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Rb5[SiO4][OH] crystallizes in the monoclinc space group C2/m with a = 737.3(1) pm, b = 1073.7(2) pm, c = 1207.2(2) pm, β = 106.07(2)° and Z = 4 (single crystal data; R1= 0.0681 all data). Layers of edge-connected distorted trigonal prismatic [(OH)Rb6] entities and isolated tetrahedral [SiO4] units present the main structural features of this unprecedented structure type.

Na2Rb2SiO4 crystallizes in a hitherto unknown A2B2CX4 type of structure. The ortho-silicate anions and sodium cations form a three-dimensional structure of connected tetrahedral and trigonalbipyramidal units. The larger rubidium cations complement the cationic part of the structure and display the motif of corrugated hexagonal layers with Rb-Rb distances of less than 400 pm. Single crystal structure data (space group Pbca, Z = 8, a = 983.20(7), b = 1092.26(6), c = 1113.04(8) pm) are given and a comparison to other A2B2CX4-type of structures is presented.

Rb[NaCd3O4] presents, to the best of our knowledge, the first example of a 4d transition metal oxide in this A[(MO)4] structure type. The structure consists of a three-dimensional network of edge- and corner-linked distorted tetra­hedral [MO4] entities, with M = Na+ and Cd2+ in a 1:3 ratio sharing a common site set on Wyckoff position 8h in space group I4/m. The large cavities are occupied by A = Rb+ in an almost cubic coordination (4/m symmetry), giving rise to one-dimensional chains of face-sharing [RbO8] polyhedra along [001].

Rb7[SiO4][VO4]: an Ortho-Silicate-Vanadate(V) Rb7[SiO4][VO4] has been obtained from a redox reaction between CdO and vanadium metal in the presence of Rb2O and SiO2 at 600 °C in an Ag container as yellow-greenish transparent single crystals. The crystal structure determination (IPDS data: P21/c, a = 637.6(1) pm, b = 1039.7(1) pm, c = 2076.8(4) pm, β = 93.21(2)°, Z = 4, wR2 = 0.1319) reveals the presence of isolated complex anions, [SiO4]4— and [VO4]3—.

Na5[VO4][O] and Na4[VO4][OH] were obtained from reactions of V2O5 with Na2O and additional NaOH in the latter case, respectively, at 600-700 °C in sealed Ag containers under Ar atmosphere. The crystal structures have been determined from X-ray single crystal data. The structures contain isolated [VO4]3− complexes and non-coordinating oxide and hydroxide anions, respectively. Raman and infrared data is compared for both compounds and hydrogen bonding is discussed for Na4[VO4][OH].

Rb2NaMnO4 has been obtained from a redox reaction in silver crucibles. The crystal structure contains isolated [MnO4] units, which are slightly distorted from ideal tetra­hedral symmetry. Rb2NaMnO4 crystallizes isotypic with Cs2NaVO4 and Cs2NaAsO4.