H-1 AND C-13 NMR-STUDY OF THE SOLID-STATE DYNAMICS OF H4RU4(CO)12

Variable temperature C-13-{H-1} CP/MAS, H-1 MAS and H-1 wide-line NMR spectra of H4Ru4-(CO)12 are interpreted in terms of a dynamic process involving either the H4RU4 moiety as a whole or the motion of the hydrides over the surface of the metallic core. The temperature dependence of the H-1 spin-lattice relaxation time (T1) values over the range 298-360 K and the temperature dependence of the line width of the static H-1 spectrum over the range 153-380 K together give an activation energy for this motional process of 67.2 +/- 8.0 kJ mol-1. The rigidity of the carbonyl polyhedron is demonstrated by the fact that the C-13 chemical shift tensor components are typical for those in a nonfluxional molecule and are invariant between 200 and 360 K.