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We report the first crystal structure of heteroleptic Grignard reagent 2based on the carborane endo/exodianion [CB11H11-12-C≡C]2–. Full characterization reveals a rare coordination pattern and affirms the bimetallic nature. Navigating the reactivity landscape, we unlock the potential of 2in nucleophilic addition with ketones to afford propargylic alcohols 3, renowned for their synthetic versatility and potential biological activities, and unveil the Meyer–Schuster rearrangement, yielding α,β-unsaturated carbonyl compounds 4. This narrative of synthesis, characterization, and reactivity opens new horizons for carborane chemistry, offering avenues for innovation and facile functionalization of carborane scaffolds.

Exploration of new organometallic systems based on polyhedral boron clusters has the potential to solve challenging chemical problems such as the stabilization of reactive intermediates and transition-state-like species postulated for E–H (E = H, B, C, Si) bond activation reactions. We report on facile and clean B–H activation of a hydroborane by a new iridium boron cluster complex. The product of this reaction is an unprecedented and fully characterized transition metal-stabilized boron cation or borenium. Moreover, this intermediate bears an unusual intramolecular B···H interaction between the hydrogen originating from the activated hydroborane and the cyclometallated metal-bonded boron atom of the boron cluster. This B···H interaction is proposed to be an arrested insertion of hydrogen into the Bcage–metal bond and the initiation step for iridium “cage-walking” around the upper surface of the boron cluster. The “cage-walking” process is supported by the hydrogen–deuterium exchange observed at the boron cluster, and a mechanism is proposed on the basis of theoretical methods with a special focus on the role of noncovalent interactions. All new compounds were isolated and fully characterized by NMR spectroscopy and elemental analysis. Key compounds were studied by single crystal X-ray diffraction and X-ray photoelectron spectroscopy.

A series of cage penta-arylated carboranes have been synthesized by palladium-catalyzed intermolecular coupling of the C-carboxylic acid of the monocarba-closo-dodecaborate anion [CB11H12]−with iodoarenes by direct cage B–H bond functionalization. These transformations set a record in terms of one-pot directing group-mediated activation of inert bonds in a single molecule. The methodology is characterized by high yields, good functional group tolerance, and complete cage regioselectivity. The directing group COOH can be easily removed during or after the intermolecular coupling reaction. The mechanistic pathways were probed using density functional theory calculations. A Pd(II)–Pd(IV)–Pd(II) catalytic cycle is proposed, in which initial coupling is followed by preferred B–H activation of the adjacent boron vertex, and continuation of this selectivity results in a continuous walking process of the palladium center. The methodology opens a new avenue toward building blocks with 5-fold symmetry.

A convenient method to perdeuterate aromatic compounds is reported. Commercially available nonaflic acid (C4F9SO3H) in combination with C6D6as the deuterium source provided access to a series of highly labeled arenes. Some of them were then used as building blocks for the preparation of functionalized deuterated products. A wide range of synthetic procedures were investigated. They involved traditional methods such as halogenation or nucleophilic substitution, but also metal‐catalyzed cross coupling and C−X bond activation. The transformations comprised redox‐neutral, oxidative as well as reductive reactions, and mechanistically, ionic, radical and pericyclic processes were covered. Under many conditions, the overall degree of deuteration remained high; in C−X activation reactions, a more pronounced re‐protonation was observed. Watch it in H/D: A convenient method to perdeuterate aromatic compounds is reported using catalytic nonaflic acid and C6D6. Many of the deuterated aromatic building blocks can be functionalized under various conditions to afford products with an overall high degree of isotopic labeling.

Si(mply) rips it apart: CF activation of fluorobenzene has been achieved using the extremely strong silyl Lewis acids [Et3Si(X)]+(X=PhF or Et3SiH) and [(2,6‐dixylyl‐C6H3)SiMe2]+paired with the anion CHB11Cl11−. They abstract fluoride from unactivated fluorobenzene to give arylated products, consistent with phenyl‐cation‐like reactivity (see scheme).

Saurer Angriff: Die C‐F‐Aktivierung von Fluorbenzol gelang mit den äußerst starken Silyl‐Lewis‐Säuren [Et3Si(X)]+(X=PhF oder Et3SiH) und [(2,6‐Dixylyl‐C6H3)SiMe2]+im Team mit dem Anion CHB11Cl11−. Sie spalten Fluorid aus nichtaktiviertem Fluorbenzol ab und liefern so arylierte Produkte, entsprechend einer Phenylkation‐artigen Reaktivität (siehe Schema).

Sly silyl caught in the act: Protonation of a mesitylene ring by the strongly acidic arenium carborane CH3C6H6 CHB11Me5Br6 initiates a cascade reaction that results in a stable βsilyl allyl cation see picture, Hyellow, Cblue, silyl allyl groupred. Remarkably, the driving force in the reaction suffices to disrupt a stable aromatic ring in favor of a cationic reactive intermediate.

Die Protonierung eines Mesitylenringsdurch das stark saure Areniumcarboran CH3C6H6CHB11Me5Br6 löst eine Reaktionskaskade aus, die zu einem stabilen βSilylallylkation führt siehe Bild, Hgelb, Cblau, Silylallylgrupperot. Dass die Triebkraft der Reaktion ausreicht, um einen stabilen aromatischen Ring zugunsten einer kationischen reaktiven Zwischenstufe zu zerstören, ist bemerkenswert.

The identification of an alternative chemical space in order to address the global challenge posed by emerging antimicrobial resistance is very much needed for the discovery of novel antimicrobial lead compounds. Boron clusters are currently being explored in drug discovery due to their unique steric and electronic properties. However, the challenges associated with the synthesis and derivatization techniques of these compounds have limited their utility in the rapid construction of a library of molecules for screening against various biological targets as an alternative molecular platform. Herein, we report a transition-metal-catalyzed regioselective direct B–H alkylation–annulation of the closo-dodecaborate anion with natural products such as menthol and camphor as the directing groups. This method allowed the rapid construction of a library of 1,2,3-trisubstituted clusters, which were evaluated in terms of their antibacterial activity against WHO priority pathogens. Several of the synthesized dodecaborate derivatives displayed medium- to high-level bactericidal activity against Gram-positive and Gram-negative bacteria.

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Phenyl cation equivalents, generated from otherwise unreactive aryl fluorides, allow extension of the Friedel—Crafts reaction to intramolecular aryl couplings.