J. D. Odom

Mercury-199 fourier transform nuclear magnetic resonance spectroscopy

Abstract A general study of mercury-199 Fourier transform nuclear magnetic resonance has been completed. In sensitivity studies 25 millimolar solutions of isotopically normal mercury in HgCl2 exhibited a resonance with a root-mean-square signal-to-noise ratio of 9.1 in 10.2 hours. Mercury-199 chemical shifts of several mercury-containing pesticides are reported. A discussion of possible candidates for 199Hg chemical shift references is presented. Measurements of the 199Hg chemical shift of dimethylmercury in twenty solvents and diethylmercury in several of the same solvents demonstrate a very large solvent influence on these chemical shifts. The spin-lattice relaxation times (T1 values) of 199Hg in neat dimethyl- and divinylmercury are 0.87 and 0.25 sec, respectively. The temperature dependences of the T1 values and the nuclear Overhauser enhancements indicate that the predominant relaxation mechanisms in these two compounds are chemical shift anisotropy and spin rotation, but the data does not allow detailed interpretation in terms of these mechanisms.

Nuclear magnetic resonance studies of boron compounds : XVI. Carbon-13 studies of organoboranes: Phenylboranes and boron-substituted aromatic heterocycles☆

Abstract 13C and 11B NMR data of 29 phenylboranes and 9 boron-substituted aromatic heterocycles (thiophene, N-methylpyrrole and furan) are discussed. The observed 13C chemical shifts of the para-carbon atoms in phenylboranes and the corresponding carbon atoms in the aromatic heterocycles are consistent with mesomeric interactions of the boryl group with the aromatic system. The trend of δ(13C(para)) in phenylboranes corresponds to that observed for isoelectronic phenylcarbocations. Low temperature 13C NMR and/or 13C {11B, 1H} heterocuclear triple resonance experiments were employed to obtain the 13C chemical shifts of the boron-bonded carbon atoms.

Spectra and structure of gallium compounds. II. Microwave, infrared, and Raman spectra, structure, and vibrational assignment of trimethylaminegallane

The microwave spectra of (CH3)3 14N 69GaH3, (CH3)3 14N 71GaH3, (CH3)3 15N 69GaH3, (CH3)3 15N 71GaH3, (CH3)3 14N 69GaD3 and (CH3)3 14N 71GaD3 were recorded from 26.5 to 40.0 GHz resulting in the first gas phase structural determination for a gallane adduct. An rs distance of 2.111±0.002 A was obtained for the Ga–N bond. With reasonable assumptions for the structural parameters for the methyl moiety and the Ga–H distance the following molecular parameters were determined: r(N–C)=1.47 A, uGaNC=110.0°, and uNGaH=102.0°. The barrier to internal rotation of the GaD3 moiety was calculated from the relative intensity of the vibrational satellites to be 1.2 kcal/mole. The infrared (200–4000 cm−1) and Raman spectra (50–3500 cm−1) of (CH3)3 NGaH3, (CH3)3 NGaD3, and (CH3)3 15NGaH3 have been recorded for the solid state at low temperature. The spectra have been interpreted in detail on the basis of C3v molecular symmetry. The splitting of the degenerate E modes in the spectra of the solids indicates that the previousl...

The chemistry of trivalent uranium: The synthesis and reaction chemistry of the tetrahydrofuran adduct of uranium trichloride, UCl3(THF)x☆

Abstract Uranium tetrachloride in THF solution has been found to react with NaH to yield UCl3(THF)x. From this solution the 1:1 adduct UCl3(THF) has been isolated. Unlike the parent UCl3, this material is soluble in THF enabling the study of a variety of reactions. The reactions of UCl3(THF)x with 4-picoline-N-oxide, TICp, NaCp and NaBH4 have been studied as well as the decomposition of UCl3(THF) at elevated temperatures.

77Se NMR on an XL-100 spectrometer. An investigation of isotope effects and spin-lattice relaxation in H2Se

Abstract The design of a voltage-controlled oscillator (VCO), phase-locked to the 1-MHz output of a commercial frequency synthesizer (General Radio 1061), is described. The output frequency of the VCO, capable of producing either 15.400000 or 15.300000 MHz, has been injected into the lock channel of a Varian XL-100 spectrometer as the deuterium field/frequency lock transmitter frequency. This modification allows “normal” proton-decoupled 77Se FT NMR spectra to be obtained on this spectrometer. Secondary deuterium-induced isotope shifts of more than 7 ppm have been observed in the 77Se NMR spectrum of a solution of H2−nDnSe (n = 0, 1, and 2) in deuteriochloroform. Primary and secondary isotope effects on the 77Se-1H coupling constants are also observed. Also, it is shown that 77Se spin-lattice relaxation in hydrogen selenide is dominated completely by the spin-rotation mechanism.

