Search Results

You are looking at 1 - 10 of 60 items

  • Author: Thomas Schleid x
Clear All Modify Search

Stoichiometric oxidation of SmCl2 with sulfur in the presence of NaCl (evacuated silica vessel, 850 °C, 7 d) results in the formation of A—Sm2S3 (orthorhombic, Pnma (no. 62), a = 737.64(5), b = 397.44(3), c = 1536.26(9) pm, Z = 4, Rw = 0.017). In contrast, C—Sm2S3 (cubic, I43 d (no. 220), a = 844.71(3) pm, Z = 5.333, Rw = 0.017) is obtained upon reaction of the elements (Sm : S = 2 : 3) under otherwise analogous conditions. According to Sm2.670.33S4 it represents a defect-variant of mixed-valence Th3P4-type Sm3S4 (a = 852.39(3) pm, Z = 4, Rw = 0.013) which forms whenever reducing tantalum is used as container material instead of silica tubing. Ubiquitous oxidic impurities thereby also react to yield the oxygen-poor oxysulfides Sm10S14O (tetragonal, 141/acd (no. 142), a = 1485.96(4), c = 1974.04(8), Z = 8) and Sm2OS2 (monoclinic, P21/c (no. 14), a = 840.54(6), b = 706.20(5), c = 697.72(5) pm, β = 99.294(6)°, Ζ = 4, Rw = 0.024) as by-products. Regardless of the container material, NaCltype SmS (cubic, Fm 3 m (no. 225), a = 596.04(3) pm, Z = 4) emerges as product from equimolar oxidation of samarium with sulfur. Reactions of Sm2S3 with Sm2O3 in 1: 2 molar ratios are suitable to produce Ce2O2S-type Sm2O2S (trigonal, P 3 ml (no. 164), a = 389.25(3), c = 671.18(7) pm, Z = 1) even in tantalum capsules at 850 °C when some NaCl is added as a flux.

The oxidation of reduced chlorides (MCl2) or chloride-hydrides (MClHx) of the lanthanides with sulfur (700-850 °C, 7 d, sealed tantalum capsules or evacuated silica vessels) usually results in the formation of the sesquisulfides M2S3 as the main products. In the presence of appropriate fluxes (e.g., alkali halides), the products often are obtained as single crystals, and the flux decides which modification is favoured. Ternary halides of the trivalent lanthanides with the corresponding alkali metal can mostly be found as the second components. Crystal growth and structural investigations of thus produced single crystals of Pr2S3 (from PrClH0.67 + S + NaCl, 5:5:1, A type: orthorhombic, Pnma (No. 62), Z = 4, a = 748.22(5), b = 405.51(3), c = 1560.74(9) pm, R = 0.024, Rw = 0.020), Ho2S3, (from U - Ho2S3, + KI, 1:1, D type: monoclinic, P21/m (No. 12), Z = 6, a = 1746.15(9), b = 400.23(3), c = 1012.43(6) pm, β = 98.529(4)°, R = 0.041, Rw = 0.035), and Yb2S3 (from T-Yb2S3 + KI, 1:1, E type: trigonal, R3̄c (No. 167), Z = 6, a = 674.97(2), c = 1820.11(9) pm, R = 0.019, Rw = 0.018) are reported here. In accordance with the lanthanide contraction, the trivalent cations (M3+) exhibit sulfur coordination numbers of 7 and 8 in A -Pr2S3, 6 and 7 in D -Ho2S3, and 6 in E -Yb2S3 (corundum-type structure).

Colourless single crystals of [Eu(CH3COO)2(H2O)3]Cl are obtained at about 5°C from a solution of EuCl3 · 6 H2O in a mixture of acetone, tetrahydrofurane and acetanhydride (1:1:2) to which a small amount of water had been added. [Eu(CH3COO)2(H2O)3]Cl crystallizes in the monoclinic system, space group P21/n (No. 14), a = 786.19(5), b = 791.86(5), c = 1768.81(13) pm; β = 98.235(6)°, R = 0.025, Rw = 0.021, Z = 4. Eu3+ is in nine-coordinate surrounding of O2-, three of which belong to water molecules and six to acetate anions (two bidentate and two monodentate). Cationic chains of the composition [Eu(CH3COO)2(H2O)3]+ are formed through further connection via acetate-oxygen atoms. These chains are stacked hexagonally parallel [100] and held together by “lonesome” Cl- anions. The chloride ions are surrounded by 4+1 aquo ligands.

