Cationic -Tricarbollide μ-10,11-H-10,11-H-7-MeN--7,8,9-CBH and Its Halogenated Derivatives: The Slow Iodination Process Occurring through Cationic Iodonium Tricarbollides.

A series of -tricarbollides based on 10,11-X-7-MeN--7,8,9-CBH (X = H, Cl, Br, I) and their protonated, i.e. cationic, counterparts, which have an extra H-bridge over the B10-B11 vector in the open pentagonal belt, were prepared.

Modification of cobalt bis(dicarbollide) ions with nitrile groups on carbon atoms: a unique low-temperature skeletal rearrangement due to the specific electron-donor character of CN substitution.

Herein, we report on the synthesis and stereochemistry of mono- and isomeric dinitrile derivatives of [(1,2-CBH)-3,3'-Co] ions. The shape and electronic properties of CN groups can apparently surmount the strain associated with the substitution of two vicinal carbon positions. Owing to electron donation to the cage, this results in a substituent-induced rearrangement of one of the carbon atoms to the upper pentagonal ring.

Heats of formation on the way from BH to BH: thermochemical consequences of multicenter bonding in and DFT methods.

The objective of this study is to evaluate the effectiveness of various computational methods in reproducing the experimental heats of formation of boron hydrides using the atomization energy approach. The results have demonstrated that the empirical dispersion combined with the BJ damping function provided too large intramolecular dispersion energies, thereby compromising the accuracy of the outcomes produced by the DFT-D3 methods. Additionally, the CCSD(T) method has reproduced the experimental values only when combined with a basis set optimized for an accurate description of the core-valence correlation effect.

Preparation, Structure, Reactivity, Lewis Acidic and Fluorescence Properties of Arylpyridine Based Boron C,N-Chelates Featuring Weakly Coordinating Anions.

Herein, we present the preparation of a series of electronically and/or sterically distinct borenium-type species based on a simple 2-arylpyridine scaffold. Corresponding arylpyridine was firstly subjected to electrophilic borylation (BBr/i-PrNEt) and formed BBr chelate was reduced with LiAlH to yield arylpyridine boron dihydride. Elimination of one hydride led to Lewis acidic borenium-like products.

A Direct Route to closo-SBCl Thiaboranes from Simple Electron-Precise Synthons: The Different Role of Chalcogen Bonding in SBCl and SBCl Crystals.

Six-vertex closo-SBCl (1) and ten-vertex closo-1-SBCl (2) thiaboranes have been prepared, besides the already known 12-vertex closo-SBCl (3), from the co-pyrolysis reaction of BCl with SCl at 280 °C in vacuo. The compounds are sublimable, off-white solids. Their elemental composition has been determined by high-resolution mass spectrometry.

Chlorinated polyhedral selenaboranes revisited by joint experimental/computational efforts: the formation of -1-SeBCl and the crystal structure of -SeBCl.

The recent success in the formation of chlorinated telluraboranes and the reactivities of pnictogenaboranes prompted us to re-examine the vacuum co-pyrolysis of BCl with SeCl at various molar ratios and temperatures in order to search for the generation of other polyhedral selenaboranes than -SeBCl (1a) and -SeBCl (1b), the latter being observed earlier. Interestingly, a new compound with the elemental composition SeBCl (2) was detected, this time by high- and low-resolution mass spectrometry. Further characterization by 1- and 2-D B-NMR spectroscopy suggests that 2 should adopt a closed bicapped square-antiprismatic geometry with selenium at the apical position.

Boron-based octahedral dication experimentally detected: DFT surface confirms its availability.

Borane and heteroborane clusters have been known as neutral or anionic species. In contrast to them, several ten-vertex monocationic and dicarbaborane-based systems have recently emerged from the reaction of the parent bicapped-square antiprismatic dicarbaboranes with N-heterocyclic carbenes followed by the protonization of the corresponding intermediates. The expansion of these efforts has afforded the very first -dicationic octahedral phosphahexaborane along with new monocationic pnictogenahexaboranes of the same shapes.

DFT Surface Infers Ten-Vertex Cationic Carboranes from the Corresponding Neutral Ten-Vertex Family: The Computed Background Confirming Their Experimental Availability.

Modern computational protocols based on the density functional theory (DFT) infer that polyhedral ten-vertex carboranes are key starting stationary states in obtaining ten-vertex cationic carboranes. The rearrangement of the bicapped square polyhedra into decaborane-like shapes with open hexagons in boat conformations is caused by attacks of N-heterocyclic carbenes (NHCs) on the motifs. Single-point computations on the stationary points found during computational examinations of the reaction pathways have clearly shown that taking the "experimental" NHCs into account requires the use of dispersion correction.

