| Abstract: | Chromium Hexacyano Complexes: The Crystal Structures of the Cyano Elpasolites (NMe4)2ACr(CN)6 (A = K, Cs) and of the Cubic Barium Compound Ba3Cr(CN)6]2 · 20 H2O The crystal structures of the cyano elpasolites (NMe4)2KCr(CN)6 (a = 1527.3(1), b = 888.1(1), c = 1539.0(1) pm, β = 109.92(1)°; C2/c, Z = 4) and (NMe4)2CsCr(CN)6 (a = 1278.9(1) pm; Fm3m, Z = 4), as well as of the cubic compound Ba3Cr(CN)6]2 · 20 H2O (a = 1631.0(1) pm; Im3m, Z = 4) were determined by X‐ray methods with single crystals. Reasons for the enlarged distances within the Cr(CN)6]3–‐octahedron of the K compound (Cr–C: 209.3 pm) compared to the observations within both cubic complexes (206.1 resp. 206.9 pm) are discussed in context with the tolerance factors of cyano elpasolites. As is the case there concerning the cyano bridges Cr–CN–A towards the alkali ions the novel structure type of the barium compound, too, exhibits nearly linear bridging towards Ba. It contributes, however, only four N ligands to the ninefold BaN4O5] coordination; part of the aqua ligands show disorder (Ba–N: 287.5, Ba–O: 281/293 pm). |
