Rb 6 LiPr 11 Cl 16 [SeO 3 ] 12 : Ein chloridisch derivatisiertes Rubidium‐Lithium‐Praseodym(III)‐Oxoselenat(IV)

Rb 6 LiPr 11 Cl 16 [SeO 3 ] 12 : A Chloride‐Derivatized Rubidium Lithium Praseodymium(III) Oxoselenate(IV) Transparent green square platelets with often truncated edges and corners of Rb 6 LiPr 11 Cl 16 [SeO 3 ] 12 were obtained by the reaction of elemental praseodymium, praseodymium(III,IV) oxide and selenium dioxide with an eutectic LiCl–RbCl flux at 500 °C in evacuated silica ampoules. A single crystal of the moisture and air insensitive compound was characterized by X‐ray diffraction single‐crystal structure analysis. Rb 6 LiPr 11 Cl 16 [SeO 3 ] 12 crystallizes tetragonally in the space group I 4/ mcm (no. 140; a = 1590.58(6) pm, c = 2478.97(9) pm, c / a = 1.559; Z = 4). The crystal structure is characterized by two types of layers parallel to the (001) plane following the sequence 121′2′1. Cl − anions form cubes around the Rb + cations (Rb1 and Rb2; CN = 8; d(Rb + −Cl − ) = 331 – 366 pm) within the first layer. One quarter of the possible places for Rb + cations within this CsCl‐type kind of arrangement is not occupied, however the Cl − anions of these vacancies are connected to Pr 3+ cations (Pr4) above and below instead, forming square antiprisms of [(Pr4)O 4 Cl 4 ] 9− units (d(Pr4−O) = 247–249 pm; d(Pr4−Cl) = 284–297 pm) that work as links between layer 1 and 2. Central cations of the second layer consist of Li + and Pr 3+ . While the Li + cations are surrounded by eight O 2− anions (d(Li−O5) = 251 pm) in the shape of cubes again, the Pr 3+ cations are likewisely coordinated by eight O 2− anions as square antiprisms (for Pr1, d(Pr1−O2) = 242 pm) and by ten O 2− anions (for Pr2 and Pr3), respectively. The latter form tetracapped trigonal antiprisms (Pr2, d(Pr2−O) = 251–253 pm and 4 × 262 pm) or bicapped distorted cubes (Pr3, d(Pr3−O) = 245–259 pm and 2 × 279 pm). The non ‐binding electron pairs (“ lone pairs ”) at the two crystallographically different Ψ 1 ‐tetrahedral [SeO 3 ] 2− anions (d(Se 4+ −O 2− ) = 169–173 pm) are directing towards the empty cavities between the layer‐connecting [(Pr4)O 4 Cl 4 ] 9− units.