Thiosilicate der Selten‐Erd‐Elemente: III. KLa[SiS4] und RbLa[SiS4] – Ein struktureller Vergleich

Thiosilicates of the Rare‐Earth Elements: III. KLa[SiS₄] and RbLa[SiS₄] – A Structural Comparison Pale yellow, platelet shaped, air‐ and water resistant single crystals of KLa[SiS₄] derived from the reaction of lanthanum (La) and sulfur (S) with silicon disulfide (SiS₂) in a molar ratio of 2 : 3 : 1 with an excess of potassium chloride (KCl) as flux and source of potassium ions in evacuated silica ampoules at 850 °C within seven days. The analogous reaction utilizing a melt of rubidium chloride (RbCl) instead also leads to yellow comparable single crystals of RbLa[SiS₄]. The potassium lanthanum thiosilicate crystallizes monoclinically with the space group P2₁/m (a = 653.34(6), b = 657.23(6), c = 867.02(8) pm, β = 107.496(9)°) and two formula units per unit cell, while the rubidium lanthanum thiosilicate has to be assigned orthorhombically with the space group Pnma (a = 1728.4(2), b = 667.23(6), c = 652.89(6) pm) and four formula units in its unit cell. In both compounds the La³⁺ cations are surrounded by 8+1 sulfide anions in the shape of tricapped trigonal prisms. The Rb⁺ cations in RbLa[SiS₄] show a coordination number of 9+2 relative to the S^2? anions, which form pentacapped trigonal prisms about Rb⁺. This coordination number, however, is apparently too high for the K⁺ cations in KLa[SiS₄], so that they only exhibit a bicapped trigonal prismatic environment built up by eight S^2? anions. The isolated thiosilicate tetrahedra [SiS₄]^4? of the rubidium compound are surrounded by La³⁺ both edge‐ and face‐capping, but terminal as well as edge‐ and face‐spanning by Rb⁺. In the potassium compound there is no change for the La³⁺ environment about the [SiS₄]^4? tetrahedra, but the K⁺ cations are only able to attach terminal and via edges. The whole structure is built up by anionic equation/tex2gif-stack-1.gif{La[SiS₄]}^? layers that are separated by the alkali metal cations. In direct comparison the two thiosilicate structures can be regarded as stacking variants.     

Thiosilicate der Selten‐Erd‐Elemente: II. Die nichtzentrosymmetrischen Caesium‐Derivate CsM[SiS4] (M = Sm — Tm)

Thiosilicates of the Rare‐Earth Elements: II. The Noncentrosymmetric Cesium Derivatives CsM[SiS₄](M = Sm — Tm) The cesium lanthanoid thiosilicates CsM[SiS₄] (M = Sm — Tm) all crystallize orthorhombically in the noncentrosymmetric space group P2₁2₁2₁ with four formula units per unit cell. The lattice constants show values within the following ranges: a = 630 — 640 pm, b = 665 — 673 pm and c = 1763 — 1778 pm. The reaction of lanthanoid metal (M) with sulfur (S) and silicon disulfide (SiS₂) with an excess of cesium chloride (CsCl) serving both as flux medium and as reactand (Cs⁺ source) in evacuated silica ampoules for seven days at 850 °C leads to air‐ and water‐resistant platelet‐shaped single crystals that exhibit the colour of the lanthanoid trication (M³⁺) with a slight yellowish shade. The crystal structure arranges in layers since anionic {M[SiS₄]}^— sheets get alternatingly piled with those of Cs⁺ cations. The M³⁺ cations are surrounded capped trigonal prismatically by seven sulfide anions whereas the Cs⁺ cations have an environment of nine plus two S^2— in the shape of a fivefold overcapped trigonal prism. All sulfide anions belong to almost ideal tetrahedral ortho‐thiosilicate units [SiS₄]^4—.     

