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The dependence of the electronic properties of 1-o-, 3-o- and 1-m-carboranyl groups on the type of solvent has been studied using Taft's method. The electron-attraction effect of the 1-o- and 3-o-carboranyl groups changes with hydrogen bond formation between the acidic hydrogens of the o-carborane nucleus and the proton-attracting solvent. The electronic properties of the 1-m-carboranyl group are practically solvent-independent. The electron-attraction abilities of the 1-o- and 3-o-carboranyl groups in various solvents are determined by changes in the inductive effect (σ1), whereas the resonance effect (σOR) remains practically constant. Substitution with methyl groups of the acidic hydrogens in the 1-o-, 3-o- and 1-m-carboranyl groups does not alter the dependence of the electronic properties on the solvents; this shows an absence of noticeable donor-acceptor interaction between the boron skeleton of carboranes and the proton-accepting and -donating solvents. It has been stated that the carboranyl groups display rather small accepting conjugative effects (σOR > 0) while a negligible donating conjugative effect is observed (σOR

1. The concentration equilibrium constants of the reactions of metalation of the CH bonds of o- and m-barene and their methyl- and phenyl-derivatives by carbanions of a number of hydrocarbons and phenylxanthene in 1,2-dimethoxyethane were determined by spectrophotometric measurements, and the values of pKa of the thermodynamic acidities of barenes were calculated. 2. An estimate of pKa of 1-methyl-o-barenes, followed by bromination and carbonization of equilibrium systems and the use of gas-liquid chromatography. 3. The kinetic acidities of the CH bonds of m-barene and its methyl- and phenyl-derivatives were determined by measuring the kinetics of the reactions of isotopic exchange of hydrogen with liquid deuterated ammonia. 4. The higher acidity of o-barenes in comparison with m-barenes was confirmed. 5. The possible influence of specific solvation on the value of pKa of barenes was hypothesized.

1. The heats of combustion, formation, and sublimation of o- and m-carboranes were determined. 2. The difference in the energies of formation of o- and m-carboranes, equal to 16 kcal/mole, was found experimentally. 3. It was confirmed experimentally that o-carborane is thermodynamically less stable than m-carborane.

1. In an investigation of the PMR spectra of methylmercury derivatives of ortho-, meta-, and paracarboranes, substantial variations of the spin-spin interaction constants JHg199-C-H1 were found as a function of the structure of the compound and the nature of the medium. 2. The values of JHg199-C-Hg1 in substituted ortho-carboranes\(\begin{array}{*{20}c} {R - C - C - HgCH_3 } \\ {\begin{array}{*{20}c} \backslash & / \\ \end{array} } \\ {B_{10} H_{10} } \\ \end{array}\) are satisfactorily correlated with the induction constants of the substituents R. 3. The sensitivity of the indicator group HgCH3 to the polar influence of substituted ortho-carboranes depends on the solvent, decreasing in the series CH2Cl2>dioxane>pyridine >dimethyl sulfoxide. 4. The presence of intramolecular coordination of certain substituents (R=C6H5CH2, CH3OCH2) with the metal atom of the indicator group HgCH3 was ascertained in substituted ortho-carboranes. 5. The sequence of increasing electronegativity of certain carboranyl radicals was established: $$\begin{array}{*{20}c} {o - HCB_{10} H_{10} C - CH_2< p - HCB_{10} H_{10} C -< m - HCB_{10} H_{10} C - } \\ {< m - PB_{10} H_{10} C -< o - HCB_{10} H_{10} C -< o - CH_3 - C(3 - F)B_{10} H_9 C -< o - CH_3 - C(9,12 - Cl_2 )B_{10} H_8 C - .} \\ \end{array}$$ 6. The dependence of the electron donor properties of the CH3Hg group on the selection of the solvent was demonstrated.

1. The electrophilic monohalogenation of barene proceeds predominantly in the 9(12)-position of the barene nucleus, in which connection 3–10% of the 8-halobarene is formed. 2. The electrophilic monohalogenation of 1-methylbarene proceeds to equal degree in the 9- and 12-positions of the barene nucleus with the formation of the 1-methyl-9- and 1-methyl-12-halobarenes, in which connection 5–10% of the 1-methyl-8-halobarene is also formed. 3. Together with the predominant formation of the 9, 12-isomer, appreciable amounts of the 8, 9-isomer (20–30%) and a trace amount of the 8,10-isomer (1%) are formed in the electrophilic dihalogenation of barene and 1-methylbarene. 4. The electrophilic halogenation of neobarene proceeds more selectively than in the case of barene, and leads to the formation of mainly the 9(10)-halobarene and 9,10-dihalobarene. 5. All of the possible monohaloneobarenes are formed in the radical halogenation of neobarene.

