New sodium-rich mixed Mn/In chalcogenido metallates Na 12 MnIn 2 Q 10 (Q = S, Se)

Abstract

Abstract The sodium-rich sulfido and selenido metallates Na12MnIn2 Q 10 (Q = S/Se) were synthesized in pure phase from melts composed of stoichiometric quantities of the manganese monochalcogenides MnQ, elemental indium and the chalcogens together with either Na2S (Q = S) or elemental sodium (Q = Se) as starting material. The samples were heated up to maximum temperatures of 1000/900 °C under an argon atmosphere; crystallization was achieved by slow cooling rates of 10 K h−1. The two isotypic compounds (monoclinic, space group P21/m, a = 678.26(2)/698.85(10), b = 2202.77(7)/2298.7(3), c = 766.39(3)/800.59(13) pm, β = 90.232(2)/90.147(5)°, Z = 2, R1 = 0.0516/0.0575) crystallize in a new structure type. According to the division of the formula as Na12[InQ 4][MnInQ 6] the salts contain ortho indate anions [InIII Q 4]5− besides hetero-bimetallic dimers [MnIIInIII Q 6]7−, which consist of two edge-sharing [MQ 4] tetrahedra. The seven crystallographically different sodium cations exhibit an either tetrahedral or octahedral coordination by the chalcogen atoms. Thus, the overall structure of the salt is best described by a hexagonal close packing of the sulfide/selenide anions, in which the octahedral voids of every second interlayer section are fully occupied by the (overall 5/f.u.) Na + positions with CN = 6. In the other half of the interlayer sheets, all tetrahedral voids (overall 10/f.u.) are occupied by the seven CN = 4 Na + cations, one In3+ of the ortho anion and the two Mn2+/In3+ cations (which statistically occupy one crystallographic site). This structure relation is also verified by a Bärnighausen group-subgroup tree connecting the h.c.p. (Mg type) aristotype (with its tetrahedral and octahedral voids) by an overall index of 60 with the structure of the two title compounds.