Closo-borate Anions Research Articles

Synthesis of Triethylammonium Salts of Amidine Derivatives of closo-Borate Anions [B10H10]2– and [B12H12]2– and Study of Their Cytotoxic Properties

Synthesis of Triethylammonium Salts of Amidine Derivatives of closo-Borate Anions [B10H10]2– and [B12H12]2– and Study of Their Cytotoxic Properties

Study of Hydrophilic/Hydrophobic Properties of Borylated Iminols [BnHn – 1NHC(OH)R]– (n = 10, 12)

The behavior of borylated iminols based on the closo-decaborate and closo-dodecaborate anions in the dichloromethane–water system has been studied as a function of the pH of the aqueous phase. The distribution coefficients of compounds in the n-octanol–water system have been determined: for (Bu4N)[B12H11NHC(OH)CH3], log Kow = –0.46; for (Bu4N)[2-B10H9NHC(OH)CH3], log Kow = –0.51. These compounds show hydrophilic properties similar to those of formic and acetic acids. It has been shown that this method can be used to purify target compounds from hydrolysis products in the preparation of various derivatives as a result of nucleophilic addition of the closo-borate anions to nitrilium derivatives.

Synthesis of Disubstituted Carboxonium Derivatives of Closo-Decaborate Anion [2,6-B10H8O2CC6H5]-: Theoretical and Experimental Study.

A comprehensive study focused on the preparation of disubstituted carboxonium derivatives of closo-decaborate anion [2,6-B10H8O2CC6H5]- was carried out. The proposed synthesis of the target product was based on the interaction between the anion [B10H11]- and benzoic acid C6H5COOH. It was shown that the formation of this product proceeds stepwise through the formation of a mono-substituted product [B10H9OC(OH)C6H5]-. In addition, an alternative one-step approach for obtaining the target derivative is postulated. The structure of tetrabutylammonium salts of carboxonium derivative ((C4H9)4N)[2,6-B10H8O2CC6H5] was established with the help of X-ray structure analysis. The reaction pathway for the formation of [2,6-B10H8O2CC6H5]- was investigated with the help of density functional theory (DFT) calculations. This process has an electrophile induced nucleophilic substitution (EINS) mechanism, and intermediate anionic species play a key role. Such intermediates have a structure in which one boron atom coordinates two hydrogen atoms. The regioselectivity for the process of formation for the 2,6-isomer was also proved by theoretical calculations. Generally, in the experimental part, the simple and available approach for producing disubstituted carboxonium derivative was introduced, and the mechanism of this process was investigated with the help of theoretical calculations. The proposed approach can be applicable for the preparation of a wide range of disubstituted derivatives of closo-borate anions.

Theoretical Insight into B–C Chemical Bonding in Closo-Borate [BnHn−1CH3]2− (n = 6, 10, 12) and Monocarborane [CBnHnCH3]− (n = 5, 9, 11) Anions

A theoretical investigation of mono-methyl derivatives of closo-borate anions of the general form [BnHnCH3]2– (n = 6, 10, 12) and monocarboranes [HCBnHnCH3]− (n = 5, 9, 11) was carried out. An analysis of the main bonding descriptors of exo-polyhedral B–C bonds was performed using the QTAIM (quantum theory of “Atoms in Molecules”), ELF (electron localisation function), NBOs (natural bond orbitals) analyses and several other approaches for the estimation of B–C bond orders (viz. Laplacian bond order (LBO), fuzzy bond order (FBO) and Mayer and Wiberg formalisms). Based on the data obtained on electron density descriptors, it can be concluded that orbital interaction increases with increasing boron cluster size. The present investigation provides a better understanding of exo-polyhedral B–C bond phenomena in boron cluster systems. The data obtained can be used to estimate B–C bond strength, which can be useful for studies devoted to the synthesis and properties of boron cluster systems.

