Boron-11, boron-10, and nitrogen-14 NMR relaxation rates and quadrupole coupling constants in BH<sub>3</sub>NH<sub>3</sub>

Penner, Glenn H.; Daleman, Stephen I.; Custodio, Angela R.

doi:10.1139/v92-307

Cited by 11 publications

(5 citation statements)

References 30 publications

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“…Although the x values are not quantitatively reproduced, the trend of decreasing x with decreasing size of the E-atom is apparant. It has been shown that x values calculated with large basis sets (e.g., 6-3 lG*) and at levels where second-order correlation effects are taken into account (e.g., MP2 or CI) are in good aggreement with those obtained from gas phase experiments (e.g., microwave spectroscopy) (25)(26)(27). The large size of the S e and T e atoms has restricted our calculations to the STO-3G* basis; therefore electron correlation effects are not taken into account.…”

Section: Variation Of Y In the Series (Ch)e+mentioning

confidence: 93%

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH₃)₃E⁺X⁻ and C₆H₅M(CH₃)₃⁺I⁻

Penner¹,

Polson²,

Daleman³

et al. 1993

Can. J. Chem.

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Deuterium NMR measurements are reported for two types of onium salts: (CH,),E+I-, where E = 0 (counterion is BF,-), S, Se, or Te, and C6HSM(CH3),+I-, where M = N, P, or As. Within each class of compounds the activation energy for rotation of the trimethyl groups about the C; axis increases with increasing size of the central atom. In the first class of compounds the C-E-C bond angle decreases with the size of the atom E. In addition the magnitude of the quadrupolar coupling constant, X , varies with E, ranging from 160 kHz for E = 0 to 190 kHz for E = Te. This is in qualitative agreement with molecular orbital calculations of the electric field gradients. At low temperatures the ' H NMR spectrum of C,H5N(CH3),+I-can only be rationalized with a model in which trimethyl rotation is faster than methyl rotation. The %I NMR of ring (predominantly ortho and para)-deuterated C6H5N(CH,),+I is consistent with rapid rz-site (rz 2 3) rotation of the phenyl ring above 390 K. Below 390 K spectra characteristic of two-site, 18O0, flips of the phenyl ring are observed. Below 280 K the motion of the phenyl ring is in the rigid lattice limit. Chem. 71,417 (1993). On a effectuk des mesures de RMN du deuterium pour deux types de sels onium : (CH3)3E+I-dans lesquels E = 0 (le contre-ion est le BFJ, S, Se ou Te, et C,H5M(CH3), dans lesquels M = N, P ou As. Dans chacune de ces classes de composes, I'energie d'activation de la rotation des groupes mkthyles autour de l'axe C; augmente avec une augmentation de la taille de I'atome central. Dans la premiere classe de composes, l'angle de la llaison C-E-C augmente avec une augmentation de la taille de l'atome E. De plus, l'amplitude de la constante de couplage quadripolaire, X, varie avec E; elle varie de 160 kHz pour E = 0 a 190 kHz pour E Te. Ce resultat est en accord qualitatif avec les calculs d'orbitales molkculaires des gradients des champs klectriques. A basses tem$ratures, on ne peut rationaliser les spectres RMN du ' H du C6HSN(CH3)3fI-qu'a I'aide d'un modele dans lequel la rotation de trimethyle est plus rapide que celle du methyle. Le spectre RMN du %I du cycle C,H5N(CH3),+1-deutCrC (principalement en ortho et para) est en accord avec la rotation rapide de n-sites (rz 2 3) du cycle phknyle B des temperatures supkrieures a 390 K. A des tempkratures inferieures B 390 K, on observe des spectres caractkristiques de rotations rapides des noyaux phknyles sur deux sites, 180". En-dessous de 280 K, les dkplacements du noyau phenyle se font dans les limites d'un reseau rigide.[Traduit par la redaction]

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Section: Variation Of Y In the Series (Ch)e+mentioning

confidence: 93%

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH₃)₃E⁺X⁻ and C₆H₅M(CH₃)₃⁺I⁻

Penner¹,

Polson²,

Daleman³

et al. 1993

Can. J. Chem.

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“…Figure 6. Temperature dependence of the boron NMR spectra of (9) in the presence of pyridine-d5 (0.5 eqv.) acquired by using 11 B single pulse (left), 11 B-DEPTH (middle) and 10…”

Section: Bmentioning

confidence: 99%

“…Indeed, 10 B NMR applications are limited to special cases, e.g. measurement of J ‐couplings, mechanistic investigations based on 10 B labelling, relaxation studies, boron neutron capture therapy of cancer and the solid‐state NMR of boron doped diamond.…”

Section: Introductionmentioning

confidence: 99%

Background‐free solution boron NMR spectroscopy

Király

2012

Magnetic Reson in Chemistry

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The appearance of background signals arising from the NMR probe and tube is a well-known problem of boron NMR spectroscopy. Background suppression may be achieved by using DEPTH, which increases the signal-to-background (S/B) ratio. Although, the quality of such spectra is often adequate, but in the case of rapid relaxation broadened resonances (T(1) < 1 ms), the residual background signals may still hamper the interpretation of the spectra. It was observed that the background signals are practically invisible in solution (10) B NMR. The unusual isotopic effect on the (S/B) ratio was interpreted as an inherent consequence of the integer versus half-integer spin of (10) B and (11) B, respectively. The practicability of (10/11) B NMR was compared for a selected set of boron compounds covering the typical range of (S/B) ratio. The application of (11) B is more favourable than (10) B as long as it is possible to achieve the desired spectral quality by using DEPTH. Otherwise, the 'background-free' appearance of (10) B NMR spectra makes (10) B a reasonable alternative of (11) B DEPTH. This was found typical for compounds having relaxation broadened resonances. The variable temperature (VT) NMR study of an adduct formation process was also presented here as an example of the advantage of (10) B over (11) B.

