High-resolution 31P-{ 1H} nuclear magnetic resonance studies of Group IB metal heteronuclear cluster compounds in the solid state

Abstract

High-resolution 31P-{ 1H} NMR spectra of a series of crystalline mixed-metal cluster compounds containing M(PR 3) (M = Cu, Ag, or Au; R = alkyl or aryl) fragments have been recorded using magic angle sample spinning. The solid-state spectra are compared with those measured for the same compounds in solution and the values of the chemical shifts and, for the silver-containing species, the magnitudes of J( 107,109AgP) av, are generally very similar. The solid-state NMR spectra suggest that the dynamic processes involving hydrido ligand site-exchange or intermolecular exchange of PR 3 ligands between clusters, which have been previously observed at ambient temperature in solution for some of the clusters studied, do not occur or are not sufficiently rapid to be detected when the same compounds are in the crystalline state. In addition, the intramolecular metal core rearrangements, which all of the bimetallic clusters containing inequivalent M(PR 3) fragments undergo at ambient temperature in solution, are also not observed by solid-state NMR spectroscopy in the crystalline compounds. For some of the clusters of this latter class, the solid-state spectra can provide useful structural information about the ground-state metal framework geometries which it is impossible to obtain from solution studies, even at low temperatures.