Two Shared Icosahedral Metallacarboranes through Iron: A Joint Experimental and Theoretical Refinement of Mössbauer Spectrum in [Fe(1,2-CBH)]Cs.

Mössbauer and X-ray photoelectron spectroscopies (XPS) are complemented with high-level quantum-chemical computations in the study of the geometric and electronic structure of the paramagnetic salt of the metallacarborane sandwich complex [Fe(1,2-CBH)]Cs = FeSanCs. Experimental Fe isomer shifts and quadrupole splitting parameters are compared with the theoretical prediction, with good agreement. The appearance of two sets of Cs(3d) doublets in the XPS spectrum, separated by 2 eV, indicates that Cs has two different chemical environments due to ease of the Cs cation moving around the sandwich complex with low-energy barriers, as confirmed by quantum-chemical computations.

The Telluraboranes closo-TeB Cl and closo-TeB Cl with Exceptionally Long Body Diagonals: Synthetic and Bonding Motifs for Innovative Octahedral and Icosahedral Geometries.

Six-vertex closo-TeB Cl (1) and twelve-vertex closo-TeB Cl (2) telluraboranes have been prepared via co-pyrolysis of B Cl with TeCl in vacuo at temperatures between 360 °C and 400 °C. Both compounds are sublimable, off-white solids, and they have been characterized by one- and two-dimensional B NMR and high-resolution mass spectroscopy. Both ab initio/GIAO/NMR and DFT/ZORA/NMR computations support octahedral and icosahedral geometries for 1 and 2, respectively, as expected due to their closo-electron counts.

B-H⋯π and C-H⋯π interactions in protein-ligand complexes: carbonic anhydrase II inhibition by carborane sulfonamides.

Among non-covalent interactions, B-H⋯π and C-H⋯π hydrogen bonding is rather weak and less studied. Nevertheless, since both can affect the energetics of protein-ligand binding, their understanding is an important prerequisite for reliable predictions of affinities. Through a combination of high-resolution X-ray crystallography and quantum-chemical calculations on carbonic anhydrase II/carborane-based inhibitor systems, this paper provides the first example of B-H⋯π hydrogen bonding in a protein-ligand complex.

Reactivity of Perhalogenated Octahedral Phospha- and Arsaboranes toward THF: A Joint Experimental/Computational Study.

Reactions of the perhalogenated polyhedral pnictogenaboranes -1,2-PnBHal (Pn = P, As; Hal = Cl, Br) with Lewis bases are presently being studied with a focus on rationalizing the sites of nucleophilic attacks on clusters bearing σ-holes. These σ-holes are localized both on pnictogens and, for Hal = Br, on bromine atoms, as revealed by electrostatic potential (ESP) and intrinsic bond orbital (IBO) analyses. Surprisingly, the attack of the cyclic ether THF on -1,2-PnBBr does not occur on the site with the largest positive partial charge, centered in the middle of the pnictogen-pnictogen vector.

Rearrangement of dicarboranyl methyl cation to icosahedral C B H : An ab initio dynamics view.

Closo-carborane anions are prominent, whereas the cations of the same are less abundant in the literature. As these ions have similar size and are weakly coordinating, the ionic liquids of these two ions could have important applications in many areas of chemistry. In view of limited number of polyhedral carborane cations available, we revisited the rearrangement of dicarboranyl methyl cation (7-CH 7,9-nido-C B H ) using ab initio molecular dynamics calculations with metadynamics.

Access to cationic polyhedral carboranes via dynamic cage surgery with N-heterocyclic carbenes.

Polyhedral boranes and heteroboranes appear almost exclusively as neutral or anionic species, while the cationic ones are protonated at exoskeletal heteroatoms or they are instable. Here we report the reactivity of 10-vertex closo-dicarbadecaboranes with one or two equivalents of N-heterocyclic carbene to 10-vertex nido mono- and/or bis-carbene adducts, respectively. These complexes easily undergo a reaction with HCl to give cages of stable and water soluble 10-vertex nido-type cations with protonation in the form of a BHB bridge or 10-vertex closo-type cations containing one carbene ligand when originating from closo-1,10-dicarbadecaborane.

Thiaborane Icosahedral Barrier Increased by the Functionalization of all Terminal Hydrogens in -1-SBH.

The electrophilic substitution of icosahedral 1-SBH with methyl iodide has resulted in two B-functionalized thiaboranes, 7,12-I-2,3,4,5,6,8,9,10,11-(CH)-1--SB and 7,8,12-I-2,3,4,5,6,9,10,11-(CH)--1-SB, with the former being significantly predominant. These two icosahedral thiaboranes are the first cases of polysubstituted polyhedral boron clusters with another vertex that differs from B and C. Such polyfunctionalizations have increased the earlier observed thiaborane icosahedral barrier, not exhibiting any reactivity toward bases, unlike the parent thiaborane.