1. Neobarenes are isomerized to barenes via the dianions of the dicarbadodecaboranes (14), in which connection the isomerization must be regarded as being a three-step process: a) reduction, b) isomerization of the dianion, and c) oxidation. 2. The dianions of the dicarbadodecaboranes (14) form barenes when treated with oxidizing agents. 3. The rapid addition of two equivalents of the metal occurs when the neobarenes are treated with alkali metals in liquid ammonia, with the formation of the adduct (m-B10H10C2RR′)2M, which is easily isomerized to the adduct (o-B10H10C2RR′)2M. 4. The transfer of two electrons to the barene or neobarene nucleus occurs when the barenes or neobarenes are treated with aromatic anion-radicals of the type of naphthalenesodium in tetrahydrofuran solution, with the formation of the dianions.

The equilibrium and kinetic acidities of the methines of isomeric carboranes and of some of their derivaties in several solvents have been determined. Calculated p K a values were successfully correlated with Streitwieser's hydrocarbon acidity scale. The kinetics and activation parameters of hydrogen isotopic exchange have been measured. The absence of a deuterium-tritium kinetic isotope effect has been shown. The rate constants of reversible metallation of 1-alkyl- o -carboranes have been determined.

1. 3-Aminocarboranes have been prepared using the dicarbadodecarborane(14) dianion—the products obtained by the addition of two electrons to the carborane molecule in liquid ammonia. 2. 3-Aminocarboranes exhibit the properties characteristic of aliphatic and aromatic amines: they form salts with acids, and may be alkylated, acylated and diazotized. 3. 3-Halocarboranes, including 3-fluorocarboranes, have been prepared via the diazonium salts of 3-aminocarboranes.

A. simple procedure for the preparation of 1, 2–dicarbacloso-dodecaboran(12)-3-ylcarboxylic acids from the readily available 3-amino-1, 2-dicarba-closo-dodecabo-rane(12) has been developed.

1. The thermal rearrangement of the halogen in 9-halobarenes and 9-haloneobarenes yields all of the possible B-halobarenes and B-haloneobarenes. 2. The thermal rearrangement rate of the halogen in the 9-haloneobarenes is considerably slower than that of the halogen in the 9-halobarenes. 3. The rearrangement rate of the halogen in the haloneobarenes depends on the nature of the halogen. 4. The isomerization of the 9,12-dihalobarene, 8, 9,12-trihalobarene and 8, 9,10,12-tetrahalobarene proceeds with the formation of mixtures containing most of the corresponding isomeric haloneobarenes. 5. It was shown that the intermolecular exchange B-H+B-I⇌B-I+B-H takes place in the barenes. 6. The rate with which the hydrogen atom in the different positions of the neobarene nucleus is replaced during electrophilic halogenation decreases in the order: 9,10≫5,12>4,7,8,11≫2,3.

1. The IR spectra of compounds of the barene and neobarene series were obtained, and the assignment of certain frequencies was given. 2. The integral intensity of the band corresponding to the characteristic valence C-H vibration (ICH) was measured in the IR spectra of more than 50 compounds. 3. Successive introduction of halogen atoms at the boron atoms of the barene and neobarene ring leads to a gradual increase in ICH. 4. The influence of the substituent X in the system o-XCB10H10CH upon the C-H bond is transmitted according to an induction mechanism. A linear relationship between √ICH and the induction constant σi of the substituent X was found. The value derived for σi for the CH2Hg group is −0.20.

2-Substituted m-carboranes containing carboxyl, amino and hydroxyl groups at the boron atom of the m-carborane nucleus are synthesized by a simple procedure from 2-vinyl-m-carborane.

1. In a study of the comparative reactivity, it was shown that the acidity of the C-H bonds, the electron-acceptor effects of the ring, the ease of electrophilic, radical, and exchange halogenation, the stability of the carboranyl anion, the rate of nucleophilic substitution, the electron affinity of the carborane system, and the rate of cleavage of the C-C bonds in carbonyl derivatives under the action of nucleophilic reagents decrease in the series of o-, m-, and p-carboranes, and the stability to the action of strong bases and oxidizing agents increases. 2. 1-p-Carboranecarboxylic and 1,12-p-carboranedicarboxylic acids were produced by carbonization of mono- and dilithium derivatives of p-carboranes. 3. In the electrophilic halogenation of p-carborane, 2-bromo-p-carborane, and 2-chloro-p-carborane were produced. 4. In the photochlorination of p-carborane, decachloro-p-carborane, p-B10C10C2H2, was produced. 5. The value of the dissociation constant (pK a =3.64) in 50% alcohol was determined for 1-p-carboranecarboxylic acid. 6. The value of the equilibrium acidity (pK a =29.8–29.9 in the McEwen scale) was determined for p-carborane. 7. α-Ketones of the p-carborane series undergo cleavage of the C-C bond under the action of bases. 8. The thermal isomerization of m-carborane to p-carborane is an equilibrium reaction.

