The proton magnetic resonance (1H NMR) spectra of Ca(NH3)6, Ba(NH3)6, and Li(NH3)4 have been recorded in the temperature range 20-150 K using a broad-line, symmetrical-bridge spectrometer. In the hexaammines very narrow first-derivative line widths are observed (<2.5 G in the range 20-150 K). Significant changes occur in the 1H NMR spectra of Ca(NH3)6 in the ranges 20-50, 60-80, and 100-130 K, whereas in Ba(NH3)6 changes occur between 70 and 100 K and above 140 K. The line width and its temperature dependence are interpreted in terms of structure, phase transitions, and molecular motion. In the high-temperature region very large, temperature-independent, high-field shifts of about 0.3 G (160 ppm) have been measured in both Ca(NH3)6 and Ba(NH3)6. The shifts are tentatively interpreted in terms of indirect coupling of the type found in aromatic radicals.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry