Icosahedral Carboranes

Grimes, Russell N.

doi:10.1016/b978-0-12-801894-1.00009-3

Cited by 33 publications

(25 citation statements)

References 1,313 publications

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“…The reactions of the prepared arylzinc bromides with 9-iodo-ortho-carborane in the presence of 2 mol.% of [(Ph 3 P) 2 PdCl 2 ] in acetonitrile at room temperature lead to its nearly quantitative conversion to the corresponding 9-aryl-ortho-carboranes with isolated yields varying from 60 to 91% (Schemes 2 and 3). The synthesized 9-aryl-ortho-carboranes were characterized by the methods of 1 H, 13 C and 11 B NMR and IR spectroscopy. The 1 H and 13 C NMR spectra of all compounds contain signals of the corresponding aryl substituents as well as the signals of two non-equivalent carborane CH groups in the range of 3.3-3.7 ppm and 48-53 ppm, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…The solid-state structures of all new 9-aryl-ortho-carboranes (except for 6, which is liquid) were determined by single crystal X-ray diffraction (Figures 2 and 3). The synthesized 9-aryl-ortho-carboranes were characterized by the methods of 1 H, 13 C and 11 B NMR and IR spectroscopy. The 1 H and 13 C NMR spectra of all compounds contain signals of the corresponding aryl substituents as well as the signals of two non-equivalent carborane CH groups in the range of 3.3-3.7 ppm and 48-53 ppm, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…9-(2-Cyanophenyl)-ortho-carborane (7): 2-Cyanophenyl bromide (455 mg, 2.50 mmol) was used; mixture of chloroform and hexane (1:1, v/v) was used as eluent for column chromatography; a pale-yellow crystalline solid was obtained (184 mg, yield 75%). 1 H NMR (400 MHz, CDCl 3 ): δ 7.58 (2H, m, CH Ar ), 7.42 (1H, dd, J 1 = 7.7 Hz, J 2 = 7.5 Hz, CH Ar ), 7.29 (1H, dd, J 1 = 7.7 Hz, J 2 = 9.6 Hz, CH Ar ), 3.72 (1H, br s, CH Carb ), 3.65 (1H, br s, CH Carb ) ppm; 13 hkl for all 3308 independent reflections with 2θ < 56.1 • , (GOF = 1.066, R = 0.0445 calculated on F hkl for 2835 reflections with I > 2σ(I)). 9-(4-Cyanophenyl)-ortho-carborane (8): 4-Cyanophenyl bromide (455 mg, 2.50 mmol) was used; a mixture of chloroform and hexane (3:1, v/v) was used as eluent for column chromatography; a pale-yellow crystalline solid was obtained (221 mg, yield 90%).…”

Section: General Synthetic Procedures and Characterization Of Monosubsmentioning

confidence: 99%

“…Since the properties of the CH and BH groups in carboranes differ significantly, different methods are used to synthesize their Cand B-aryl derivatives. There are several methods for synthesis of C-arylcarboranes, where an aryl group is directly bonded to the cage carbon [13]. A general method involves the use of decaborane nido-B10H14 and reacting it with Lewis bases, such as dialkyl sulfides, acetonitrile or alkylamines.…”

Section: Introductionmentioning

confidence: 99%

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One-Pot Synthesis of B-Aryl Carboranes with Sensitive Functional Groups Using Sequential Cobalt- and Palladium-Catalyzed Reactions

et al. 2020

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The simple and efficient method was developed for the one-pot synthesis of B-substituted aryl derivatives of ortho-carborane with functional groups sensitive to organolithium and organomagnesium reagents using 9-iodo-ortho-carborane and generated in situ organozinc compounds. The method proposed was used to prepare a series of 9-aryl-ortho-carboranes, including those containing nitrile and ester groups, 9-RC6H4-1,2-C2B10H11 (R = p-Me, p-NMe2, p-OCH2OMe, o-OMe, p-OMe, o-CN, p-CN, o-COOEt, m-COOEt, and p-COOEt). It was demonstrated that the same approach can be used for synthesis of diaryl derivatives of ortho-carborane 9,12-(RC6H4)2-1,2-C2B10H10 (R = H, p-Me). The solid-state structures of 9-RC6H4-1,2-C2B10H11 (R = p-NMe2, p-OCH2OMe, o-OMe, o-CN, p-CN, m-COOEt, and p-COOEt) and 9,12-(p-MeC6H4)2-1,2-C2B10H10 were determined by single crystal X-ray diffraction.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: General Synthetic Procedures and Characterization Of Monosubsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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One-Pot Synthesis of B-Aryl Carboranes with Sensitive Functional Groups Using Sequential Cobalt- and Palladium-Catalyzed Reactions