Sm4S3[Si2O7] und NaSm9S2[SiO4]6: Zwei Sulfidsilicate mit dreiwertigem Samarium

Sm₄S₃[Si₂O₇] and NaSm₉S₂[SiO₄]₆: Two Sulfide Silicates with Trivalent Samarium The sulfide silicates Sm₄S₃[Si₂O₇] and NaSm₉S₂[SiO₄]₆ are obtained as light yellow transparent crystals by the reaction of Sm, Sm₂O₃, S, and SiO₂ with fluxing SmCl₃ or NaCl, respectively, in suitable molar ratios in fused evacuated silica tubes (850 °C, 7 d). Tetragonal crystals of Sm₄S₃[Si₂O₇] (I4₁/amd; Z = 8; a = 1186.4(1); c = 1387.0(2) pm) with ecliptically conformed [Si₂O₇]^6–‐groups of corner sharing [SiO₄]‐tetrahedra are formed. These double tetrahedra as well the sulfide anions (S^2–) coordinate two crystallographically independent metal cations. They provide coordination numbers of 8 + 1 (5 S^2– and 3 + 1 O^2–) for Sm1 and 9 (3 S^2– and 6 O^2–) for Sm2. NaSm₉S₂[SiO₄]₆ crystallizes hexagonally (P6₃/m; Z = 1; a = 975.32(9); c = 676.46(7) pm) in a modified bromapatite‐type structure. The coordination spheres about the two crystallographically different Sm³⁺ cations are built up by oxygen atoms of the orthosilicate units ([SiO₄]^4–) and sulfide anions (S^2–). As a result, Sm1 and Sm2 have coordination numbers of 9 and 8, respectively. Na⁺ and (Sm1)³⁺ occupy the position 4 f in a molar ratio of 1 : 3 whereas the lower coordinated (Sm2)³⁺ occupies the 6 h position.     

Thiosilicate der Selten‐Erd‐Elemente: I. Die isotypen Verbindungen KCe[SiS4] und Eu2[SiS4]

Thiosili‐Thiosilicates of the Rare‐Earth Elements: I. The Isotypic Compounds KCe[SiS₄] and Eu₂[SiS₄] Both isotypic thiosilicates KCe[SiS₄] (a = 649.15(6), b = 656.18(6), c = 863.96(8) pm, β = 107.531(9)°) and Eu₂[SiS₄] (a = 651.71(6), b = 659.54(6), c = 821.93(8) pm, β = 108.437(9)°) crystallize monoclinically in the space group P2₁/m and Z = 2. By the reaction of KCl, Ce₂S₃ and SiS₂ in the ratio 1 : 1 : 1 using a sixfold molar amount of KCl as flux in evacuated silica tubes (7 d, 850°C) brownish yellow, plate‐shaped single crystals, resistant both to air and water are obtained. The conversion of Eu, S and SiS₂ in molar ratios of 2 : 2 : 1 with an excess of CsCl as flux in evacuated silica tubes (7 d, 850°C) leads to deep red, plate‐shaped single crystals, which remain air‐ and water‐stable for a few days. The crystal structure contains isolated ortho‐thiosilicate units, that together with the Ce³⁺ or (Eu2)²⁺ cations build corrugated anionic layers parallel (001) according to {(Ce[SiS₄])^—} and {(Eu2[SiS₄])^2—}, respectively. These layers are alternatingly piled with cationic layers consisting solely of K⁺ or (Eu1)²⁺ cations. The latter show coordination numbers of eight in the shape of a bicapped trigonal prism, whereas the cations of the position Ce³⁺ and (Eu2)²⁺ have a (2+1)‐fold capped trigonal prismatic environment with a coordination number of 8+1. The comparison of both compounds KCe[SiS₄] and Eu₂[SiS₄] (≡ EuEu[SiS₄]) demonstrates, that Eu²⁺ is able to substitute both K⁺ and Ce³⁺ isomorphically.     

Potassium sodium tin selenide,K3NaSn3Se8

The title compound, tripotassium sodium tritin octaselenide, K₃NaSn₃Se₈, has a molecular (zero‐dimensional) structure containing trimeric [Sn₃Se₈]^4? units which consist of three edge‐sharing SnSe₄ tetrahedra. The [Sn₃Se₈]^4? anions and the tetrahedrally coordinated Na⁺ cations are arranged in an alternating fashion along the c axis to form SiS₂‐like chains, which are then separated by eight‐coordinate K⁺ cations. The Sn—Se bond distances are normal, being in the range 2.477 (1)–2.612 (1) Å.     