Transformation of various multicenter bondings within bicapped-square antiprismatic motifs: -rearrangement.

Reported herein are mutual rearrangements in the whole series of seven bicapped-square antiprismatic -CBH by means of high-quality computations that disprove the earlier postulated (diamond-square-diamond) scheme for these isomerizations. The experimentally existing -1,2-CBH was able to be converted to 1,6-, and 1,10-isomers by pyrolysis, and the (diamond-square-diamond) mechanism was offered as an explanation of these processes. However, these computations disprove the postulated scheme for these isomerizations that take place in the ten-vertex series.

Benchmark Data Sets of Boron Cluster Dihydrogen Bonding for the Validation of Approximate Computational Methods.

The success of approximate computational methods, such as molecular mechanics, or dispersion-corrected density functional theory, in the description of non-covalent interactions relies on accurate parameterizations. Benchmark data sets are thus required. This area is well developed for organic molecules and biomolecules but practically non-existent for boron clusters, which have been gaining in importance in modern drug as well as material design.

Bromination Mechanism of closo-1,2-C B H and the Structure of the Resulting 9-Br-closo-1,2-C B H Determined by Gas Electron Diffraction.

9-Br-closo-1,2-C B H has been prepared and its gas-phase structure has been examined by means of gas electron diffraction. The structure of the carbaborane core is similar to the structure of the parent compound, which is of C symmetry. A DFT-based search for the corresponding reaction pathway of the bromination of closo-1,2-C B H revealed that the catalytic amount of aluminum reduces the barrier of the initial attack of the bromination agent toward the negatively charged part of the icosahedral carbaborane, i.

Electrophilic Methylation of Decaborane(14): Selective Synthesis of Tetramethylated and Heptamethylated Decaboranes and Their Conjugated Bases.

The paper reports specific syntheses of methylated decaborane(14), -BH (), derivatives. The reaction of with an excess of neat MeI and AlCl yields 1,2,3,4-Me--BH () essentially quantitatively when performed at room temperature. Heating the same mixture to 120 °C provides 1-I-2,3,4,5,7,8,10-Me--BH ().

Face-Fusion of Icosahedral Boron Hydride Increases Affinity to γ-Cyclodextrin: closo,closo-[B H ] as an Anion with Very Low Free Energy of Dehydration.

The supramolecular recognition of closo,closo-[B H ] by cyclodextrins (CDs) has been studied in aqueous solution by isothermal titration calorimetry and nuclear magnetic resonance spectroscopy. These solution studies follow up on previous mass-spectrometric measurements and computations, which indicated the formation and stability of CD ⋅ B H complexes in the gas phase. The thermodynamic signature of solution-phase binding is exceptional, the association constant for the γ-CD complex with B H reaches 1.

The Influence of Halogenated Hypercarbon on Crystal Packing in the Series of 1-Ph-2-X-1,2-dicarba--dodecaboranes (X = F, Cl, Br, I).

Although 1-Ph2-X--1,2-CBH (X = F, Cl, Br, I) derivatives had been computed to have positive values of the heat of formation, it was possible to prepare them. The corresponding solid-state structures were computationally analyzed. Electrostatic potential computations indicated the presence of highly positive σ-holes in the case of heavy halogens.

Thiaboranes on Both Sides of the Icosahedral Barrier: Retaining and Breaking the Barrier with Carbon Functionalities.

The concept of icosahedral barrier has been expanded from the chemistry of carbaboranes to the area of thiaboranes. Both representatives of this barrier, i. e.

Photochromic System among Boron Hydrides: The Hawthorne Rearrangement.

Photoswitchable molecules have attracted wide interest for many applications in chemistry, physics, and materials science. In this work, we revisit the reversible photochemical and thermal rearrangements of the two BH isomers reported by Hawthorne and Pilling in 1966, whose mechanism had not been understood so far. We investigate the rearrangements by means of a joint experimental and computational study with the outcome that BH represents the first boron-based photochromic system ever reported.

Chalcogen Bonding due to the Exo-Substitution of Icosahedral Dicarbaborane.

Chalcogen atoms are a class of substituents capable of generating inner and outer derivatives of boron clusters. It is well known that chalcogenated boron clusters can form strong σ-hole interactions when a chalcogen atom is a part of an icosahedron. This paper studies σ-hole interactions of dicarbaboranes with two exopolyhedral chalcogen atoms bonded to carbon vertices.