Nucleophilic Addition of Polyfunctional Amines to Acetonitrile Derivatives of closo-Borate Anions [BnHn – 1NCCH3]– (n = 10, 12)

Nucleophilic Addition of Polyfunctional Amines to Acetonitrile Derivatives of closo-Borate Anions [BnHn – 1NCCH3]– (n = 10, 12)

Study of Spin-Crossover in Iron(II) Complexes with 2,6-Bis(4,5-Dimethyl-1H-Imidazol-2-yl)Pyridine and closo-Borate Anions

New iron(II) coordination compounds with 2,6-bis(4,5-dimethyl-1H-imidazol-2-yl)pyridine (L) and closo-borate(2–) anions [FeL2]B10H10⋅2H2O and [FeL2]B12H12⋅H2O have been synthesized. The compounds have been identified and studied by CHN analysis, electron spectroscopy (diffuse reflection spectroscopy), IR, Mössbauer, and EXAFS spectroscopies, X-ray powder diffraction, and static magnetic susceptibility. The structures of the coordination knots of complexes [FeL2]B10H10⋅2H2O and [FeL2]B12H12⋅H2O has been obtained by modeling the EXAFS spectra. The ligand is coordinated by the iron(II) ion in a tridentate-cyclic manner by two nitrogen atoms of imidazole cycles and a nitrogen atom of pyridine to form the FeN6 coordination knot. The study of the temperature dependence of the magnetic susceptibility in the range of 80–500 K has showed that the high-temperature spin-crossover 1А1 ↔ 5Т2 manifests itself in the obtained compounds.

B-F bonding and reactivity analysis of mono- and perfluoro-substituted derivatives of closo-borate anions (6, 10, 12): A computational study

A theoretical study of the mono- and perfluoro-substituted derivatives of closo-borate anions with the general form [BnHn-1F]2– and [BnFn]2–, n = 6, 10, 12, was carried out. The main features of B-F bonds in selected molecular species were investigated using a number of general approaches (QTAIM, NBO, ELF). Atomic charges were estimated using AIM, NBO and Hirshfeld approaches. Global and local reactivity indices were calculated using Conceptual DFT theory.

Theoretical Study of closo-Borate Anions [BnHn]2− (n = 5–12): Bonding, Atomic Charges, and Reactivity Analysis

This study has focused on the structure, bonding, and reactivity analysis of closo-borate anions [BnHn]2− (n = 5–12). Several descriptors of B–H interactions have been calculated. It has been found that the values of electron density and total energy at bond critical point are the most useful descriptors for investigation of B–H interactions. Using results from the descriptor analysis, one may conclude that orbital interactions in [BnHn]2− increase with increasing the boron cluster size. Several approaches to estimate atomic charges have been applied. Boron atoms in apical positions have more negative values of atomic charges as compared with atoms from equatorial positions. The mean values of boron and hydrogen atomic charges tend to be more positive with the increasing of boron cluster size. Global and local reactivity descriptors using conceptual density functional theory (DFT) theory have been calculated. Based on this theory, the closo-borate anions [BnHn]2− (n = 5–9) can be considered strong and moderate electrophiles, while the closo-borate anions [BnHn]2− (n = 10–12) can be considered marginal electrophiles. Fukui functions for electrophilic attack have been calculated. Fukui functions correlate well with atomic charges of the closo-borate anions. Boron atoms in apical positions have the most positive values of Fukui functions.

High-Temperature Spin Crossover in Complexes of Iron(II) closo-Borates with 2,6-Bis(benzimidazol-2-yl)pyridine

New iron(II) complexes with 2,6-bis(benzimidazol-2-yl)pyridine (L) and closo-borate(2–) anions—[FeL2][B10H10] ⋅ 2H2O and [FeL2][B12H12] ⋅ H2O—have been synthesized. The complexes have been characterized by static magnetic susceptibility measurements, electronic (diffuse reflectance spectra), IR, and EXAFS spectroscopy, and X-ray diffraction analysis. A study of the μeff(T) dependence in the temperature range 80–500 K has shown that the complexes exhibit a high-temperature spin crossover 1А1 ⇔ 5Т2.

Theoretical study of closo-borate derivatives of general type [BnHn-1COR]2– (n = 6, 10, 12; R = H, CH3, NH2, OH, OCH3) – Borylated analogue of organic carbonyl compounds

This study is focused on the structure, bonding, and reactivity analysis of the derivatives of closo-borate anions [BnHn-1COR]2– (n = 6, 10, 12; R = H, CH3, NH2, OH, OCH3). The phenomena of B–C bonding interactions in the [BnHn-1COR]2– (n = 6, 10, 12; R = H, CH3, NH2, OH, OCH3) have been theoretically studied by using the Quantum Theory of Atoms in Molecules analysis. Several local and integral topological properties of the electron density involved in these interactions have been computed. Also, different chemical reactivity descriptors have been calculated via conceptual density functional theory.

