Quadrupolar bond with

Mo NMR data for several carbonylate species, [Mo(CO)sX] and [Mo2(CO)ioX] (X = halide, pseudohalide), are given in Table 2, arranged in order of increased deshielding of the Mo nucleus. Clearly, the chemical shifts observed are independent of the counter-ion present and show minimal susceptibility to solvent effects. The broader line widths, relative to those observed for Mo(CO)6 (see Table 1), are most likely due to reduced symmetry at the Mo nucleus upon substitution of the CO ligands. Brownlee et al. have found that for Mo(CO)sL (L = Cr, py, PPhs, AsPhs and SbPhs) the spin lattice relaxation times (Tj) are due entirely to a quadrupolar mechanism with no scalar contribution to the line width where the Mo is bonded to another quadrupolar nucleus. Some related higher substitution anionic species are discussed later in this review (see Sections 2.1.4 and 2.1.5). 

A few solvents exhibit intermediate properties. For example, both BTF (Ref. 22) and F-626 (Ref. 23 see Section 3.1) are able to dissolve appreciable quantities of both fluorous and non-fluorous solutes. Other solvents are often mistakenly assumed to be fluorous. Of these, the most important are perfluoroarenes such as hexafluo-robenzene. The arene tt clouds and sp carbon-fluorine bonds lead to significant intermolecular bond dipoles, induced dipoles and quadrupolar interactions with non-fluorous molecules. ... 

If the principal axis frame (a, 6, c) for the quadrupolar interaction with the b axis in the direction of the ith C- H bond is selected and the reasonable assumption is made that is diagonal and independent of the conformation label, then... 

Deuterium, whose spin is equal to 1, is a quadrupolar nucleus. Its NMR parameters are almost exclusively governed by the quadrupolar interaction with the electric field tensor (FGT) at the deuteron site. Although the intermolecular contributions to the electric field gradient can be significant, the field gradient usually originates mainly from the electrons in the C- H bond and is considered to a first approximation to be intramolecular. It is found to be axially symmetric about the C- H bond in aliphatic compounds, and to a good approximation in aromatic compounds as well. Thus, information obtained from H NMR on molecular order and dynamics mostly concerns individual C- H bond directions. 

A number of isotopically labelled organogermanium compounds have been prepared and subjected to spectroscopic investigation (microwave, infrared and Raman) with a view to obtaining structural information about the compound. More specifically, these studies have sought information on bond strengths, bond lengths, dipole moments, quadrupolar... 

The NMR experiments were performed using the quadrupolar echo pulse sequence 7i/2x—Ti—7i/2y—T2—acquisition with phase-cycling and quadrature detection. A Bruker MSL 400 spectrometer was used for the high pressure studies operating at a resonance frequency of 61.4 MHz. In the liquid-crystalline phase, perdeuterated lipids display NMR spectra, which are superpositions of axially symmetric quadrupolar powder patterns of all C-D bonds.From the sharp edges, the quadrupolar splittings... 

The magnitude of the chemical shift anisotropy depends on the bonding situation and the nucleus gyromagnetic ratio. Since the bonds formed by lithium in organolithium compounds or other lithiated systems are mainly ionic, the anisotropy of the lithium chemical shift is generally small. It is more pronounced for Li than for Li. Li spectra are dominated by the quadrupolar effect and the CSA contribution to the Li lineshape is often negligible. Exceptions are compounds with poly-hapto bound lithium, such as... 

Numerous X-ray investigations have unravelled the solid state structure of contact and solvent-separated ion pairs. It was therefore considered to be of interest to evaluate also the potential of solid state NMR as a tool for the investigation of this structural problem. In addition to the study of chemical shifts discussed above (Section II.B), the quadrupole coupling constant of the nuclide Li, x( Li), was expected to be an ideal sensor for the bonding situation around the lithium cation because, due to its dependence on the electric field gradient, the quadrupolar interaction for this spin-3/2 nucleus is strongly influenced by local symmetry, as exemplified in Section II.C.3. This is also shown with some model calculations in Section ILF. 

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