The B<sup>11</sup> Nuclear Magnetic Resonance Chemical Shifts and Spin Coupling Values for Various Compounds

Onak, Thomas; Landesman, Herbert; Williams, Robert L.; Shapiro, I.

doi:10.1021/j150579a601

Cited by 254 publications

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“…11 B-NMR chemical shifts were calculated relative to B 2 H 6 and converted into the usual BF 3 ·OEt 2 scale by using the experimental value of B 2 H 6 of 16.6 ppm. [52] Search Parameters for Cambridge Structural Database: Search procedures in Cambridge Structural Database (CSD) were done using ConQuest.…”

Section: Methodsmentioning

confidence: 99%

The Role of C–H···H–B Interactions in Establishing Rotamer Configurations in Metallabis(dicarbollide) Systems

et al. 2010

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The aim of this work is to explore the self-interaction capability of the anion [3,3Ј-Co(1,2-C 2 B 9 H 11 ) 2 ] -through C cluster -H···H-B (C c -H···H-B) dihydrogen bonds. A set of theoretical and empirical data aiming to establish the main rules that account for the binding mode between the negatively charged borane framework made by [3,3Ј-Co(1,2-C 2 B 9 H 11 ) 2 ] -and the [NMe 4 ] + ions have been compiled. The interaction between cation and anion is mainly electrostatic but the covalent contribution is also proven and quantified. The exi-

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Section: Methodsmentioning

confidence: 99%

The Role of C–H···H–B Interactions in Establishing Rotamer Configurations in Metallabis(dicarbollide) Systems

et al. 2010

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“…The peak at m/z 403.4 (maximum intensity) corresponds to the dimeric form of the ligand [1-CH 3 -2-CO 2 H-1,2-closo-C 2 B 10 H 10 ] 2 in which two ligand units form two hydrogen bonds between themselves (calculated energy 7 kJmol À1 bond) as it has been reported. [26] The peak found at m/z 157 (70.3 %) corresponds to 1-CH 3 -1,2-C 2 B 10 H 11 . The weak intensity ionic peaks at 201.1 and 191.1 correspond, respectively, to the free ligand, [1-CH 3 -2-CO 2 -1,2-closo- The higher-energy transition can be assigned to LMCT bands from p orbitals of the carboxylato ligands to the empty d x 2 Ày 2 orbitals of the Cu II cations.…”

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confidence: 97%

“…According to the literature, [23] the chemical shift for BA C H T U N G T R E N N U N G (OCH 3 ) 3 appears at d = + + 17.2, [24] 17.6, [25] or 18.1 ppm. [26] Having determined the fate of the extracted BH 2 + , we turned to the question of how the BA C H T U N G T R E N N U N G (OCH 3 ) 3 was formed. Our explanation on why the partial degradation reaction of the 1-CH 3 -2-CO 2 H-1,2-closo-C 2 B 10 H 10 ligand takes place is based on the fact that, once the complex is dissolved in CH 3 OH, there is free p-CF 3 -py ligand in the solution in methanol.…”

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confidence: 99%

Design of Dinuclear Copper Species with Carboranylcarboxylate Ligands: Study of Their Steric and Electronic Effects

Fontanet

Popescu

Fontrodona

et al. 2011

Chemistry A European J

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A series of new mononuclear and carboranylcarboxylate-bridged dinuclear copper(II) compounds containing the 1-CH(3)-2-CO(2)H-1,2-closo-C(2)B(10)H(10) carborane ligand (LH) has been synthesized. Reaction of different copper salts with LH at room temperature leads to dinuclear compounds of the general formula [Cu(2)(μ-L)(4)(L(t))(2)] (L(t) = thf (1), L(t) = H(2)O (1')). The reaction of 1 and 1' with different terminal pyridyl (py) ligands leads to the formation of a series of structurally analogous complexes by substitution of the terminal ligand thf or H(2)O (L(t) = py (2), p-CF(3)-py (3), p-CH(3)-py (4), pz (6), and 4,4'-bpy (7)), which maintain the structural Cu(2)(μ-O(2)CR)(4) core in the majority of the cases except for o-(CH(3))(2)-py, where a mononuclear compound (5) is exclusively obtained. These compounds have been characterized through analytical, spectroscopic (NMR, IR, UV-visible, ESI-MS) and magnetic techniques. X-ray structural analysis revealed a paddle-wheel structure for the dinuclear compounds, with a square-pyramidal geometry around each copper ion and the carboranylcarboxylate ions bridging two copper atoms in syn-syn mode. The mononuclear complex obtained with the o-(CH(3))(2)-py ligand presents a square-planar structure, in which the carboranylcarboxylate ligand adopts a monodentate coordination mode. The magnetic properties of the dinuclear compounds 1, 3, 4, and 6 show a strong antiferromagnetic coupling in all cases (J = -261 (1), -255 (3), -241 (4), -249 cm(-1) (6)). Computational studies based on hybrid density functional methods have been used to study the magnetic properties of the complexes and also to evaluate their relative stability on the basis of the strength of the bond between each Cu(II) and the terminal ligand.

