Dodecamethylcarba-closo-dodecaborate(−) Anion, CB11Me12-

King, Benjamin T.; Janoušek, Zbyněk; Grüner, Bohumı́r; Trammell, Matthew; Noll, Bruce C.; Michl, Josef

doi:10.1021/ja9541443

Cited by 137 publications

(177 citation statements)

References 20 publications

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“…Permethylation of the icosahedral CB 11 H 12 -carborane to give CB 11 Me 12 -increases solubility dramatically, but at the cost of inertness. 16 Trifluoromethyl groups can lead to explosive decomposition. 17 We now show that mixed halogen and methyl substituents provide the golden mean.…”

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confidence: 99%

“…Polarity of the CB 11 cage directs halogenation of the icosahedral parent carborane, 1-H-CB 11 H 11 -, first to the 12-position (antipodal to carbon) and then to the 7-11 positions of the "lower" pentagonal belt. 18,19 Treatment of the 7,8,9,10,11,12-hexahalo derivatives, 1-H-CB 11 H 5 X 6 -(X ) Cl, Br, I), with methyl triflate under conditions of elevated temperature and triflic acid catalysis 16 leads cleanly to 2-5 pentamethylation (>80% yields). 20 The unique C-H bond is untouched by these conditions.…”

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confidence: 99%

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Optimizing the Least Nucleophilic Anion. A New, Strong Methyl⁺ Reagent

2002

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The icosahedral carborane anions H-CB11X6H5 - (X = Cl, Br, I) are among the most inert, least coordinating, and least basic anions known. These properties are enhanced by 2,3,4,5,6-pentamethylation with methyl triflate. The resulting anions, H-CB11X6Me5 -, are more inert than their unmethylated precursors, have improved NMR handles, and their salts have higher solubility in low dielectric media. They sustain superacidity in H(H-CB11X6Me5). Protonated benzene has been isolated and characterized by X-ray crystallography, moving Wheland intermediates from the status of spectroscopically observable transients to weighable reagents. The new anions sustain extreme Lewis acidity in silylium ion-like R3Si(H-CB11X6Me5) species. Treatment of Et3Si(H-CB11Br6Me5) with methyl triflate leads to a new methyl+ reagent CH3(H-CB11Br6Me5) that is more potent than methyl triflate. It methylates benzene without heating or acid catalysis to give the toluenium ion. The H-CB11X6Me5 - anions come as close as any to the concept of a univeral weakly coordinating anion and, with cheaper starting materials now available, promise to become specialty chemicals of wide usage.

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Optimizing the Least Nucleophilic Anion. A New, Strong Methyl⁺ Reagent

2002

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“…À , [11] and closo-1,12-C 2 B 10 (CH 3 ) 12 , [12] have been synthesized. Similar highly substituted polyhedral borane derivatives with hydrophilic substituents such as hydroxyl are, until now, unknown.…”

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confidence: 99%

Aromatic Polyhedral Hydroxyborates: Bridging Boron Oxides and Boron Hydrides

Peymann

Herzog

Knobler

et al. 1999

Angew. Chem. Int. Ed.

116

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“…The ylide 3 has been prepared from the 12-cyanomonocarba-closo-dodecaborate anion 12-CNCB 11 H 11 − (2) 6,7 by reaction with trimethyloxonium tetrafluoroborate in nitromethane or by treatment with methyl triflate in sulfolane under conditions ordinarily used for methylation of the BH vertices of 1 17 (Scheme 1). The Scheme 1.…”

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confidence: 99%