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“…In solution, the dipole moment has been measured and the vibrational modes have been assigned . The 11 B, 14 N, 15 N, and 1 H chemical shifts and spin−spin coupling constants have been measured in a number of solvents. − The 11 B, 10 B, and 14 N spin−lattice relaxation times ( T 1 ) have been measured in aqueous solution and related to the nuclear QCCs as obtained by microwave spectroscopy, nuclear quadrupolar resonance (NQR) spectroscopy, and ab initio molecular orbital theory …”

Section: Introductionmentioning

confidence: 99%

A Deuterium NMR Spectroscopic Study of Solid BH₃NH₃

1999

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Deuterium nuclear magnetic resonance (NMR) powder spectra and spin-lattice relaxation times (T(1)) are used to measure the deuterium quadrupolar coupling constants (QCCs) chi(BD) and chi(ND) and to investigate the molecular reorientation of the BD(3) and ND(3) groups in solid deuterated borane monoammoniate, BD(3)NH(3) and BH(3)ND(3), respectively. In the high-temperature, tetragonal, phase (above 225 K) the following Arrhenius parameters are obtained from the temperature-dependent T(1): E(a) = 5.9 +/- 0.5 kJ/mol and tau(infinity) = 1.1 x 10(-)(13) s for BD(3)NH(3); E(a) = 7.3 +/- 0.8 kJ/mol and tau(infinity) = 4.4 x 10(-)(14) s for BH(3)ND(3). In the low-temperature, orthorhombic, phase the following parameters are obtained: E(a) = 26.4 +/- 1.4 kJ/mol and tau(infinity) = 1.2 x 10(-)(17) s for BD(3)NH(3); E(a) = 13.7 +/- 0.9 kJ/mol and tau(infinity) = 5.7 x 10(-)(15) s for BH(3)ND(3). Here tau(infinity) is proportional to the inverse of the usual Arrhenius preexponential factor, A. Deuterium line shape measurements for the low-temperature phase of BD(3)NH(3) yield E(a) = 25 +/- 2 kJ/mol and tau(infinity) = 4.7 x 10(-)(19) s. These dynamic factors indicate that the molecule is probably undergoing whole molecule rotation above the phase transition but the BH(3) and NH(3) groups are undergoing uncorrelated motion in the low-temperature phase. Deuterium quadrupolar coupling constants of 105 +/- 10 and 200 +/- 10 kHz were determined for BD(3)NH(3) and BH(3)ND(3), respectively. Molecular orbital (MO) calculations (CI(SD)/6-31G(d,p)//MP2/6-31G(d,p)) for the isolated molecule yield values of 143 and 255 kHz. MO calculations also show that the deuterium quadrupolar coupling constants chi(BD) and chi(ND) are relatively insensitive to all molecular structural parameters except the B-H and N-H bond lengths, respectively. It is suggested that the large decrease in the QCC on going from the gas phase to the solid state may be due to a slight lengthening of the B-H and N-H bonds, possibly a result of attractive B-H.H-N interactions.

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Boron-11, boron-10, and nitrogen-14 NMR relaxation rates and quadrupole coupling constants in BH₃NH₃

Cited by 11 publications

References 30 publications

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH₃)₃E⁺X⁻ and C₆H₅M(CH₃)₃⁺I⁻

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH₃)₃E⁺X⁻ and C₆H₅M(CH₃)₃⁺I⁻

Background‐free solution boron NMR spectroscopy

A Deuterium NMR Spectroscopic Study of Solid BH₃NH₃

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Boron-11, boron-10, and nitrogen-14 NMR relaxation rates and quadrupole coupling constants in BH3NH3

Cited by 11 publications

References 30 publications

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH3)3E+X− and C6H5M(CH3)3+I−

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH3)3E+X− and C6H5M(CH3)3+I−

Background‐free solution boron NMR spectroscopy

A Deuterium NMR Spectroscopic Study of Solid BH3NH3

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Product

Resources

About

Boron-11, boron-10, and nitrogen-14 NMR relaxation rates and quadrupole coupling constants in BH₃NH₃

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH₃)₃E⁺X⁻ and C₆H₅M(CH₃)₃⁺I⁻

A deuterium NMR study of molecular dynamics and geometry in two classes of onium salts: (CH₃)₃E⁺X⁻ and C₆H₅M(CH₃)₃⁺I⁻

A Deuterium NMR Spectroscopic Study of Solid BH₃NH₃