Palladium-catalyzed five-fold B–H/C–H cross coupling of monocarboranes with alkenes enables the synthesis of selectively penta-functionalized boron clusters.

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.

The anionic 12-ethynyl-monocarba-closo-dodecaborate cluster is employed as a ligand for the preparation of Cu(i) and heterobimetallic Cu(i)/Pd(ii) or Cu(i)/Pt(ii) complexes.

The lithiacarborane [Li−CB11H11]− plays a central role in carborane chemistry, as it is a key intermediate to achieve the selective functionalization of the monocarba‐closo‐dodecaborate [CB11H12]− for applications in various fields. Also, it is an organometallic species of fundamental interest because it represents a 3D analogue of phenyllithium featuring an exo C−Li bond in addition to the delocalized negative endo charge of the spherical cluster. For the first time, the elusive and highly reactive endo/exo formal dianion [CB11H11]2− has been isolated as its lithiate as well as zincate in pure form and fully characterized. DFT calculations corroborate the experimental findings and underscore the remarkably high reactivity of the lithiacarborane. Subsequent derivatizations demonstrate the relevance of its initial clean formation.

The preparation of the carborane acid chloride [1-(COCl)–CB11H11]− from the carboxylic acid [1-(COOH)–CB11H11]− and subsequent amide formation are reported.