The Taft method was used to measure the induction constant for the 1-p-carboranyl group (σi = +0.14). It was shown that this group is an electron-acceptor grouping.

1. The spectral characteristics of the C-H valence vibration bands of o-, m-, and p-carboranes have been studied in CCl4 and DMSO solutions. 2. o-, m-, and p-Carboranes form H-bonded complexes of the type RCB10H10CH...O with DMSO. The enthalpy of formation of these complexes, calculated according to the formulae of Iogansen from the frequencies and intensities of the νC-H bands, amounts to 2–3 kcal/mole. 3. The introduction of halogen atoms to the carborane nucleus leads to an increase in the stability of the H-bonded complex in comparison with the unsubstituted carboranes.

1. Polarographic reduction of C-hydrocarbon derivatives and B-haloderivatives of barenes and neobarenes was studied. 2. The barene system has a greater electron affinity than does the neobarene system.

1. The reactions of 1-bromomagnesiomethylbarene with HgCl2, SnCl4, and PCl3 have given di(barenylmethyl)mercury, tetra(barenylmethyl)tin, and tri(barenylmethyl)phosphine. 2. The action of 1-bromomagnesiomethylbarene on (π-C5H5)2TiCl2 has given the stable di(π-cyclopentadienyl)di(σ-barenylmethyl)titanium.

1. The dianion of dicarbadodecaborane (14) is capable of donating electrons to such electron acceptors as p-quinone, benzophenone, fluorenone, and nitrobenzene, giving o-carborane and the corresponding anion radicals of the electron acceptors. 2. There is a transfer of electrons from the dianion of dicarbadodecaborane (14) to substituted o-carborane (1,2-diphenyl-o-carborane, 1-vinyl-o-carborane, and 1-phenyl-o-carborane). 3. The dianion of dicarbadodecaborane (14) reduces the C-Br bond in bromoform and carbon tetrabromide.

1. The bromine and iodine atoms in bromo- and iodobarenes and neobarenes are exchanged by chlorine upon heating them with CuCl. 2. The reactivity of the halogen in barene and neobarene halides is considerably lower compared to the halogen derivatives of a number of benzenes and ferrocenes.

1. The spin-spin coupling constants J199Hg-C-1H were determined for a series of methylmercuric carboranecarboxylates, ferrocenecarboxylate, and cyclopentadienylmanganesetricarbonylcarboxylate. 2. A relation was found between the J199Hg-C-1H values for the methylmercuric carboxylates RCOOHgCH3 and the Taft σ* constants. On the basis of this relation σ* values were calculated for the l-o-, 1-m-, and 1-p-carboranyl groups, ferrocenyl groups, and cyclopentadienylmanganesetricarbonyl groups. 3. The dissociation constants pKa for l-o-, 1-m-, and 1-p-carboranecarboxylic acids were calculated from the JHg-CH3 values.

1. Using the Taft method it was shown that the 1-[1,8-dicarbaclosoundecaborane (11)] group is an electron-acceptor grouping, which exhibits only an induction effect (induction constantσi=0.12; resonance constantσR0=0.00). 2. The opening of the carborane structure to the anion of m-dicarbaundecaborane is postulated when the adduct of 1,8-dicarbaclosoundecaborane (11) with triphenylphosphine is formed, in which connection this grouping exhibits electron-donor properties (σi=−0.24;σR0=−0.15).

1. Anions of neodicarbaundecaboranes(13) are formed smoothly by heating neobarenes with caustic potash in butyl and amyl alcohols, methyl- and ethylcellosolves, and ethylene glycol. 2. On the basis of the oxidative cleavage of phenylneodicarbaundecaborane(13) and phenyldicarbaundecaborane(13), which leads to identical products (tolune, ethylbenzene, styrene, phenylacetylene, benzaldehyde, and acetophenone), the idea of a mutual rearrangement of the ortho and meta structures in the intermediate products of the oxidation of derivatives of neodicarbaundecaborane(13) and dicarbaundeca-borane(13) has been proposed.

1. The double bond in 1-vinylbarene is capable of taking part in electrophilic addition reactions, although it has a considerably lower reactivity thanα-olefins. 2. Hydrogen chloride and bromide add to vinylbarene in the presence of AlCl3 according to Markovnikov's rule with the formation of 1-(α-chloroethyl)barene and l-(α-bromoethyl)barene, respectively. 3. The barene and neobarene nuclei undergo thermal chlorination, which takes place similarly to photochemical chlorination.