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“…The 11 B resonances were calibrated using 1 M NaBH 4 as an external reference at −38.7 ppm. 15 Two cells were charged at a constant current of 0.500 A until reaching a voltage of 5.35 V; both cells were then held at this voltage for 1 h. One cell was discharged at constant current of 0.500 A, held at 3.0 V, and was then disassembled inside an Ar glove box. Half of the cathode material from each cell was subject to a rinsing procedure in which the substances were subject to three separate 10 min soaks in previously dried dimethyl carbonate ͑DMC͒.…”

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Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

West

Whitacre

Leifer

et al. 2007

J. Electrochem. Soc.

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We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and 11 B nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties. As cathodes in lithium batteries, carbon-fluoride ͑C-F͒ compounds offer very high theoretical specific capacity, on the scale of 1785 mAh/g for C 1.25 F, though to date, all C-F compounds regardless of preparation conditions are strictly non-rechargeable. A rechargeable C-F cathode would be very desirable in terms of specific energy relative to conventional lithium-ion transition metal oxide cathodes, though there are numerous difficulties associated with reversible fluorination of carbon which relate to a large extent to the nature of the C-F bond.The reaction of carbon and fluorine is well known to yield a wide range of useful compounds with varying properties, depending on preparation conditions and synthesis route. Many of these compounds, despite their relatively poor electronic conductivity, are useful as cathodes for primary Li batteries. Direct reaction of fluorine gas with graphite at temperatures greater than 350°C results in covalent bonding of C x -F with the transition of the planar sp 2 graphene sheets to buckled sp 3 carbon, and concomitant drop in electrical conductivity with decreasing x. Room temperature chemical fluorination of graphite in the presence of various fluorides such as HF, WF 6 , SbF 5 , and IF 5 has been demonstrated by others up to C 1.0 F 0.89 ͑I 0.02 H 0.06 ͒. 1 Under these preparation conditions, the sp 2 carbon hybridization is maintained, and the C-F bonding is ionic. Electrochemical fluorination of graphite in aqueous or anhydrous HF media is also possible, resulting in ionic or semi-covalent C x -F depending on the degree of fluorination, though this process is not significantly reversible and has poor Coulombic efficiency. 2-4 A candidate rechargeable C-F cathode must retain good electronic conductivity and thus the practical lower bound on C x F is likely near the C-F delocalizati...

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The B¹¹ Nuclear Magnetic Resonance Chemical Shifts and Spin Coupling Values for Various Compounds

Cited by 254 publications

References 0 publications

The Role of C–H···H–B Interactions in Establishing Rotamer Configurations in Metallabis(dicarbollide) Systems

The Role of C–H···H–B Interactions in Establishing Rotamer Configurations in Metallabis(dicarbollide) Systems

Design of Dinuclear Copper Species with Carboranylcarboxylate Ligands: Study of Their Steric and Electronic Effects

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

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The B11 Nuclear Magnetic Resonance Chemical Shifts and Spin Coupling Values for Various Compounds

Cited by 254 publications

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The Role of C–H···H–B Interactions in Establishing Rotamer Configurations in Metallabis(dicarbollide) Systems

The Role of C–H···H–B Interactions in Establishing Rotamer Configurations in Metallabis(dicarbollide) Systems

Design of Dinuclear Copper Species with Carboranylcarboxylate Ligands: Study of Their Steric and Electronic Effects

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

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The B¹¹ Nuclear Magnetic Resonance Chemical Shifts and Spin Coupling Values for Various Compounds