A convenient preparation of 1-CB11H12- and its C-amino derivatives

Plešek, Jaromı́r; Jelı́nek, Tomáš; Drdáková, Eva; Heřmánek, S.; Štı́br, Bohumil

doi:10.1135/cccc19841559

Cited by 122 publications

(118 citation statements)

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“…Carborane anions, [62][63][64] protonated arene salts, 45,58 and H9O4 + salts 27 were prepared as previously described. Solvents were dried by standard methods.…”

Section: Methodsmentioning

confidence: 99%

Molecular Structure of the Solvated Proton in Isolated Salts. Short, Strong, Low Barrier (SSLB) H-bonds

et al. 2002

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Large, inert, weakly basic carborane anions of the icosahedral type CHB11R5X6 - (R = H, Me; X = Cl, Br) allow ready isolation and structural characterization of discrete salts of the solvated proton, [H(solvent) x ][CHB11R5X6], (solvent = common O-atom donor). These oxonium ion Brønsted acids are convenient reagents for the tuned delivery of protons to organic solvents with a specified number of donor solvent molecules and with acidities leveled to those of the chosen donor solvent. They have greater thermal stability than the popular [H(OEt2)2][BArF] acids based on fluorinated tetraphenylborate counterions because carborane anions can sustain much higher levels of acidity. When organic O-atom donors such as diethyl ether, tetrahydrofuran, benzophenone, and nitrobenzene are involved, the coordination number of the proton (x) in [H(solvent) x ]+ is two. A mixed species involving the [H(H2O)(diethyl ether)]+ ion has also been isolated. These solid-state structures provide expectations for the predominant molecular structures of solvated protons in solution and take into account that water is an inevitable impurity in organic solvents. The O···O distances are all short, lying within the range from 2.35 to 2.48 Å. They are consistent with strong, linear O···H···O hydrogen bonding. Density functional theory calculations indicate that all H(solvent)2 + cations have low barriers to movement of the proton within an interval along the O···H···O trajectory, i.e., they are examples of so-called SSLB H-bonds (short, strong, low-barrier). Unusually broadened IR bands, diagnostic of SSLB H-bonds, are observed in these H(solvent)2 + cations.

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“…Carborane anions, [62][63][64] protonated arene salts, 45,58 and H9O4 + salts 27 were prepared as previously described. Solvents were dried by standard methods.…”

Section: Methodsmentioning

confidence: 99%

Molecular Structure of the Solvated Proton in Isolated Salts. Short, Strong, Low Barrier (SSLB) H-bonds

et al. 2002

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“…The IR spectrum shows very little perturbation of the CB 11 cluster bands relative to the silylium starting material so protonation of the anion must occur on the halogen substituents (red atoms X in Fig. 1) at the same positions (7)(8)(9)(10)(11)(12) …”

Section: Synthesis and Characterization Of Carborane Acidsmentioning

confidence: 99%

“…9 The chemistry of CB 11 H 12 2 lay fallow for a couple of decades while research on the neutral and dianionic isolectronic analogues, C 2 B 10 H 12 and B 12 H 12 22 , took precedence. In the mid-1980s, the dedicated Czech boron group of Plešek, Š tibr and Heřmá nek reported an improved synthesis from decaborane 10 and showed that halogenation proceeded quite selectively to give 7,8,9,10,11,12-hexahalogenated anions, CHB 11 H 5 X 6 2 (X 5 Cl, Br; see Fig. 1).…”

Section: Carborane Anionsmentioning

confidence: 99%

Carborane acids. New “strong yet gentle” acids for organic and inorganic chemistry

2005

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Icosahedral carborane anions such as CHB 11 Cl 11 2 are amongst the least coordinating, most chemically inert anions known. They are also amongst the least basic, so their conjugate acids, H(carborane), are superacids (i.e. stronger than 100% H 2 SO 4 ). Acidity scale measurements indicate that H(CHB 11 Cl 11 ) is the strongest pure Brønsted acid presently known, surpassing triflic and fluorosulfuric acid. Nevertheless, it is also an extremely gentle acid-because its conjugate base engages in so little chemistry. Carborane acids separate protic acidity from anion nucleophilicity and destructive oxidative capacity in the conjugate base, to a degree not previously achieved. As a result, many long-sought, highly acidic, reactive cations such as protonated benzene (C 6 H 7 + ), protonated C 60 (HC 60 +), tertiary carbocations (R 3 C + ), vinyl cations (R 2 CLC + -R), silylium ions (R 3 Si + ) and discrete hydronium ions (H 3 O + , H 5 O 2 + etc.) can be readily isolated as carborane salts and characterized at room temperature by X-ray crystallography.

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“…mercapto and dichloro dicarbanonaborates (Na-5-SH 7,8_C2-B9Hll ' Na-5,6-C12-C2-B9H10 ) belong to a new group of dicarbapolyborates synthesized by Plegek et al [13,14]. Dicarbanonaborates were dissolved in water and 1M solutions were stored at 0 ° C. During inhibition studies 2-20ram solutions were employed.…”

Section: Methodsmentioning

confidence: 99%