Closo-Borate Derivatives of General Type [Bnhn-1cor]2– (N=6,10,12; R= H, Ch3, Nh2, Oh, Och3) – Borylated Analogue of Organic Carbonyl Compounds: B–C Bonding, Non-Covalent Interactions, and Reactivity Analysis

This study is focused on the structure, bonding, and reactivity analysis of the derivatives of closo-borate anions [BnHn-1COR]2– (n=6,10,12; R= H, CH3, NH2, OH, OCH3). The phenomena of B–C bonding interactions in the [BnHn-1COR]2– (n=6,10,12; R= H, CH3, NH2, OH, OCH3) have been theoretically studied by using the Quantum Theory of Atoms in Molecules. Several local and integral topological properties of the electron density involved in these interactions have been computed. Also, different chemical reactivity descriptors have been calculated via conceptual density functional theory.

Theoretical study of monocarbonyl derivatives of closo-borate anions [BnHn–1CO]– (n = 6, 10, 12): bonding and reactivity analysis

The structure, bonding, and reactivity of the monocarbonyl derivatives of closo-borate anions [BnHn–1CO]– (n = 6, 10, 12) have been analyzed. The B–B, B–H, B–C and C–O bonding interactions in such anions have been theoretically examined using the Quantum Theory of Atoms in Molecules (QTAIM). Several local and integral topological properties of the electron density involved in these interactions have been computed, and different chemical reactivity descriptors have been calculated via conceptual density functional theory (DFT).

QTAIM Analysis of Mono-Hydroxy Derivatives of closo-Borate Anions [BnHn– 1OH]2– (n = 6, 10, 12)

This theoretical study focused on the structure of mono-hydroxy derivatives of closo-borate anions and nature of bonding interactions in these species. DFT calculations at the ωB97X-D3/6-31++G(d,p) level of theory have been performed and B–B, B–H, B–O, and O–H bonding interactions in the mono-hydroxy derivatives of closo-borate anions [BnHn – 1OH]2– (n = 6, 10, 12) have been studied under the perspective of the Quantum Theory of Atoms in Molecules (QTAIM) and several local and integral topological properties of the electron density involved in these interactions.

Dihydrogen Bonds in Salts of Boron Cluster Anions [BnHn]2− with Protonated Heterocyclic Organic Bases

Dihydrogen bonds attract much attention as unconventional hydrogen bonds between strong donors of H-bonding and polyhedral (car)borane cages with delocalized charge density. Salts of closo-borate anions [B10H10]2− and [B12H12]2− with protonated organic ligands 2,2’-dipyridylamine (BPA), 1,10-phenanthroline (Phen), and rhodamine 6G (Rh6G) were selectively synthesized to investigate N−H...H−B intermolecular bonding. It was found that the salts contain monoprotonated and/or diprotonated N-containing cations at different ratios. Protonation of the ligands can be implemented in an acidic medium or in water because of hydrolysis of metal cations resulting in the release of H3O+ cations into the reaction solution. Six novel compounds were characterized by X-ray diffraction and FT-IR spectroscopy. It was found that strong dihydrogen bonds manifest themselves in FT-IR spectra that allows one to use this technique even in the absence of crystallographic data.

Gas phase fragmentation of adducts between dioxygen and closo-borate radical anions

The icosahedral closo-borate anions, [closo-B12X12]2− (B12) and [1-H-closo-1-CB11X11]− (CB11) with X=H or halogen, are exceptionally stable weakly coordinating anions. Recent studies, which focused on the gas phase ion chemistry of this class of anions, revealed several unusual ion-molecule and unimolecular dissociation pathways. Herein, we demonstrate that collisional activation of highly iodinated closo-borate anions results in a loss of an iodine atom followed by a spontaneous addition of O2 present in a mass spectrometer background producing B12-O2 and CB11-O2 species. We examined the electronic structure of a representative O2 adduct using photoelectron spectroscopy and explored collision-induced dissociation (CID) pathways of a series of iodinated B12-O2 and CB11-O2 anions with different substituents. A systematic study of the gas phase dissociation pathways of the B12-O2 and CB11-O2 anions revealed several unusual dissociation pathways characteristic of this class of species. Abundant fragment ions are formed by neutral loss of BOX2 (X = boron bound substituent), Y2H (Y = boron bound halogen, if any H is present in the molecular ion) and BO2. Loss of BO2 was observed for CB11-O2 but not for B12-O2 anions. Substantial differences in stability of the corresponding fragments are responsible for the observed differences in dissociation of B12-O2 and CB11-O2 species. Furthermore, we show that in addition to O2 other molecules with a radical character (e.g. SCH3) can form adducts with closo-borate anions after iodine abstraction. The boron cage fragmentation observed for the O2 adducts is atypical for highly iodinated closo-borates and is attributed to the strength of BO bonds which dominate the thermochemistry of B12-O2 and CB11-O2 fragmentation reactions.

