Carbaboranes as Pharmacophores: Properties, Synthesis, and Application Strategies

An innovative type of lithium decahydroborate (Li@B10H14) complex with a basketlike complexant of decaborane (B10H14) has been designed using quantum mechanical methods. As Li atom binds in a handle fashion to terminal electrophilic boron atoms of the decaborane basket, its NBO charge q (Li) is found to be 0.876, close to +1. This shows that the Li atom has been ionized to form a cation and an anion at the open end of B10H14. The most fascinating feature of this Li doping is its loosely bound valence electron, which has been pulled into the cavity of the B10H14 basket and become diffuse by the electron-deficient morphological features of the open end of the B10H14 basket. Strikingly, the first hyperpolarizability (β0) of Li@B10H14 is about 340 times larger than that of B10H14, computed to be 23 075 au (199 × 10−30 esu) and 68 au, respectively. Besides this, the intercalation of the Li atom to the B10H14 basket brings some distinctive changes in its Raman, 11B NMR, and UV−vis spectra along with its other e...

Quantum Mechanical Design and Structure of the Li@B10H14 Basket with a Remarkably Enhanced Electro-Optical Response

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 a...

Nonclassical Applications of closo-Carborane Anions: From Main Group Chemistry and Catalysis to Energy Storage

Carboranes, a class of carbon-boron molecular clusters, are often viewed as three-dimensional analogues of benzene. They are finding increasing applications as useful functional building blocks in materials science, medicine, organometallic/coordination chemistry and more. Thus, functionalization of carboranes has received considerable attention. In comparison with the weakly acidic cage C-H bonds that can be readily functionalized, selective cage B-H functionalization among ten chemically similar BH vertices in o-carboranes is very challenging. Only in the recent few years, considerable progress has been made in transition metal catalyzed vertex-specific BH functionalization. This review summarizes recent advances in this research area.

Controlled functionalization of o-carborane via transition metal catalyzed B–H activation

Molecular motion of two nearly icosahedral molecules, ortho‐ and meta‐carborane, in the solid state has been studied by x‐ray diffraction, calorimetric, and NMR techniques. At 25°C the powder diffraction patterns for both crystals are consistent with a fcc unit cell of dimension 9.86 A containing four molecules. For both isomers the corresponding molecular site symmetry is higher than the molecular symmetry, implying molecular orientational disorder at this temperature. That the orientational disorder is of a kinetic nature is confirmed by NMR measurements. The proton resonance line second moment at 25°C is 0.711 ± 0.051 G2 for o‐carborane and 0.82 ± 0.10 G2 for m‐carborane. This can be compared with a line second moment of 0.630 G2 calculated assuming rapid isotropic molecular reorientation and a line second moment of 34 G2 calculated for the rigid lattice. For both isomers the observed second moment is much smaller than calculated assuming rotation about the molecular twofold axis, implying rapid reorie...

NMR, Calorimetric, and Diffraction Study of Molecular Motion in Crystalline Carboranes

The structure of B10C2H12(barene) and its derivatives

CONTENTS I. Introduction?424 II. Structure and reactivity of decaborane?425 III. Deuterium exchange in decaborane?427 IV. Pyrolysis of decaborane?428 V. Hydrolysis, alcoholysis, and thiolysis?428 VI. Decaborane as an acid?429 VII. Decaborane Grignard reagents and sodium tridecahydrodecaborate(1-)?429 VIII. Nucleophilic substitution in decaborane?430 IX. Electrophilic substitutions?432 X. The stable anion B10H102-?432 XI. Carboranes?434

https://iopscience.iop.org/article/10.1070/RC1965v034n06ABEH001455/pdf

The chemistry of decaborane and its derivatives

Synthesis of a new class of organoboron compounds, B10C2H12(barene) and its derivatives

Metallation of B10C2H12(barene) and its derivatives by butyl lithium

1.

The molecules of o-carboranes-12 form in the gas phase long-lived negative molecular ions by the resonance capture of electrons with thermal and epithermal energies; their main decomposition channel is autocleavage of an electron.




2.

Isomerization of the carborane skeleton to the o-isomer occurs not only in the case of the dianions in solution, but also in the step of forming the anion-radical.

V. I. Stanko

Papers

The structure of B10C2H12(barene) and its derivatives

The chemistry of decaborane and its derivatives

Synthesis of a new class of organoboron compounds, B10C2H12(barene) and its derivatives

Metallation of B10C2H12(barene) and its derivatives by butyl lithium

Study of anion-radicals of carboranes-12 in the gas phase by the mass spectrometry method of the resonance capture of electrons