английский

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