Proton NMR and covalency parameters of ruthenium (III) hexaammine

The NMR signal of the ammine protons of the Ru(NH₃) ₆³⁺ ion was directly measured by a wide line technique at various temperatures. A non-Curie behavior of the paramagnetic chemical shift was observed and the ligand pseudocontact interaction suggested by Kurland and McGarvey was used for its interpretation. The contact hyperfine interaction with the ammine protons was found to be A = 5.9 MHz. The covalency parameter was calculated as λ = 0.33, but after allowing for cross-term spin densities it was reduced to 0.28. The NMR relaxation times are discussed in terms of the ruthenium proton distance and the electronic spin relaxation times of the Ru(NH₃)₆³⁺ ion.