2H Solid-State NMR of Ruthenium Complexes

The H-2 solid-state NMR spectra of the transition metal complexes Tp*RuD(THT)(2) (1a), Tp*RuD(D-2)(THT) (1b), Tp*RuD(D-2)(2) (1c), Cp*RuD3(PPh3) (2) and RuD2(eta(2)-D-2)(2)(PCY3)(2) (3) have been measured in a wide temperature range. These compounds were chosen as potential model systems for hydrogen surface species in Ru-nanoparticles. The deuterium quadrupolar coupling constants Q(cc) and asymmetry parameters were extracted by H-2 NMR line-shape analysis. The Q(cc) c values of the deuterons bound to the metal vary between 13 kHz and 76 kHz. In addition all spectra show that some of the deuterium is incorporated into carbon positions exhibiting quadrupolar coupling constants in the range of 134 kHz to 192 kHz. The room temperature spectra contain an additional weak very narrow line which was assigned to deuterons exhibiting a high mobility. These deuterons are attributed to crystallographic impurity and partially to D-2 molecules which lost by the complexes. The temperature where their motion is quenched and the types of these motions depend on the chemical structure. We propose to use the values of the quadrupolar coupling constants measured in order to characterize different hydrogen species on the surface of Ru-nanoparticles.