K2NdP2S7: A Mixed‐Valent Neodymium(III) Thiophosphate According to K4Nd2[PS4]2[P2S6] with Discrete [PS4]3– and [S3P–PS3]4– Anions

Pale blue, lath‐shaped single crystals of K₂NdP₂S₇ (≡ K₄Nd₂[PS₄]₂[P₂S₆]; monoclinic, P2₁/n, a = 904.76(8), b = 677.38(6), c = 1988.7(2) pm, β = 97.295(5)°, Z = 2) are obtained by the reaction of Nd, S and P₂S₅ with an excess of KCl as a flux in evacuated silica tubes at 750 °C (7 d) which should produce Nd[PS₄] instead. Beside isolated [PS₄]^3– tetrahedra, the crystal structure contains discrete ethane‐analogous [P₂S₆]^4– (≡ [S₃P–PS₃]^4–) units in staggered conformation with tetravalent phosphorus cations and a P–P distance of 219 pm. The two crystallographically different potassium cations show coordination numbers of nine and ten in the shape of distorted mono‐ and bicapped square antiprisms. Finally, the Nd³⁺ cations are surrounded by eight sulfur atoms arranged as (uncapped) square antiprisms. The entire structure is dominated by (K1)⁺ containing {(Nd₂[PS₄]₂[P₂S₆])^4–} layers parallel (101) which are three‐dimensionally interconnected by (K2)⁺ cations.     

Potassium thiocyanate argentates: K3[Ag(SCN)4], K4[Ag2(SCN)6] and K[Ag(SCN)2]

The anions of the title compounds contain [Ag(SCN)₄] units, with the S atoms coordinating to Ag⁺ in a tetrahedral arrangement. Whereas in the isolated anions of tripotassium tetra­thio­cyanatoargentate(I), K₃[Ag(SCN)₄], (I), all SCN^? groups are bonded as terminal ligands, in tetrapotassium di‐μ‐thio­cyanato‐S:S‐bis­[dithio­cyanato­argentate(I)], K₄[Ag₂(SCN)₆], (II), two AgS₄ tetrahedra share one common edge. In poly[potassium [argentate(I)‐di‐μ‐thio­cyanato‐S:S]], K[Ag(SCN)₂], (III), edge‐ and vertex‐sharing of AgS₄ tetrahedra results in infinite [Ag(SCN)₂]^? layers.     

Li2Eu3Br2[BO3]2: A New Europium(II) Halide Oxoborate with Yellow Luminescence

The europium(II) oxoborate Li₂Eu₃Br₂[BO₃]₂ featuring lithium and bromide ions was synthesized by the reaction of Eu₂O₃ with Li[BH₄] as lithium- and boron- as well as EuBr₃ as bromide-source at 750 °C for 24 h in silica-jacketed sealed niobium capsules. The yellow, air-stable and yellow fluorescent compound crystallizes in the trigonal space group R3 m (a = 1049.06(7) pm, c = 2993.1(3) pm, c/a = 2.853, Z = 12). The two crystallographically distinguishable Eu²⁺ cations show either an eightfold coordination as bicapped trigonal prism ([EuO₆Br₂]^12–) or a ninefold coordination as monocapped square antiprism ([EuO₅Br₄]^12–). All oxygen atoms stem from isolated triangular [BO₃]^3– anions and the Li⁺ cations reside in octahedral voids provided by both oxygen atoms and Br^– anions.     

Na3F[WO4]: A Sodium Fluoride Ortho‐Oxotungstate(VI) with Strands of Face‐Shared Fluoride‐Centred Sodium Octahedra According to $^{1}_{\infty}\rm \{[FNa_{6/2}]^{2+}\}$

During the reaction of Na₂[WO₄] with YF₃ purposed to yield fluoride‐derivatized yttrium oxotungstates(VI), colourless platelet‐shaped single crystals of Na₃F[WO₄] emerged as main product. The title compound crystallizes orthorhombically in the space group Pnma (a = 559.59(5), b = 751.02(7), c = 1285.98(9) pm) with four formula units per unit cell. Besides isolated ortho‐oxotungstate units [WO₄]^2? (d(W–O) = 176–178 pm) the crystal structure contains two crystallographically independent Na⁺ cations which are both octahedrally coordinated by four oxygen atoms and two fluoride anions. The F^? anions are surrounded by six sodium cations (d(F–Na) = 224–242 pm) also in an octahedral fashion. These octahedra built up chains along [100] by sharing trans‐oriented faces according to , which are stacked according to a hexagonal closest rod‐packing. The cationic strands are surrounded, interconnected and charge‐balanced by isolated [WO₄]^2? tetrahedra with almost ideal shape and every O^2? ligand is terminally coordinated by three Na⁺ cations.     