Low-temperature composite lubricants with anticorrosion properties, based on compounds of closo-borate anions [BnHn]2- and ammonio-derivatives [BnHn-1NH3] - (n = 10, 12) of them

Low-temperature composite lubricants with anticorrosion properties, based on compounds of closo-borate anions [BnHn]2- and ammonio-derivatives [BnHn-1NH3] - (n = 10, 12) of them

Structure, physicochemical properties, and reactivity of the [B9H9]2– anion

Data on the structure, properties, and reactivity of one of the least studied 3D aromatic clusters—nonahydro-closo-nonaborate anion [B9H9]2–—have been systematized. It has been shown that the key aspects of its reactivity are related to structural flexibility, which essentially distinguishes the [B9H9]2– anion from the higher representatives of closo-borate anions.

Solid State Li Ion Batteries with Monocarba-Closo-Decaborate Solid Electrolytes

Solid state rechargeable batteries with high energy and power density as well as safety, reliability and long cycle life remain a long standing goal for the energy storage community. While many solid electrolytes have recently been demonstrated with ionic conductivities approaching those of liquid electrolytes at room, few have been integrated into full batteries with competitive power performance. Recently, we discovered a novel class of superionic solid electrolytes, whose facile cation conduction pathways are enabled by the spacious, vacancy-rich, interstitial network created by a sublattice of polyhedral, orientationally mobile, monocarba closo-borate anions and which form salts with alkali metals, LiCB11H12 and LiCB9H10 [1, 2]. These electrolytes exhibit conductivities of ~10-5 S/cm at room temperature and ~0.03 S/cm at 345 C. In this talk we will describe the fabrication and testing of complete batteries consisting of thick film LiCoO2 cathodes with theoretical capacity of ~1.5 mAhrs/cm2 and metallic Li anodes. 1. W. S. Tang, A. Unemoto, W. Zhou, V. Stavila, M. Matsuo, H. Wu, S. Orimo, and T. J. Udovic, Energy Environ. Sci., 2015, doi: 10.1039/c5ee02941d. 2. W. S. Tang, M. Matsuo, H. Wu, V. Stavila, W. Zhou, A. A. Talin, A. V. Soloninin, R. V. Skoryunov, O. A. Babanova, A. V. Skripov, A. Unemoto, S. Orimo, and T. J. Udovic, Adv. Ener. Materials, in review.

Synthesis and reactivity of closo-decaborate anion derivatives with multiple carbon–oxygen bonds

Some methods of functionalization of closo-borate anions on the example of the interaction with carboxylic acids are considered. Oxonium derivatives of closo-decaborate anion [2-B10H9OC(OR)CH3]− (R=H, Et) were prepared and transformed upon subsequent heating into 2,6-disubstituted derivative [2,6-B10H8(O2CCH3)]−. The obtained compounds were characterized by IR and NMR (1H, 11B, 13C) spectroscopies. The crystal structure of (Bu4N)[2,6-B10H8(O2CCH3)] was determined by X-ray diffraction.

Iron(II) closo-borate complexes with 1,2,4-triazole derivatives: Spin crossover in the iron(II) closo-borate complexes with tris(pyrazol-1-yl)methane

Methods of synthesis of iron(II) complexes containing cluster closo-borate anions—[Fe(Htrz)3]B10Cl10 (I) (HTrz is 1,2,4-triazole), [Fe(NH2Trz)3]B10Cl10 · 2H2O (II) (NH2Trz is 4-amino-1,2,4-triazole), [Fe{HC(pz)3}2]B10Cl10 (III), [Fe{HC(pz)3}2]B10H10 (IV), and [Fe{HC(pz)3}2]B12H12 · 2H2O (V) (HC(pz)3 is tris(pyrazol-1-yl)methane)—have been developed. The compounds have been studied by the static magnetic susceptibility method (78–500 K) and electronic, IR, and EXAFS spectroscopy. Complexes I and II in the temperature range under consideration remain in the high-spin state. Low-spin complex III shows incomplete spin crossover and decomposes on heating above 440 K. Complexes IV and V are characterized by reversible spin crossover 1 A 1 ⇔ 5 T 2 accompanied by thermochromism (the pink ⇔ white color change). The crossover temperature (T c) for IV and V is 375 and 405 K, respectively.