Pnictogenide and Chalcogenide Zintl Phases via Solid State and Solvothermal Syntheses

Abstract

This work concentrated on the synthesis of new Zintl phases, especially focusing on the synthesis of new polyarsenides and chalcogenides. Through high temperature synthesis, the compounds Ba3As4, Ba3As2O and K3Ba7(As3)3O were successfully synthesised, whose structures are isotypical to known compounds. The main effort of this work was the synthesis of Zintl phases in liquid ammonia under mild and supercritical conditions. Advantage was taken of the fact that alkali metals and Europium form deep blue electride solutions of solvated electrons in liquid ammonia. These highly reactive solutions reacted with the chalcogens and pnictogens and formed polyanions. Thus, the phases Rb5(AsSe3)Se 2NH3, K9Se2.88(Se2)1.12OH, and [Eu(NH3)8]2[Eu(NH3)3(As7)2] could be obtained. A large number of the experiments were aimed at the synthesis of ternary compounds in the system AMAs/Ch (A=Na-Cs; M=Cu, Ag, Au; Ch=S, Se). Rb2AuAs7, Rb3AuSe2 1.5NH3, K2[AuSe]SeNH3 and K10CuSe8ClNH3 represent new members of this family. For the first time, the linear ion CuSe 32 with an extremely short Cu-Se bond length of 2.23 was obtained. Rb2AuAs7 is the first representative in the ternary system Rb-Au-As and contains one-dimensional chains of condensed As7 units. This polymeric anion 18 [As 37 ] has not yet been reported. As another important result of this work, the mixed chalcogenidoarsenates [As4S 26 ]and [As2Se 26 ], in [Mn(NH3)6][As4S6]NH3 and [Mn(NH3)6]2[As2Se6] were isolated from liquid ammonia. The cyclic [As4S 26 ] anion was observed in a new conformation. In parallel with these manganese-compounds, the polymeric solids As3NS3 and As3NSe3 formed, whose molecular structures are closely related to tris-(dimethylarsino)-amine (Me2As)3N. Syntheses in ethylenediamine led to the framework structure [Mn2(HPO3)2(C2H8N2)]. Analogous the spin-ladder compounds (NH4)Fe2S3 and (NH4)Fe2S3 were obtained. In these compounds, Fe is present in the mixed oxidation state +2.5. With the exception of two cases, the single crystal structures of all target compounds could be solved and refined. For K2[AuSe]SeNH3, a structural model could be presented despite pronounced twinning. For Rb3AuSe2 1.5NH3, the q-vector for an incommensurable modulated structure model could be defined with satellites of first order. A solution of the incommensurability was not possible due to weak intensity of the satellites, therefore the structure model does not take the modulation into account.