Abstract

Oxysulfide chlorides, M4OS4Cl2, of the lanthanides (M = La - Nd) are obtained upon the oxidation of the metals with sulfur in the presence of MOCl (or M2O3) and MCl3 in appropriate molar ratios. Additional NaCl or an excess of MCl3 serving as a flux provide even single crystalline material after reactions at 850 °C for seven days in sealed tantalum capsules. The crystal structure of M4OS4Cl2 (hexagonal, P63mc, no. 186, Z = 2; M = La: a = 933.19(3), c = 701.22(4) pm, c/a = 0.7514, R = RH = 0.020; M = Ce: a = 925.49(3), c = 694.13(3) pm, c/a = 0.7500; M = Pr: a = 919.72(4), c = 688.53(4) pm, c/a = 0.7486; M = Nd: a = 914.25(4), c = 683.12(4) pm, c/a = 0.7472, R = 0.022, Rw = 0.019) contains isolated O2--centered (M3+)4 tetrahedra which are surrounded by twelve S2- and six Cl-, capping vertices, edges, and faces of each tetrahedron and linking to other [OM4] units. Basically, the structure is identical to that of Ba4OCl6 if Ba2+ is substituted by M3+ and 2/3 of the CL- anions are replaced by S2- to secure charge neutrality in M4OS4Cl2. Different models for the Cl-/S2- replacement are presented on the basis of comparisons of the Madelung part of the lattice energy (MAPLE) with the MAPLE sum of the binaries (M2O3, M2S3, and MCl3).

Abstract

The lanthanoid chalcogenide ortho-oxosilicates M4.667Ch[SiO4]3 (M = Nd, Sm; Ch = O, S) with apatite-type crystal structure have been synthesized by the reaction of either M2O3 and SiO2 or M2O3, M, S and SiO2 using CsCl as flux in evacuated silica tubes at 850 °C for 7d. The title compounds crystallize hexagonally in the space group P63 /m with two formula units per unit cell. Their crystal structure contains two crystallographically independent lanthanoid cations, of which (M1) is surrounded by nine O ligands in the shape of a tricapped trigonal prism. Additionally, this site is only occupied by 81–84% to assure that the composition is electroneutral. The (M2) cations have an environment of seven O anions in the case of M4.667O[SiO4]3, which form a pentagonal bipyramid. Considering M4.667S[SiO4]3 this polyhedron changes, when one of the apical oxide particles is substituted by two sulfide ligands which then form a “two-legged” pentagonal bipyramid. Both the non-silicon bonded oxygen in the oxide derivative and the sulfur in the sulfide homologue are situated in a channel along [001]. While oxygen prefers a trigonal planar cationic coordination at the Wyckoff position 2a (CN = 3), the sulfur represents the centre of a trigonal antiprism at the Wyckoff position 2b (CN = 6).

Abstract

Transition metal(II) decahydro-closo-decaborate hydrates [M(H2O)6][B10H10] · 2H2O (M = Fe, Co, Ni) were synthesized by reacting an aqueous solution of (H3O)2[B10H10] with the corresponding metal powders. The manganese(II) compound [Mn(H2O)6][B10H10] · 2H2O could be obtained by the reaction of an aqueous solution of Ba[B10H10] with Mn(SO4) · H2O after the precipitation of Ba(SO4). For the zinc salt [Zn(H2O)6][B10H10] · 2H2O an aqueous solution of (H3O)2[B10H10] was reacted with the basic zinc(II) carbonate [Zn(CO3)]2 · [Zn(OH)2]3. All five compounds crystallize isotypically in the monoclinic space group C2/c with four formula units per unit cell. Their crystal structure contains crystallographically unique transition metal(II) cations, which are octahedrally coordinated by oxygen atoms of six water molecules. Another six water molecules are bound to each hexaaqua-transitionmetal( II) cation through hydrogen bonds, again erecting a distorted octahedron. The second octahedra are linked to each others via common edges to build up a layer containing [M(H2O)6]2+ cations and second-sphere crystal water molecules. Between these layers the bicapped square-antiprismatically shaped decahydro-closo-decaborate anions [B10H10]2- are situated and held there through non-classical hydrogen bonds between the positively polarized hydrogen atoms of water molecules and the negatively polarized hydrogen atoms of boron-cluster anions. The closo-decaborate clusters themselves show only slight distortions away from their ideal D4d symmetry as vibrational spectroscopy studies prove. Stepwise thermal decomposition takes place not only under water removement, but finally also under hydrogen evolution.