Er2S[SiO4]: Ein Erbiumsulfid‐ortho‐Oxosilicat mit ungewöhnlicher Sulfidionen‐Koordination

During the reaction of cadmium sulfide with erbium and sulfur in evacuated silica ampoules pink lath‐shaped crystals of Er₂S[SiO₄] occur as by‐product which were characterized by X‐ray single crystal structure analysis. The title compound crystallizes orthorhombically in the space group Cmce (a = 1070.02(8), b = 1235.48(9), c = 683.64(6) pm) with eight formula units per unit cell. Besides isolated ortho‐oxosilicate units [SiO₄]^4?, the crystal structure contains two crystallographically independent Er³⁺ cations which are both eightfold coordinated by six oxygen and two sulfur atoms. The sulfide anions are surrounded by four erbium cations each in the shape of very distorted tetrahedra. These excentric [SEr₄]¹⁰⁺ tetrahedra build up layers according to by vertex‐ and edge‐connection. They are piled parallel to (010) and separated by the isolated ortho‐oxosilicate tetrahedra.     

Kristallstruktur und magnetische Eigenschaften eines neuen Thiosilicats des Terbiums: Tb4[SiS4]3

Crystal Structure and Magnetic Properties of a New Thiosilicate of Terbium: Tb₄[SiS₄]₃ Terbium thiosilicate Tb₄[SiS₄]₃ was obtained by reaction of the elements in a bromine atmosphere in silica ampoules. The crystal structure was determined by single crystal X—ray diffraction methods (monoclinic, P2₁/n, Z = 4, a = 983.6(2) pm, b = 1096.4(2) pm, c = 1639.1(3) pm, b = 102.76(2)°). The structure is characterized by four crystallographically independent terbium positions with coordination numbers seven and eight as well as isolated [SiS₄]^4—‐tetrahedra. The magnetic behaviour of powdered crystals was interpreted by theoretical calculations where the influence of the crystal field was taken into account by applying the angular overlap model and magnetic exchange by the molecular field approximation.     

Zwei Chloridsilicate des Yttriums: Y3Cl[SiO4]2 und Y6Cl10[Si4O12]

Two Chloride Silicates of Yttrium: Y₃Cl[SiO₄]₂ and Y₆Cl₁₀[Si₄O₁₂] The chloride‐poor yttrium(III) chloride silicate Y₃Cl[SiO₄]₂ crystallizes orthorhombically (a = 685.84(4), b = 1775.23(14), c = 618.65(4) pm; Z = 4) in space group Pnma. Single crystals are obtained by the reaction of Y₂O₃, YCl₃ and SiO₂ in the stoichiometric ratio 4 : 1 : 6 with ten times the molar amount of YCl₃ as flux in evacuated silica tubes (7 d, 1000 °C) as colorless, strongly light‐reflecting platelets, insensitive to air and water. The crystal structure contains isolated orthosilicate units [SiO₄]^4– and comprises cationic layers {(Y2)Cl}²⁺ which are alternatingly piled parallel (010) with anionic double layers {(Y1)₂[SiO₄]₂}^2–. Both crystallographic different Y³⁺ cations exhibit coordination numbers of eight. Y1 is surrounded by one Cl^– and 7 O^2– anions as a distorted trigonal dodecahedron, whereas the coordination polyhedra around Y2 show the shape of bicapped trigonal prisms consisting of 2 Cl^– and 6 O^2– anions. The chloride‐rich chloride silicate Y₆Cl₁₀[Si₄O₁₂] crystallizes monoclinically (a = 1061,46(8), b = 1030,91(6), c = 1156,15(9) pm, β = 103,279(8)°; Z = 2) in space group C2/m. By the reaction of Y₂O₃, YCl₃ and SiO₂ in 2 : 5 : 6‐molar ratio with the double amount of YCl₃ as flux in evacuated silica tubes (7 d, 850 °C), colorless, air‐ and water‐resistant, brittle single crystals emerge as pseudo‐octagonal columns. Here also a layered structure parallel (001) with distinguished cationic double‐layers {(Y2)₅Cl₉}⁶⁺ and anionic layers {(Y1)Cl[Si₄O₁₂]}^6– is present. The latter ones contain discrete cyclo‐tetrasilicate units [Si₄O₁₂]^8– of four cyclically corner‐linked [SiO₄] tetrahedra in all‐ecliptical arrangement. The coordination sphere around (Y1)³⁺ (CN = 8) has the shape of a slightly distorted hexagonal bipyramid comprising 2 Cl^– and 6 O^2– anions. The 5 Cl^– and 2 O^2– anions building the coordination polyhedra around (Y2)³⁺ (CN = 7) form a strongly distorted pentagonal bipyramid.     

