Orientations of the principal components of electric field gradients and internal motions in dihydrogen ligands from the ²H T₁ NMR relaxation data in solution

Abstract

The deuterium spin-lattice relaxation times in (D2) ligands of W, Ru and Os complexes are reviewed and analyzed in terms of the fast internal (D2) motions: free rotation, librations and 180 degrees jumps. The analysis was performed using quadrupolar coupling constant (DQCC) parameters taken from the solid-state 2H NMR spectra and density function theory calculations. It is shown that the calculated DQCC values can be corrected for further use in interpretations of deuterium relaxation times for Ru and Os dihydrogen complexes. The resulting data led to a criterion for using the relaxation data to distinguish fast-spinning dihydrogen ligands. It is shown that the principal components of electric field gradient tensors at D in the dihydrogen ligands are oriented closer to M-D directions.

Layered metal(IV) phosphonate materials: Solid‐state 1H, 13C, 31P NMR spectra and NMR relaxation

“…At the same time, there is always a chance to have a short proton‐proton contact due to rotation of a neighboring ring. In other words, for protons, this rotation looks more complicated and more anisotropic, and this feature can actually result in the temperature displacement of the 1 H T 1min time …”

“…Equation is valid for isotropic motions, but the phenylene rotation in Figure is actually anisotropic. Such a limited motion (even when very rapid) cannot fully average proton‐proton dipolar interactions; therefore, the 1 H signal remains broad in Figure at the line width of 18.2 kHz at 343 K and 22 kHz at 223 K. As has been shown earlier, when an isotropic model is applied for anisotropic motions, the ΔE value is still meaningful, and the correlation time constant τ 0 and the r(P‐H) distance can be effective parameters. In fact, a τ 0 value determined for 2 from the treatment in Figure was found to be 3.3 × 10 −8 s, which is large compared to the ~10 −12 s expected for simple motions.…”

Grasping hydrogen adsorption and dynamics in metal–organic frameworks using 2H solid-state NMR

“…18 Observed C Q ( 2 H) values in Mg-MOF-74 are far less than 225 kHz, and are also smaller than the C Q ( 2 H) range of ca. 30-120 kHz associated with Z 2 bonding between a metal and D 2 in metal-dihydrogen complexes, 18,[28][29][30] implying that fast D 2 motion exists here and that the metal-D 2 interactions in Mg-MOF-74 are weaker than the bonding in metal-dihydrogen complexes. It should be noted that at the experimental temperatures and magnitudes of quadrupolar coupling in this study, any spectral effects arising from D 2 rotational tunneling are expected to be negligible.…”

Sigma Bonds as Ligand Donor Groups in Transition Metal Complexes

“…Combined with density functional theory calculations, this work led to a criterion for using the relaxation data to distinguish rapidly spinning dihydrogen ligands from nonrotating ones. Not only free rotation but librations and 180 jumps in a twofold potential were also considered in the analysis ( [28] and references cited).…”