The first rubidium rare-earth(III) thiophosphates: Rb3M3[PS4]4 (M=Pr, Er) |
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Authors: | Theresa Komm |
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Institution: | Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany |
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Abstract: | The two non-isotypical rubidium rare-earth(III) thiophosphates Rb3M3PS4]4 of praseodymium and erbium can easily be obtained by the stoichiometric reaction of the respective rare-earth metal, red phosphorus and sulfur with an excess of rubidium bromide (RbBr) as flux and rubidium source at 950°C for 14 days in evacuated silica tubes. The pale green platelet-shaped single crystals of Rb3Pr3PS4]4 as well as the pink rods of Rb3Er3PS4]4 are moisture sensitive. Rb3Pr3PS4]4 crystallizes triclinically in the space group ( , , , α=84.329(4)°, β=88.008(4)°, γ=80.704(4)°; Z=2), Rb3Er3PS4]4 monoclinically in the space group P21/n ( , , , β=95.601(6)°; Z=4). In both structures, there are three crystallographically different rare-earth cations present. (M1)3+ is eightfold coordinated in the shape of a square antiprism, (M2)3+ and (M3)3+ are both surrounded by eight sulfur atoms as bicapped trigonal prisms each with a coordination number of eight as well as for the praseodymium, but better described as CN=7+1 in the case of the erbium compound. These MS8]13− polyhedra form a layer according to by sharing edges with the isolated PS4]3− tetrahedra (d(P-S)=200-209 pm, ?(S-P-S)=102-116°). These layers are stacked with a repetition period of three in the case of the praseodymium compound, but of only two for the erbium analog. The rubidium cation (Rb1)+ is located in cavities of these layers and tenfold coordinated in the shape of a tetracapped trigonal antiprism. The also tenfold but more irregularly coordinated rubidium cations (Rb2)+ and (Rb3)+ reside between the layers. |
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Keywords: | Thiophosphates Rare-earth compounds Rubidium salts Crystal structure |
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