Orthorhombic single crystals of CsCu3Dy2S5 (a = 397.54(4), b = 1414.8(1), c = 1685.7(2) pm) and CsCu3Er2S5 (a = 394.82(4), b= 1410.9(1), c = 1667.2(2) pm; both Cmcm, Z = 4) are obtained as by-products (pale yellow or pink transparent needles) in attempts to synthesize CuMS2 (M = Dy and Er) through the oxidation of elemental copper, dysprosium and erbium, respectively, with sulfur (molar ratios: 1:1:2 ) in the presence of equimolar amounts of cesium chloride (CsCl) as fluxing agent at 900 °C within fourteen days from torch-sealed evacuated silica tubes. Their crystal structure contains octahedral [MS6]9- units (d(M-S) = 269 - 282 pm) which share edges and vertices to form layers 2 {(M2S5)4-} parallel (010). These are three-dimensionally interconnected along [010] by two crystallographically different Cu+ cations in tetrahedral coordination of S2- anions (d(Cu-S) = 227 - 269 pm) according to 3 {(Cu3M2S5)- }. Thereby a likewise layered substructure 2 {(Cu3S5)7-} is formed parallel (010) by edge- and vertexlinking of all [CuS4]7- tetrahedra. Large channels within the 3 {(Cu3M2S5)-} network spread along [100] and suit well to take up the highly coordinated Cs+ cations, which are surrounded by eight plus one S2- anions at distances between 340 and 358 pm (8x) with the ninth ligand 420 - 421 pm apart in the shape of (2+1)-fold capped trigonal prisms.

Pale violet, plate-like single crystals of the title compound, neodymium(III) oxide chloride oxotellurate( IV) Nd5O4Cl3[TeO3]2, can be obtained by the reaction of Nd2O3 with NdCl3 and TeO2 in equimolar ratios in evacuated silica ampoules within five days at 775 °C with an excess of CsCl added as fluxing agent. Nd5O4Cl3[TeO3]2 crystallizes in the monoclinic space group C2/m (no. 12) with the lattice parameters a = 1270.61(9), b = 562.70(4), c = 1008.97(8) pm, β = 90.784(3)°and Z = 2, and is thus isostructural to the lanthanoid(III) oxide halide oxoselenates(IV) Tb5O4Cl3[SeO3]2 and Gd5O4Br3[SeO3]2. The crystal structure exhibits three crystallographically different Nd3+ cations, of which (Nd1)3+ has a purely oxidic coordination sphere of eight oxide anions building up a square prism. (Nd2)3+ and (Nd3)3+ are both coordinated by oxide and chloride anions. The coordination polyhedron around (Nd2)3+ is a trigonal prism of oxide anions that is capped by one chloride anion to give a coordination number of seven. (Nd3)3+ resides in an eightfold coordination of five oxide and three chloride anions forming a square antiprism. All (O1)2 anions are surrounded tetrahedrally by Nd3+ cations as [ONd4]10+ units. These tetrahedra share common edges and vertices to generate two-dimensional infinite layers of the composition 2 {[O4Nd5]7+ }, which extend parallel to the (001) plane. The chloride anions (Cl1)are connecting those slabs via Nd3-Cl1-Nd3 bridges along the [001] direction, while the (Cl2)anions alternate with the Te4+ cations above and below the layers. The three-dimensional crystal structure of Nd5O4Cl3[TeO3]2 is completed by Te4+ cations, which are bonded to one (O2)2 and two (O3)2 anions to form ψ1-tetrahedra [TeO3]2 with a nonbinding, stereochemically active electron pair (“lone pair”) pointing into the free space between the chloride-decorated 2 {[O4Nd5]7+ } layers