Li6+2x[B10Se18]Sex (x ≈ 2), ein ionenleitendes Doppelsalz

Li_6+2x[B₁₀Se₁₈]Se_x (x ≈ 2), an Ion‐conducting Double Salt Li_6+2x[B₁₀Se₁₈]Se_x (x ≈ 2) was prepared in a solid state reaction from lithium selenide, amorphous boron and selenium in evacuated carbon coated silica tubes at a temperature of 800 °C. Subsequent cooling from 600 °C to 300 °C gave amber colored crystals with the following lattice parameters: space group I2/a (at 173 K); a = 17.411(1) Å, b = 21.900(1) Å, c = 17.820(1) Å, β = 101.6(1)°. The crystal structure contains a well‐defined polymeric selenoborate network of composition ([B₁₀Se₁₆Se_4/2]^6?)_n consisting of a system of edge‐sharing [B₁₀Se₁₆Se_4/2] adamantanoid macro‐tetrahedra forming large channels in which a strongly disorderd system of partial occupied Li⁺ cations and additional disordered Se^2? anions is observed. The crystal structure of the novel selenoborate is isotypic to Li_6+2x[B₁₀S₁₈]S_x (x ≈ 2) [1]. X‐ray and ⁷Li magic‐angle spinning NMR data suggest that the site occupancies of the three crystallographically distinct lithium ions exhibit a significant temperature dependence. The lithium ion mobility has been characterized by detailed temperature dependent NMR lineshape and spin‐lattice relaxation measurements.     

Zur Dimorphie von Nd3Cl[SiO4]2

On the Dimorphism of Nd₃Cl[SiO₄]₂ On reacting NdCl₃, Nd₂O₃, and SiO₂ (molar ratio: 1 : 4 : 6) at 850 °C in evacuated silica tubes, pale violet, hydrolysis resistant neodymium(III) chloride ortho‐silicate Nd₃Cl[SiO₄]₂ can be obtained within seven days. If equimolar amounts of NaCl are added as flux, rod‐ or platelet‐shaped, transparent single crystals of two modifications accumulate simultaneously. The one with the higher density (A‐Nd₃Cl[SiO₄]₂) crystallizes monoclinically (C2/c, no. 15; a = 1416.6(1), b = 638.79(6), c = 872.21(9) pm, β = 98.403(7)°; V_m = 117.55 cm³/mol, Z = 4), whereas the one with the lower density (B‐Nd₃Cl[SiO₄]₂) exhibits orthorhombic symmetry (Pnma, no. 62; a = 709.36(7), b = 1815.7(2), c = 631.48(6) pm; V_m = 122.45 cm³/mol, Z = 4). Two crystallographically independent Nd³⁺ cations exist in each of both crystal structures, which in the A type are surrounded by nine (1 Cl^– + 8 O^2–) and ten (2 Cl^– + 8 O^2–), whilst those in the B type by only two times eight (1 Cl^– + 7 O^2– and 2 Cl^– + 6 O^2–) anions, respectively. Thereby all oxygen atoms of both forms represent members of discrete ortho‐silicate tetrahedra ([SiO₄]^4–). Although both crystal structures are built of alternating anionic double layers {(Nd1)₂[SiO₄]₂}^2– and cationic single layers {(Nd2)Cl}²⁺, there is a higher cross‐linkage of the building units in the A‐type lattice, where the cations are coordinated by three and four tetrahedra edges of ortho‐silicate anions, compared to only two times two of them in the B type. From this an about 4% higher density of Nd₃Cl[SiO₄]₂ results for the A‐type structure (D_x = 5.55 g/cm³) in comparison with B‐type Nd₃Cl[SiO₄]₂ (D_x = 5.33 g/cm³).     

