A Perfluorinated Nanosphere: Synthesis and Structure of Perfluoro-deca-B-methyl-para-carborane

Herzog, A.; Callahan, Ryan P.; Macdonald, Charles L. B.; Lynch, Vincent M.; Hawthorne, M. Frederick; Lagow, Richard J.

doi:10.1002/1521-3773(20010601)40:11<2121::aid-anie2121>3.0.co;2-d

Cited by 31 publications

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“…closo -Carboranes containing CF 3 groups instead of fluorine substituents are less stable, probably due to a loss of stabilization through π-back-donation. The extreme example [CB 11 (CF 3 ) 12 ] - tends to explode, whereas other trifluoromethylcarboranes, e.g., (CF) 2 B 10 (CF 3 ) 10 , exhibit higher stability . The decomposition is probably initiated by a fluoride ion abstraction from a CF 3 group followed by opening of the cluster at the electron deficient C atom, similar to reactions described for the N atom in MeNB 11 H 11 .…”

Section: Resultsmentioning

confidence: 75%

“…The extreme example [CB 11 (CF 3 ) 12 ]tends to explode, 59 whereas other trifluoromethylcarboranes, e.g., (CF) 2 B 10 (CF 3 ) 10 , exhibit higher stability. 60 The decomposition is probably initiated by a fluoride ion abstraction from a CF 3 group followed by opening of the cluster at the electron deficient C atom, similar to reactions described for the N atom in MeNB 11 H 11 . 61 The resulting strong Lewis acid can attack one of the remaining CF 3 groups, and the decomposition can proceed.…”

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confidence: 78%

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Rearrangement Reactions of the Transient Lewis Acids (CF₃)₃B and (CF₃)₃BCF₂: An Experimental and Theoretical Study

et al. 2003

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Short-lived (CF(3))(3)B and (CF(3))(3)BCF(2) are generated as intermediates by thermal dissociation of (CF(3))(3)BCO and F(-) abstraction from the weak coordinating anion [B(CF(3))(4)](-), respectively. Both Lewis acids cannot be detected because of their instability with respect to rearrangement reactions at the B-C-F moiety. A cascade of 1,2-fluorine shifts to boron followed by perfluoroalkyl group migrations and also difluorocarbene transfer reactions occur. In the gas phase, (CF(3))(3)B rearranges to a mixture of linear perfluoroalkyldifluoroboranes C(n)()F(2)(n)()(+1)BF(2) (n = 2-7), while the respective reactions of (CF(3))(3)BCF(2) result in a mixture of linear (n = 2-4) and branched monoperfluoroalkyldifluoroboranes, e.g., (C(2)F(5))(CF(3))FCBF(2). For comparison, the reactions of [CF(3)BF(3)](-) and [C(2)F(5)BF(3)](-) with AsF(5) are studied, and the products in the case of [CF(3)BF(3)](-) are BF(3) and C(2)F(5)BF(2) whereas in the case of [C(2)F(5)BF(3)](-), C(2)F(5)BF(2) is the sole product. In contrast to reports in the literature, it is found that CF(3)BF(2) is too unstable at room temperature to be detected. The decomposition of (CF(3))(3)BCO in anhydrous HF leads to a mixture of the new conjugate Brønsted-Lewis acids [H(2)F][(CF(3))(3)BF] and [H(2)F][C(2)F(5)BF(3)]. All reactions are modeled by density functional calculations. The energy barriers of the transition states are low in agreement with the experimental results that (CF(3))(3)B and (CF(3))(3)BCF(2) are short-lived intermediates. Since CF(2) complexes are key intermediates in the rearrangement reactions of (CF(3))(3)B and (CF(3))(3)BCF(2), CF(2) affinities of some perfluoroalkylfluoroboranes are presented. CF(2) affinities are compared to CO and F(-) affinities of selected boranes showing a trend in Lewis acidity, and its influence on the stability of the complexes is discussed. Fluoride ion affinities are calculated for a variety of different fluoroboranes, including perfluorocarboranes, and compared to those of the title compounds.

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Section: Resultsmentioning

confidence: 75%

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confidence: 78%

Rearrangement Reactions of the Transient Lewis Acids (CF₃)₃B and (CF₃)₃BCF₂: An Experimental and Theoretical Study

et al. 2003

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“…The perfluorination of the much cheaper [B 12 H 12 ] 2- dianion to [B 12 F 12 ] 2- has been reported and improved − repeatedly, but the presently unknown anodic oxidation potential of the latter is most likely less positive than that of [1-H−CB 11 F 11 ] − ( 1 ). Trifluoromethylated uncharged carboranes are also known …”