YF[SeO3]-type rare-earth metal(III) fluoride oxoselenates(IV) MF[SeO3] (M = Y, Ho-Lu) crystallize monoclinically in space group P21/c (no. 14) with Z = 4. Obeying the lanthanoid contraction, the lattice parameters decrease successively from a = 657.65(7), b = 689.71(7), c = 717.28(7) pm and β = 99.036(5)° for YF[SeO3] at 298 K to a = 648.39(6), b = 681.28(7), c = 705.81(7) pm and β = 98.657(5)° for LuF[SeO3] at 100 K (LT-LuF[SeO3], LT ≡ Low Temperature). The M3+ cations are occupying the general site 4e. Contrary to the triclinic structure of RT-LuF[SeO3] (RT ≡ Room Temperature; CN(Lu3+) = 7) the higher coordination number eight is achieved for the M3+ cations in all YF[SeO3]-type compounds. This results in [MO6F2]11− polyhedra (d(M-O) = 228 - 243/225 - 239 plus 263/258 pm, d(M-F) = 219/216 pm, M = Y/Lu), which are connected via common O・ ・ ・O edges to form infinite chains 1 {[MOe 4/2Ot 2/1Ft 2/1]7−} (e ≡ edge-sharing, t ≡ terminal) running along [010]. Neighboring chains share common O3・ ・ ・O3 and O3・ ・ ・F edges generating 2 {[M(O3)3/3(O2)2/2(O1)1/1F2/2]4−} sheets parallel to the (100) plane. Finally, these 2 {[MO3F]4−} sheets are interconnected by Se4+ cations, which appear in isolated ψ1-tetrahedral [SeO3]2− anions (d(Se-O) = 167 - 175 pm). For the synthesis of the YF[SeO3]-type rare-earth metal(III) fluoride oxoselenates( IV) MF[SeO3] (M = Y, Ho-Lu), the rare-earth metal sesquioxides (M2O3) and trifluorides (MF3), and selenium dioxide (SeO2) in molar ratios of 1 : 1 : 3 with the fluxing agent CsBr were reacted within five days at 700 - 750 °C in evacuated graphitized silica ampoules.

In the quaternary system Cs / Nd / Si / O, two new representatives, the phyllo-oxosilicate Cs3NdSi8O19 and the tecto-oxosilicate Cs6Nd2Si21O48, were synthesized by CsF-flux-supported solid-state reactions between Nd2O3 and SiO2. The first one, Cs3NdSi8O19 (orthorhombic, Cmcm (no. 63), a = 705.74(5), b = 2712.85(19), c = 1163.72(8) pm, Z = 4), is not isotypic to the related scandium compound Cs3ScSi8O19. The [SiO4]4− tetrahedra (d(Si4+ -O2−) = 156 -163 pm) in the structure of Cs3NdSi8O19 are connected via common corners to form corrugated, loop-branched double layers containing four- and eight-membered rings in the (010) plane and eight-membered rings along [001]. Each of the eight-membered ellipses emerging along [100] is additionally loopbranched by two four-membered chains. The oxosilicate double layers are cross-linked by vertexsharing via otherwise isolated [NdO6]9− octahedra (d(Nd3+-O2-)= 232 - 234 pm) to build up a three-dimensional framework. Also in between the oxosilicate double layers, the (Cs1)+ cations are located on the 8 f site. Each of the octagonal channels along [001] hosts one (Cs3)+ and two (Cs2)+ cations, which both reside at only partially occupied sites (8g and 8 f , respectively) and disorder, because otherwise too short Cs+ ・ ・ ・ Cs+ distances would occur. The second compound, Cs6Nd2Si21O48, crystallizes also in an orthorhombic space group (Pmmn (no. 59), a = 2189.24(15), b = 731.92(5), c = 1593.61(11) pm, Z = 2). Starting from a loop-branched single layer containing five- and eight-membered rings, a three-dimensional framework of vertex-shared [SiO4]4− tetrahedra (d(Si4+-O2−) = 149 - 164 pm) built up, in which the Si-O distances range from 149 to 164 pm within a broad range. In certain cavities, one kind of Nd3+, but four kinds of Cs+ cations (here, all sites with full occupation) are embedded. Also surrounded by only six O2− anions just like in the first case, the Nd3+ cations (d(Nd3+-O2−) = 233 - 237 pm) exhibit an unusually small, but not unknown coordination sphere for this relatively large lanthanoid(III) cation