SolutionNMRof the Light Main Group Metals

Abstract

Metal‐centered NMR spectroscopy in solution has long been an important complement to the nonmetal nuclei (e.g., 1 H, 13 C, and 31 P) routinely used in the NMR characterization of organic, organometallic, and coordination compounds. The chemical shifts of metal nuclei can be sensitive to small changes in molecular geometry and coordination number, revealing subtle differences in the solution composition of complexes, and can be used to study interchange mechanisms. This article is intended as an overview of the characteristics of the NMR‐active nuclei of the seven lightest metals as measured in solution, and as studied with computational methods. All of these elements (Li, Be, Na, Mg, Al, K, and Ca) possess one or more isotopes with nuclear spins that are potentially observable with solution NMR (nuclear magnetic resonance) techniques. They all possess quadrupole moments, and their resonances are often broad in asymmetric environments. Apart from those characteristics, they constitute a varied group, with their relative receptivity (a measure of their ease of observation) varying by a factor of over 400 000 to 1. Issues of detection and characteristic chemical shift ranges are discussed, with the aim of assisting the experimentalist in deciding whether metal‐based NMR will be useful in characterizing a system of concern and what information is likely to be obtained. An emphasis is placed on spectra obtained in nonaqueous solutions; in such media, ion‐pairing effects are the greatest, and it is where the species with the largest chemical shifts are typically found. Reviews on individual nuclei are cited where available.

Review—Polymer Electrolytes for Magnesium Batteries: Forging Away from Analogs of Lithium Polymer Electrolytes and Towards the Rechargeable Magnesium Metal Polymer Battery

“…Building upon diffusion NMR, electrophoretic 7 Li NMR has been applied to gain further insight into mobilities of 7 Li-containing species. [56][57][58][59][60] Unfortunately, none of the Mg isotopes is as receptive to NMR experiments (relative receptivity of 0.000268 for 25 Mg, compared with 0.27 for 7 Li and 1 for 1 H) 61 ; thus far, there are no reports of diffusion or electrophoretic NMR on magnesium isotopes. Thus, evaluating the transference number of magnesium electrolytes is not straightforward through either electrochemical or NMR techniques.…”

“…62 NMR.- 25 Mg is quadrupolar with a spin number of 5/2 and relative receptivity of 2.68 × 10 −4 . 61,68 Those characteristics of 25 Mg results in lower signal intensity and a broadened peak, which makes the analysis of 25 Mg NMR more complicated and less common. 69 Recently, 25 Mg solid-state NMR was performed to investigate the interaction between Mg ions and PEO.…”