La4B14O27: Ein Lanthan‐ultra‐Oxoborat mit Raumnetzstruktur

La₄B₁₄O₂₇: A Lanthanum ultra‐Oxoborate with a Framework Structure Single crystals of La₄B₁₄O₂₇ could be synthesized by the reaction of La₂O₃, LaCl₃ and B₂O₃ with an access of CsCl as fluxing agent in gastightly sealed platinum ampoules within twenty days at 710 °C and appear as colourless, transparent and waterresistant platelets. The new lanthanum oxoborate La₄B₁₄O₂₇ (monoclinic, C2/c; a = 1120.84(9), b = 641.98(6), c = 2537.2(2) pm, β = 100.125(8)°; Z = 4) is built of a three‐dimensional boron‐oxygen framework containing seven crystallographically different boron atoms. Four of these B³⁺ cations are surrounded by four O^2? anions tetrahedrally, whereas the other three have only three oxygen neighbours with nearly plane triangular coordination figures. Three of the [BO₄]^5? tetrahedra form [B₃O₉]^9? rings by cyclic vertex‐condensation, which are further linked via [BO₃]^3? units to infinite layers. Two of these layers connect via one [B₂O₇]^8? unit of two corner‐shared [BO₄]^5? tetrahedra to double layers, which themselves build up a three‐dimensional framework together with chains consisting of two [BO₄]^5? tetrahedra and one [BO₃]^3? triangle. One of the two crystallographically independent La³⁺ cations (La1) is surrounded by ten O^2? anions and resides within the oxoborate double layers. (La2)³⁺ shows a (8+2)‐fold coordination of O^2? anions and occupies channels along the [110] direction.     

Drei Alkalimetall‐Erbium‐Thiophosphate: Von der Schichtstruktur bei KEr[P2S7] zur dreidimensionalen Vernetzung in NaEr[P2S6] und Cs3Er5[PS4]6

Three Alkali‐Metal Erbium Thiophosphates: From the Layered Structure of KEr[P₂S₇] to the Three‐Dimensional Cross‐Linkage in NaEr[P₂S₆] and Cs₃Er₅[PS₄]₆ The three alkali‐metal erbium thiophosphates NaEr[P₂S₆], KEr[P₂S₇], and Cs₃Er₅[PS₄] show a small selection of the broad variety of thiophosphate units: from ortho‐thiophosphate [PS₄]^3? and pyro‐thiophosphate [S₃P–S–PS₃]^4? with phosphorus in the oxidation state +V to the [S₃P–PS₃]^3? anion with a phosphorus‐phosphorus bond (d(P–P) = 221 pm) and tetravalent phosphorus. In spite of all differences, a whole string of structural communities can be shown, in particular for coordination and three‐dimensional linkage as well as for the phosphorus‐sulfur distances (d(P–S) = 200 – 213 pm). So all three compounds exhibit eightfold coordinated Er³⁺ cations and comparably high‐coordinated alkali‐metal cations (CN(Na⁺) = 8, CN(K⁺) = 9+1, and CN(Cs⁺) ≈ 10). NaEr[P₂S₆] crystallizes triclinically ( ; a = 685.72(5), b = 707.86(5), c = 910.98(7) pm, α = 87.423(4), β = 87.635(4), γ = 88.157(4)°; Z = 2) in the shape of rods, as well as monoclinic KEr[P₂S₇] (P2₁/c; a = 950.48(7), b = 1223.06(9), c = 894.21(6) pm, β = 90.132(4)°; Z = 4). The crystal structure of Cs₃Er₅[PS₄] can also be described monoclinically (C2/c; a = 1597.74(11), b = 1295.03(9), c = 2065.26(15) pm, β = 103.278(4)°; Z = 4), but it emerges as irregular bricks. All crystals show the common pale pink colour typical for transparent erbium(III) compounds.     

