X-ray diffraction, XPS, and magnetic properties of lanthanide-based misfit-layered sulfides intercalated with cobaltocene

Polycrystalline (CeS)(1.15)(TaS2)(2) and (SmS)(1.19)(TaS2)(2), two composite misfit-layered sulfides, react directly with cobaltocene (CoCp2) in acetonitrile solutions to form novel intercalation compounds of composition (CeS)(1.15)(TaS2)(2)(CoCp2)(0.31) and (SmS)(1.19)(TaS2)(2)(CoCp2)(0.30), respectively. Their powder X-ray diffraction data reveal a significant expansion (ca.5.5 A) along the c-axis and preservation of the a-b-axis dimensions. One-dimensional electron density calculations are consistent with a model where the guest molecule is located at all TaS2-TaS2 interfaces, whereas MS-TaS2 (M = Ce, Sm) interfaces remain empty. The Ce and Sm 3d core-level spectra reveal that these elements are present mainly as tervalent ions. The magnetic properties of the Ce compound are consistent with this valence state. Although the intercalation of cobaltocene does not shift the binding energies of the host constituent elements appreciably, the organometallic molecule is intercalated as CoCp2+ ions, as is usually the case with layered chalcogenide hosts. In the case of the Ce system, this model is also supported by the magnetic data and suggests that the electron donated by the guest molecule is transferred to the conduction band of the TaS2 layers, whereas the lanthanide element remains as a trivalent ion. The formal electron transfer apparently taking place from the MS bilayer (M = Ce, Sm) to TaS2 sheets does not prevent ionization of cobaltocene.