High-resolution H-2 MAS NMR applied to deuterium analogs of hydrido eta(2)-dihydrogen complexes

H-2 solid-state, variable temperature magic angle spinning (MAS) NMR spectra of precipitated samples of the deutero dideuterium complexes Ru(D)(2)(eta(2)-D-2)(2)(PCy3)(2) and RuD(eta(2)-D-2)I(PCy3)(2) Cy = cyclohexyl are presented. They show that even at moderate MAS speed, high resolution is achieved at 7 and 14T allowing H-2 chemical shifts and quadrupole couplings to be obtained and assigned to different solid and gaseous H-2 species. These two parameters allow identifying chemically different hydrogen species in the material. The analysis of these parameters in this study reveals the presence of three different species in the sample, namely the complexes RuD(eta(2)-D-2)I(PCy3)(2) and RuD(eta(2)-D-2)(2)I(PCy3)(2). and highly mobile HD/D-2. These assignments are supported by H-2 T-1 relaxation times and P-31 MAS NMR spectra. Moreover, variable temperature MAS NMR spectra reveal temperature-dependent line-shape changes, which are clear indications of intramolecular hydrogen exchange of the deutero and the dideuterium ligands and which give an estimate for the activation energy of this process. (C) 2009 Elsevier Inc. All rights reserved