Relaxation studies of carbonyl rhenium clusters. Part 2—relaxation mechanisms and estimation of the 13C chemical shielding anisotropy in the [Re3(μ‐H)4(CO)10]− anion at low temperature

Abstract

AbstractApplication of the non‐selective inversion recovery technique to 13C spectra of moderately enriched [Re3(μ‐H)4(CO)10]− indicates that relaxation times, at low temperatures, are strongly field dependent and decrease with increasing field strength. Measurements performed at 183 K and at 20.15, 50.31 and 67.88 MHz indicate that chemical shielding anisotropy is dominant at higher fields, which differs from the behaviour previously observed at room temperature where the main relaxation pathway is scalar coupling with the quadrupolar rhenium isotopes. The 13C chemical shielding anisotropy was estimated to be in the range 476±40 ppm. Interactions with quadrupolar rhenium also affect the hydrogen spin‐spin relaxation times.