Synthesis, electronic and crystal structures, and physical studies of the superconductor Cs(~1)Mo12S14, final step of the condensation of the Mo6L8(i)L6(a) unit.

The ternary reduced molybdenum sulphide Cs∼1Mo12S14 has been synthesized by solid-state reaction at 1400 °C for 96 h in sealed molybdenum crucibles. The compound crystallizes in the trigonal space group P31c with the following lattice parameters: a = 9.9793 (2) A, c = 6.3730 (2) A, Z = 1. Its crystal structure was determined from single crystal X-ray diffraction data and consists of interconnected Mo6S8iS6a units forming an original three-dimensional framework in which large tunnels are occupied randomly by the Cs+ ions. 133Cs static NMR studies are in favor of a static cesium disorder. Unlike Ba4Mo12S18 where some Mo6S8iS6a units are also connected through Si-i ligands, this connection mode does not lead to significant interactions in the title compound. Single-crystal resistivity measurements show that Cs∼1Mo12S14 presents a metallic behavior with a superconducting transition at 7.7 K as confirmed by magnetic measurements.