Section: Introductionmentioning

confidence: 99%

HCB₁₁(CF₃)_nF_11-n⁻: Inert Anions with High Anodic Oxidation Potentials

2011

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Cs salts of four of the title anions were prepared by fluorination of salts of partly methylated (n = 11, 10) or partly methylated and partly iodinated (n = 6, 5) CB(11)H(12)(-) anions. The CH vertex is acidic, and in the unhindered anion with n = 6 it has been alkylated. Neat Cs(+)[1-H-CB(11)(CF(3))(11)](-) is as treacherously explosive as Cs(+)[CB(11)(CF(3))(12)](-), but no explosions occurred with the salts of the other three anions. BL3YP/6-31G* gas-phase electron detachment energies of the title anions are remarkably high, 5-8 eV. Treated with NiF(3)(+) in anhydrous liquid HF at -60 °C, anions with n = 11 or 10 resist oxidation, whereas anions with n = 6 or 5 are converted to colored EPR-active species, presumably the neutral radicals [HCB(11)(CF(3))(n)F(11-n)](•). These are stable for hours at -60 °C after extraction into cold perfluorohexane or perfluorotri-n-butylamine solutions. On warming to -20 °C in a Teflon or quartz tube, the color and EPR activity disappear, and the original anions are recovered nearly quantitatively, suggesting that the radicals oxidize the solvent.

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“…The high symmetry of the 12-vertex B 12 H 12 2- icosahedron has always attracted attention from an aesthetic standpoint − may change to more practical applications since the discovery that all 12 positions can be functionalized. − Some of the 12-vertex cages are known to exist with less than the closo number of cage-bonding electrons (2 n + 2, where n = number of vertexes), in particular hypercloso species such as B 12 Cl 12 . The usual explanation for their stability is that the exo halide substituent supplies additional electron density to the cage through π donation.…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theory Study of Anionic and Neutral Per-Substituted 12-Vertex Boron Cage Systems, B₁₂X₁₂ⁿ^- (n = 2, 1, 0)

McKee

2002

Inorg. Chem.

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The 12(12) closomers form a rapidly expanding class of compounds where a 12-vertex cage is surrounded by 12 identical substituents. Density functional theory (B3LYP/6-31G(d)) is used to study a number of these closomers in different states of oxidation (dianion, radical anion, and neutral cages). The cage stability increases as the group electronegativity of the substituent increases. Also, the 12(12) closomer becomes easier to oxidize as the Hammett sigma(p) parameter becomes more negative (electron-donating). As the closomer is oxidized, the size of the cage increases and the B-B distances become more asymmetric. The Raman-active breathing mode in the 404-434 cm(-1) range moves to lower frequency as the cage is oxidized, which is caused by removing one or two electrons from a cage-bonding molecular orbital.

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A Perfluorinated Nanosphere: Synthesis and Structure of Perfluoro-deca-B-methyl-para-carborane

Abstract: Science Foundation (USA) (NSF CHE 9314037) and (NSF CHE 9972888). We gratefully thank graduate student Theodore W. Bitner and Prof. Jeffrey I. Zink, UCLA, for the acquisition of the Raman spectra.

Cited by 31 publications

References 26 publications

Rearrangement Reactions of the Transient Lewis Acids (CF₃)₃B and (CF₃)₃BCF₂: An Experimental and Theoretical Study

Rearrangement Reactions of the Transient Lewis Acids (CF₃)₃B and (CF₃)₃BCF₂: An Experimental and Theoretical Study

HCB₁₁(CF₃)_nF_11-n⁻: Inert Anions with High Anodic Oxidation Potentials

Density Functional Theory Study of Anionic and Neutral Per-Substituted 12-Vertex Boron Cage Systems, B₁₂X₁₂ⁿ^- (n = 2, 1, 0)

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A Perfluorinated Nanosphere: Synthesis and Structure of Perfluoro-deca-B-methyl-para-carborane

Abstract: Science Foundation (USA) (NSF CHE 9314037) and (NSF CHE 9972888). We gratefully thank graduate student Theodore W. Bitner and Prof. Jeffrey I. Zink, UCLA, for the acquisition of the Raman spectra.

Cited by 31 publications

References 26 publications

Rearrangement Reactions of the Transient Lewis Acids (CF3)3B and (CF3)3BCF2: An Experimental and Theoretical Study

Rearrangement Reactions of the Transient Lewis Acids (CF3)3B and (CF3)3BCF2: An Experimental and Theoretical Study

HCB11(CF3)nF11-n−: Inert Anions with High Anodic Oxidation Potentials

Density Functional Theory Study of Anionic and Neutral Per-Substituted 12-Vertex Boron Cage Systems, B12X12n- (n = 2, 1, 0)

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Rearrangement Reactions of the Transient Lewis Acids (CF₃)₃B and (CF₃)₃BCF₂: An Experimental and Theoretical Study

Rearrangement Reactions of the Transient Lewis Acids (CF₃)₃B and (CF₃)₃BCF₂: An Experimental and Theoretical Study

HCB₁₁(CF₃)_nF_11-n⁻: Inert Anions with High Anodic Oxidation Potentials

Density Functional Theory Study of Anionic and Neutral Per-Substituted 12-Vertex Boron Cage Systems, B₁₂X₁₂ⁿ^- (n = 2, 1, 0)