Rb6LiPr11Cl16[SeO3]12: Ein chloridisch derivatisiertes Rubidium‐Lithium‐Praseodym(III)‐Oxoselenat(IV)

Rb₆LiPr₁₁Cl₁₆[SeO₃]₁₂: A Chloride‐Derivatized Rubidium Lithium Praseodymium(III) Oxoselenate(IV) Transparent green square platelets with often truncated edges and corners of Rb₆LiPr₁₁Cl₁₆[SeO₃]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. Rb₆LiPr₁₁Cl₁₆[SeO₃]₁₂ crystallizes tetragonally in the space group I4/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 Pr³⁺ cations (Pr4) above and below instead, forming square antiprisms of [(Pr4)O₄Cl₄]^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 Pr³⁺. While the Li⁺ cations are surrounded by eight O^2? anions (d(Li?O5) = 251 pm) in the shape of cubes again, the Pr³⁺ 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 Ψ¹‐tetrahedral [SeO₃]^2? anions (d(Se⁴⁺?O^2?) = 169–173 pm) are directing towards the empty cavities between the layer‐connecting [(Pr4)O₄Cl₄]^9? units.     

Crystal Structure of the B‐type Dierbium Oxide ortho‐Oxosilicate Er2O[SiO4]

The crystal structure of B‐type Er₂O[SiO₄] has been determined by single crystal X‐ray diffraction. It crystallizes with the (Mn,Fe)₂[PO₄]F type structure in the monoclinic space group C2/c (a = 14.366(2), b = 6.6976(6), c = 10.3633(16) Å, ß = 122.219(10)°, Z = 8) and shows anionic tetrahedral [SiO₄]^4– units and non‐silicon‐bonded O^2– anions in distorted [OEr₄]¹⁰⁺ tetrahedra. The [(Er1)O₆₊₁] and [(Er2)O₆] polyhedra form infinite chains which are connected by common edges.     

K4VP2S9

The new quaternary group V thio­phosphate K₄VP₂S₉ (tetrapotassium vanadium di­phosphorus nona­sulfide) was prepared by reacting a mixture of K₂S₃, VP, P₄S₃ and S. The crystal structure consists of discrete [VS(PS₄)₂]⁴⁻ anions and K⁺ cations. The V⁴⁺ cation is in a fivefold coordination of S atoms which form a square‐pyramidal environment. Each VS₅ group shares a common edge with two bidentate [PS₄] tetrahedra, yielding the complete anion. The anions are stacked in the direction of the crystallographic b axis and are separated by the K⁺ ions.     

Ce3Cl5[SiO4] und Ce3Cl6[PO4]: Ein chloridreiches Chloridsilicat und ‐phosphat des Cers im Vergleich

Ce₃Cl₅[SiO₄] and Ce₃Cl₆[PO₄]: A Chloride‐Rich Chloride Silicate of Cerium as Compared to the Phosphate By reacting CeCl₃ with CeO₂, cerium and SiO₂, or P₂O₅, respectively, in molar ratios of 5 : 3 : 1 : 3 or 8 : 3 : 1 : 2, respectively, in sealed evacuated silica tubes (7 d, 850 °C) colorless, rod‐shaped single crystals of Ce₃Cl₅[SiO₄] (orthorhombic, Pnma; a = 1619.7(2), b = 415.26(4), 1423.6(1) pm; Z = 4) and Ce₃Cl₆[PO₄] (hexagonal, P6₃/m; a = 1246.36(9), c = 406.93(4) pm; Z = 2) are obtained as products insensitive to air and water. Excess cerium trichloride as flux promotes crystal growth and can be rinsed off again with water after the reaction. The crystal structures are determined by discrete [SiO₄]^4– or [PO₄]^3– tetrahedra as isolated units. Both, the chloride silicate Ce₃Cl₅[SiO₄] and the chloride phosphate Ce₃Cl₆[PO₄], exhibit structural similarities to CeCl₃ (UCl₃ type), when four or three Cl^– anions are each substituted formally by one [SiO₄]^4– or [PO₄]^3– unit, respectively, in the tripled formula (Ce₃Cl₉). The coordination number for Ce³⁺ is thus raised from nine in CeCl₃ to ten in Ce₃Cl₅[SiO₄] and Ce₃Cl₆[PO₄], along with a drastic reduction of the molar volume with the transition from Ce₃Cl₉ (V_m = 186.17 cm³/mol) to Ce₃Cl₅[SiO₄] (V_m = 144.15 cm³/mol) and Ce₃Cl₆[PO₄] (V_m = 164.84 cm³/mol). The polyhedra of coordination around Ce³⁺ can be described as quadruple‐capped trigonal prisms, which in addition to seven Cl^– anions each also show another three oxygen atoms of two ortho‐silicate or ortho‐phosphate tetrahedra, respectively.