et al. 2020

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“…Icosahedral dicarboranes exist in all three isomers (ortho, meta, para) and the C 2 B 10 skeleton may be stable up to 600 °C. 26 In contrast, icosahedral disilaboranes are only known as air-sensitive 1,2-diphenyl-, 1,2-methylphenyl-, and 1,2-dimethyl- ortho -disilaborane. 27 The latter, (CH 3 ) 2 Si 2 B 10 H 10 , was discovered first.…”

Section: Introductionmentioning

confidence: 99%

Mysterious SiB₃: Identifying the Relation between α- and β-SiB₃

et al. 2019

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Binary silicon boride SiB3 has been reported to occur in two forms, as disordered and nonstoichiometric α-SiB3–x, which relates to the α-rhombohedral phase of boron, and as strictly ordered and stoichiometric β-SiB3. Similar to other boron-rich icosahedral solids, these SiB3 phases represent potentially interesting refractory materials. However, their thermal stability, formation conditions, and thermodynamic relation are poorly understood. Here, we map the formation conditions of α-SiB3–x and β-SiB3 and analyze their relative thermodynamic stabilities. α-SiB3–x is metastable (with respect to β-SiB3 and Si), and its formation is kinetically driven. Pure polycrystalline bulk samples may be obtained within hours when heating stoichiometric mixtures of elemental silicon and boron at temperatures 1200–1300 °C. At the same time, α-SiB3–x decomposes into SiB6 and Si, and optimum time-temperature synthesis conditions represent a trade-off between rates of formation and decomposition. The formation of stable β-SiB3 was observed after prolonged treatment (days to weeks) of elemental mixtures with ratios Si/B = 1:1–1:4 at temperatures 1175–1200 °C. The application of high pressures greatly improves the kinetics of SiB3 formation and allows decoupling of SiB3 formation from decomposition. Quantitative formation of β-SiB3 was seen at 1100 °C for samples pressurized to 5.5–8 GPa. β-SiB3 decomposes peritectoidally at temperatures between 1250 and 1300 °C. The highly ordered nature of β-SiB3 is reflected in its Raman spectrum, which features narrow and distinct lines. In contrast, the Raman spectrum of α-SiB3–x is characterized by broad bands, which show a clear relation to the vibrational modes of isostructural, ordered B6P. The detailed composition and structural properties of disordered α-SiB3–x were ascertained by a combination of single-crystal X-ray diffraction and 29Si magic angle spinning NMR experiments. Notably, the compositions of polycrystalline bulk samples (obtained at T ≤ 1200 °C) and single crystal samples (obtained from Si-rich molten Si–B mixtures at T > 1400 °C) are different, SiB2.93(7) and SiB2.64(2), respectively. The incorporation of Si in the polar position of B12 icosahedra results in highly strained cluster units. This disorder feature was accounted for in the refined crystal structure model by splitting the polar position into three sites. The electron-precise composition of α-SiB3–x is SiB2.5 and corresponds to the incorporation of, on average, two Si atoms in each B12 icosahedron. Accordingly, α-SiB3–x constitutes a mixture of B10Si2 and B11Si clusters. The structural and phase stability of α-SiB3–x were explored using a first-principles cluster expansion. The most stable composition at 0 K is SiB2.5, which however is unstable with respect to the decomposition β-SiB3 + Si. Modeling of the configurational and vibrational entropies suggests that α-SiB3–x only becomes more stable than β-SiB3 at temperatures above its decomposition into SiB6 and Si. Hence, we conclude that α-SiB3–x is metastable at all t...

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