Anisotropy of the proton spin–lattice relaxation time in the superconducting intercalation complex TaS2(NH3): Structural and bonding implications

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Abstract
The nature of the interaction responsible for the formation of molecular intercalation complexes between Lewis bases and layered transition metal dichalcogenides is not well understood. To some extent this is due to a lack of structural information. A prototype of these complexes is TaS2(NH3), in which monolayers of ammonia are inserted between the metallic, superconducting layers of TaS2. The compound is crystalline and stoichiometric. Measurement of the anisotropy of the proton spin–lattice relaxation time at 300 °K indicates that the molecular threefold symmetry axis is not perpendicular to the disulfide layers as suggested by other workers, but is parallel to the layers. This orientation precludes direct interaction between the molecular lone pair orbital and the transition metal atoms. The interactions governing the structure of this complex may be similar to those obtaining in the intercalation complexes between TaS2 and a number of substituted pyridines, in which complexes the axis of the lone pair orbital is also parallel to the layers.