A series of new derivatives of phenylbarene and phenylneobarene, substituted in the benzene ring, were obtained.

1. We obtained the UV absorption spectra of 1-phenyl-o-carborane, 3-phenyl-o-carborane, 1-phenyl-m-carborane, 1,2-diphenyl-o-carborane, 1,7-diphenyl-m-carborane, and also the cesium salt of phenyldi-carbaundecarborane (13) in the 210–340 nm region. 2. The integral intensity of the ∼1600 cm−1 line in the Raman spectra of solutions of 1-phenyl-o-carborane, 1,2-diphenyl-o-carborane, 1-phenyl-m-carborane, and benzotrifluoride in CH2Cl2 was measured. 3. The effect of the carborane nucleus on the UV absorption band of the benzene ring in the 240–280 nm region is expressed in a slight shift of the maximum, with the retention of a distinct vibrational structure and an increase in the molar absorption coefficient up to several hundred units. In contrast, in the UV spectrum of [C6H5CB9H10CH]−Cs+ the intensity of the same band reaches 7700; the vibrational structure is smoothed out completely. 4. On the basis of the UV spectra and the intensities in the Raman spectra of the phenylcarboranes it was concluded that conjugation of the benzene ring with carborane nuclei is absent, and that conjugation with the dicarbaundecarborane (13) anion exists.

1. It was shown on the basis of the reactions of C-bromo- and C-iodo-neobarenes with alcoholic alkali that the bromine and iodine atoms in these compounds have a “positive” character. 2. C-bromo- and C-iodo-neobarenes undergo ready metal-halogen interchange with butyllithium and ethylmagnesium bromide. 3. C-bromo- and C-iodo-barenes undergo ready metal-halogen exchange with butyllithium and ethylmagnesium bromide.

1. The electrophilic halogenation of neobarene leads to the formation of two isomeric B-dihaloneobarenes. B-Hexahaloneobarenes are formed on further halogenation. 2. The electrophilic iodination of barene and neobarene goes at the boiling point of CCl4. 3. The exhaustive electrophilic chlorination of phenylbarene gives 1-pentachlorophenyl-8,9,10,12-tetrachlorobarene.

1. A halogen on the carbon atoms of carborane and neocarborane nuclei migrates upon heating to boron atoms with the formation of carborane and B-halocarboranes, and neocarborane and B-haloneocarboranes, respectively. 2. The halogen in the side chain of 1-halomethylcarboranes is able to migrate upon heating to boron atoms, giving 1-methylcarborane and 1-methyl-B-halocarboranes. 3. The B-H bonds of carborane and neocarborane nuclei possess reductive properties.

1. The electronic influence of the 1-[1,6-dicarbalkosodecaborane(10)] (induction constant σi=0.10 and resonance constant σR0=−0.02) and 1-[1,10-dicarbalkosodecaborane(10)] groups (σi=0.05 and σR0=−0.02), which play the role of weak electron-acceptor groups, is manifested chiefly according to an inductive mechanism. 2. The nitration of 1-phenyl-1,10-dicarbalkosodecaborane(10) proceeds primarily in the p-position of the benzene ring.

1. Starting from lithium-p-carboranes, the C-iodo-, mercapto-, benzoyl-, methylmercury-, ni-troso-, and amino-derivatives of p-carborane were obtained, p-Carboranesulfinic acid was also produced. 2. Iodine atoms in C-iodo-p-carborane have a “positive” character. 3. The reactivity of lithium-p-carborane is analogous to that of lithium-m-carborane.

The corresponding B-halobarenes, with a definite position of the halogen atom in the barene nucleus, were synthesized from the 1-chloro-, 2-chloro-, 2-bromo-, 1-iodo- and 2-iododecaboranes by reaction with acetylene, phenylacetylene and propargyl bromide.

Die Lithium-o-carborane (I) und das Lithium-m-carboran (IV) reagieren in absolutem Ather mit trockenem Benzoldiazoniumfluoroborat (II) zu den Phenylazocarboranen (III) und (V), die katalytisch uber Palladium /Bariumsulfat oder Raney-Nickel leicht zu den Hydrazinen (VI) und (VII) hydriert werden kfonnen.

Mit dem Lithiumderivat des l-Phenyl-1,10-dicarbac1ovodecaborans(l0) (II) werden folgende Umsetzungen durchgefuhrt: Quecksilber(l)-bromid und Methylquecksilberbromid geben die Verbindungen (I) und (III).

The 1-(4′-acetylphenyl)-o- and m-carboranes are capable of trimerizational cyclocondensation to give 1,3,5-tri-[(4-carboranyl)-phenyl]benzenes.