Synthesis of (4S,5R)-(–)-4-methyl-5-phenyloxazolidine-2-selone: a chiral auxiliary reagent capable of detecting the enantiomers of (R,S)-lipoic acid by 77Se nuclear magnetic resonance spectroscopy

(4S,5R)-(–)-4-Methyl-5-phenyloxazolidine-2-selone was constructed in 5 steps on the 10-gram scale. 77Se NMR spectroscropic studies revealed that this selone served as a remarkably sensitive chiral auxiliary agent which readily distinguished the selone-coupled (R,S)-lipoic acid (Δδ 0.119 ppm), even though its chiral centre was separated by 8 bonds from the observed nucleus.

Spectra and structure of phosphorus-boron compounds: Part XXII. Infrared and Raman spectra, vibrational assignment and conformational analysis for ethylphosphine-borane

Abstract The infrared (3200-50 cm−1) and Raman (3200-10 cm−1) spectra of CH3CH2PH2BH3, CH3CH2PD2BH3, CH3CH2PH2BD3 and CH3CH2PD2BD3 in the solid phase at 77 K have been recorded. Additionally, the mid-IR spectra of the gaseous phase and the Raman spectra and polarization of the liquid phase at room temperature have been recorded. Both gauche and trans rotational isomers have been observed in the fluid states and the spectra have been interpreted on the basis of Cs molecular symmetry for the more stable trans conformer. Values of ΔH and ΔS for the conformational equilibrium in the liquid phase have been calculated to be 586 cal mol−1 and 3.6 eu, respectively. A vibrational assignment of the 36 normal modes of the four isotopic species of ethylphosphine-borane has been made based on IR band contours, Raman depolarization values and group frequencies. These results are compared to similar quantities for some corresponding molecules.

Studies in selenium-77 and tellurium-125 nuclear magnetic resonance. Substituent effects and polarizability

Abstract Selenium-77 substituent-caused chemical shifts, where the substituents are alkyl groups, have been studied for a series of selenols, selenides and diselenides, respectively. An understanding of the origin of these shifts was obtained by examining solvent effects on 77 Se chemical shifts of dialkyl selenides and dialkyl diselenides in ten halocarbon solvents of varying molecular polarizabilities as well as in 2,2,2-trifluoroethanol. Based on these results of intermolecular polarizability, an intramolecular polarizability concept is proposed whereby dispersion forces within a molecule exerted by neighboring alkyl and haloalkyl groups influence selenium shielding. This effect along with the well-known “γ effect” offer a clear understanding of a large number of 77 Se chemical shifts. The same intramolecular polarizability concept can be used when examining the chemical shifts of tellurides and ditellurides. Here, even larger substituent caused chemical shifts are observed. Solvent effects on 125 Te chemical shifts of dimethyl telluride were also examined in solvents of varying polarizability. As in the case of several selenides and diselenides studied, the 125 Te chemical shift of dimethyl telluride can be correlated with the polarizability of the solvent.

Spectra and structure of phosphorus-boron compounds: VII. Vibrational analysis of solid phosphine-borane

Abstract The infrared (70–2700 cm − ) and Raman (25–2500 cm −1 ) spectra of H 3 PBH 3 , H 3 PBD 3 , D 3 PBH 3 and D 3 PBD 3 in the solid state at −196 °C have been recorded. The shift associated with the boron-10 and boron-11 isotopes was observed for the P-B stretching motion. A complete vibrational assignment is proposed and a normal coordinate calculation utilizing a valence force field model has been carried out. The force constant of 1.97 mdyn A −1 for the phosphorus-boron stretching mode is consistent with the relatively long phosphorus-boron bond; this constant is compared to the similar quantity for several other phosphorus-boron compounds. None of the E modes for the “free” molecule were found to be split. The number of observed lattice modes is not consistent with the crystal structure previously reported for this molecule. A possible explanation is discussed.

Spectra and structure of phosphorus–boron compounds. XXI. Microwave spectrum of ethylphosphine–borane

The microwave spectra of CH3CH2PH2 11BH3, CH3CH2PH2 10BH3, and CH3CH2PH2 11BD3 have been recorded in the region 18.0–39.0 GHz and those of CH3CH2PD2 11BH3 and CH3CH2PD2 11BD3 in the range 26.5–39.0 GHz. a‐type transitions were observed and R‐branch assignments have been made for all isotopes in the ground vibrational state. From the relative intensities of the microwave transitions, the Stark effect, and the experimental rotational constants, it has been determined that the assigned spectra result from the trans conformer which is believed to be more stable than the gauche form at ambient temperature. The dipole moment components for trans‐ethylphosphine–borane were determined from the Stark effect to be ‖μa‖ = 4.66±0.01, ‖μb‖ = 1.34±0.03, and ‖μt‖ = 4.85±0.02 D. With reasonable assumptions for the ethyl moiety, the following structural parameters for trans‐ethylphosphine–borane were calculated: r(B–P) = 1.914±0.018 A, r(B–H) = 1.205±0.013 A, r(P–H) = 1.408±0.016 A, r(P–C) = 1.823±0.016 A, ∢BPC = 115.0°±1...