Solid state H-2 NMR study of the orientation and dynamics of cobaltoceniumintercalated in the layered silicate LaponiteRD

Ion-exchange intercalation of [Co(eta-C5D5)(2)](+) ions in the smectite cla y LaponiteRD [Na0.46Mg5.42Li0.46Si8(OH)(4)O-20] yields [Mg5.42Li0.46Si8(OH) (4)O-20{Co(eta-C5D5)(2)}(0.4)Na-0.1]. Structural and dynamic information ab out the material was obtained with the benefit of H-2 NMR spectroscopic mea surements, performed on powder and specially prepared oriented samples, com bined with comparisons to H-2 NMR lineshape simulations. The cobaltocenium cations adopt an ordered arrangement in the host lattice with their princip al molecular axes parallel to the silicate layers. In addition to rotation about the principal molecular axis, previously observed for similar cobalto cenium layered intercalates, the emergence of an inner component with a spl itting of 22.3 kHz over the temperature range 220-300 K strongly suggests t he molecule is undergoing n-fold reorientations about the C-2 axis of symme try. Concurrent to this dynamic motion is an additional vibrational motion in and out of the plane parallel to the silicate layers. Coupled with rotat ion about the C-2 axis, this gives rise to a gyratory motion in the slow-in termediate regime which increases with temperature until the fast regime is reached at 330 K.