The first chromium-53 solid-state nuclear magnetic resonance spectra of diamagnetic chromium(0) and chromium(VI) compounds

Abstract

Chromium-53 is a spin-3/2 nucleus with a relatively small magnetic moment, low natural abundance, and large quadrupole moment. These properties have severely hampered the development of ⁵³Cr NMR, especially in the solid state. In this Communication, the first ⁵³Cr solid-state NMR spectra of prototypal diamagnetic chromium(0) and chromium(VI) compounds are presented. Specifically, analyses of ⁵³Cr NMR spectra of solid hexacarbonylchromium(0), caesium chromate(VI), and potassium chromate(VI) have allowed for the determination of ⁵³Cr quadrupolar coupling parameters and the first chromium chemical shift (CS) tensors. This work demonstrates the potential of ⁵³Cr solid-state NMR, in particular the extreme sensitivity of the ⁵³Cr quadrupolar coupling constant to the local chromium environment. Comparisons are made to known ⁵³Cr NMR parameters available from solution studies, and to the ⁹⁵Mo solid-state NMR parameters of analogous molybdenum compounds. The influence of crystal symmetry present in isomorphic Cr(CO)₆ and Mo(CO)₆ is strongly reflected in the magnitudes of the metal nuclei CS tensors and in their orientation with respect to their corresponding electric field gradient tensors.