Classically closo-carborane anions, particularly
[HCB11H11]− and [HCB9H9]−, and their derivatives have primarily
been used as weakly coordinating anions to isolate reactive intermediates,
platforms for stoichiometric and catalytic functionalization, counteranions
for simple Lewis acid catalysis, and components of materials like
liquid crystals. The aim of this article is to educate the reader
on the contemporary nonclassical applications of these anions. Specifically,
this review will cover new directions in main group catalysis utilized
to achieve some of the most challenging catalytic reactions such as
C–F, C–H, and C–C functionalizations that are
difficult or impossible to realize with transition metals. In addition,
the review will cover the utilization of the clusters as dianionic
C σ-bound ligands for coordination chemistry, ligand substituents
for coordination chemistry and advanced catalyst design, and covalently
bound spectator substituents to stabilize radicals. Furthermore, their
applications as solution-based and solid-state electrolytes for Li,
Na, and Mg batteries will be discussed.
Solid-state
ion conductors based on closo-polyborate
anions combine high ionic conductivity with a rich array of tunable
properties. Cation mobility in these systems is intimately related
to the strength of the interaction with the neighboring anionic network
and the energy for reorganizing the coordination polyhedra. Here,
we explore such factors in solid electrolytes with two anions of the
weakest coordinating ability, [HCB11H5Cl6]− and [HCB11H5Br6]−, and a total of 11 polymorphs are identified
for their lithium and sodium salts. Our approach combines ab initio
molecular dynamics, synchrotron X-ray powder diffraction, differential
scanning calorimetry, and AC impedance measurements to investigate
their structures, phase-transition behavior, anion orientational mobilities,
and ionic conductivities. We find that M(HCB11H5X6) (M = Li, Na, X = Cl, Br) compounds exhibit order–disorder
polymorphic transitions between 203 and 305 °C and display Li
and Na superionic conductivity in the disordered state. Through detailed
analysis, we illustrate how cation disordering in these compounds
originates from a competitive interplay among the lattice symmetry,
the anion reorientational mobility, the geometric and electronic asymmetry
of the anion, and the polarizability of the halogen atoms. These factors
are compared to other closo-polyborate-based ion
conductors to suggest guidelines for optimizing the cation–anion
interaction for fast ion mobility. This study expands the known solid-state
poly(carba)borate-based materials capable of liquid-like ionic conductivities,
unravels the mechanisms responsible for fast ion transport, and provides
insights into the development of practical superionic solid electrolytes.
In this first
reaction, the authors express their opinion about the misgivings of
CHN combustion analysis. These views are in reaction to the manuscript
titled An International
Study Evaluating Elemental Analysis.
C-H functionalization of undecahalogenated carborane anions, [HCB11X11-] (X = Cl, Br, I), is performed with Cs2CO3 in acetonitrile. We show that the requisite Cl, Br and I carborane dianions can...
Correction for ‘Cesium carbonate mediated C–H functionalization of perhalogenated 12-vertex carborane anions’ by Sergio O. Lovera et al., Chem. Commun., 2022, 58, 4060–4062, DOI: https://doi.org/10.1039/D2CC00173J.
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