Na_2.9KMo₁₂S₁₄: a novel quaternary reduced molybdenum sulfide containing Mo₁₂ clusters with a channel structure

The crystal structure of tris­odium potassium dodeca­molybdenum tetra­deca­sulfide, Na_2.9 (2)KMo₁₂S₁₄, consists of Mo₁₂S₁₄S₆ cluster units inter­connected through inter­unit Mo-S bonds and delimiting channels in which the Na⁺ cations are disordered. The cluster units are centered at Wyckoff positions 2d and have point-group symmetry 3.2. The K atom lies on sites with 3.2 symmetry (Wyckoff site 2c) between two consecutive Mo₁₂S₁₄S₆ units. One of the three independent S atoms and one Na atom lie on sites with 3.. symmetry (Wyckoff sites 4e and 4f). The other Na atom occupies a 2b position with -3.. symmetry. The crystal studied was a merohedral twin with refined components of 0.4951 (13) and 0.5049 (13).

Na_3.88Mo₁₅Se₁₉: a novel ternary reduced molybdenum selenide containing Mo₆ and Mo₉ clusters

The structure of tetrasodium penta­deca­molybdenum nona­deca­selenide, Na_3.88Mo₁₅Se₁₉, is isotypic with the In_3+xMo₁₅Se₁₉ compounds [Grüttner et al. (1979). Acta Cryst. B35, 285-292]. It is characterized by two cluster units, Mo₆Seⁱ₈Se^a₆ and Mo₉Seⁱ₁₁Se^a₆ (where i represents inner and a apical atoms), that are present in a 1:1 ratio. The cluster units are centered at Wyckoff positions 2b and 2c and have point-group symmetry -3 and -6, respectively. The clusters are inter­connected through additional Mo-Se bonds. In the title compound, the Na⁺ cations replace the trivalent as well as the monovalent indium atoms present in In_3.9Mo₁₅Se₁₉. One Mo, one Se and one Na atom are situated on mirror planes, and two other Se atoms and one Na atom [occupancy 0.628 (14)] are situated on threefold rotation axes. The crystal studied was twinned by merohedry with refined components of 0.4216 (12) and 0.5784 (12).