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1.
Tiina Maaninen Heikki M. Tuononen Katja Kosunen Raija Oilunkaniemi Johanna Hiitola Risto Laitinen Tristram Chivers 《无机化学与普通化学杂志》2004,630(12):1947-1954
Supermesityl selenium diimide [Se{N(C6H2tBu3‐2, 4, 6)}2; Se{N(mes*)}2] can be prepared in a good yield from the reaction of SeCl4 and (mes*)NHLi. The molecule adopts an unprecedented anti, anti‐conformation, as deduced by DFT calculations at PBE0/TZVP level of theory and supported by 77Se NMR spectroscopy and a crystal structure determination. An analogous reaction involving (C6H2Me3‐2, 4, 6)NHLi [(mes)NHLi] unexpectedly lead to the reduction of selenium and afforded the selenium diamide Se{NH(mes)}2 that was characterized by X‐ray crystallography and 77Se NMR spectroscopy. The Se‐N bonds of 1.847(3) and 1.852(3) Å show normal single bond lengths. The <NSeN bond angle of 109.9(1)° also indicates a tetrahedral AX2E2 bonding arrangement around selenium. Two N‐H···N hydrogen bonds link the Se{NH(mes)}2 molecule with two discrete (mes)NH2 molecules. In the solid state selenium diamide adopts the anti‐conformation, whereas in solution the presence of both syn‐ and anti‐isomers could be observed. PBE0/TZVP calculations of the shielding tensors of 28 different types of selenium‐containing molecules, for which the 77Se chemical shifts are unambiguously known, were carried out to assist the spectral assignment of Se{N(mes*)}2 and Se{NH(mes)}2. 相似文献
2.
Na6Sn4Se11 · 22 H2O can be crystallised at –8 °C as yellow‐orange needles from the 1 : 2 H2O/CH3OH mother liquor of a superheated reaction mixture of NaOH(s), Sn and Se. The bicyclic [Sn4Se11]6– anion exhibits crystallographic C2 symmetry and is composed of corner‐bridged SnSe4 tetrahedra. Two opposite tin atoms of an Sn4Se4 8‐membered ring are linked by a common Se atom, thereby affording two 6‐membered boat‐shaped Sn3Se3 rings with a shared Sn–Se–Sn bridging unit. [Sn4Se11]6– thus represents the immediate precursor of the well‐known adamantane‐like [Sn4Se10]4– anion. 相似文献
3.
Novel Halogenochalcogeno(IV) Acids: [H3O(Benzo‐18‐Crown‐6)]2[Te2Br10] and [H5O2(Dibenzo‐24‐Crown‐8)]2[Te2Br10] Systematic studies on halogenochalcogeno(IV) acids containing tellurium and bromine led to the new crystalline phases [H3O(Benzo‐18‐Crown‐6)]2[Te2Br10] ( 1 ) and [H5O2(Dibenzo‐24‐Crown‐8)]2[Te2Br10] ( 2 ). The [Te2Br10]2‐ anions consists of two edge‐sharing distorted TeBr6 octahedra, the oxonium cations are stabilized by crownether. ( 1 ) crystallizes in the monoclinic space group P21/n with a = 14.520(5) Å, b = 22.259(6) Å, c = 16.053(5) Å, β = 97.76(3)° and Z = 4, whereas ( 2 ) crystallizes in the triclinic space group with a = 11.005(4) Å, b = 12.103(5) Å, c = 14.951(6) Å, α = 71.61(3)°, β = 69.17(3)°, γ = 68.40(3)° and Z = 1. 相似文献
4.
Dark brown crystals of [NnPr4]2[TeBr6(SeBr2)2] ( 1 ) were obtained when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and tetrapropylammonium bromide. The salt 1 crystallizes in the monoclinic space group P21/n with the cell dimensions a = 14.7870(3) Å, b = 9.5523(3) Å, c = 16.7325(3) Å, β = 110.56(10)° (at 123(2) K). In the solid state the [TeBr6(SeBr2)2]2– anion contains a nearly regular [TeBr6] octahedron in which the four equatorial bromo ligands have developed bonds to SeII atoms of the SeBr2 molecules. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are 3.0000(4) and 3.0561(4) Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV–Br distances are in the range 2.6816(3)–2.7131(3) Å and the SeII–Br bond lengths in the coordinated SeBr2 molecules are 2.3548(4) and 2.3725(4) Å. 相似文献
5.
The brown crystals of [PMePh3]2[Se2Br6] ( 1 ) and red crystals of [PMePh3]2[SeBr6(SeBr2)2] ( 2 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of methyltriphenylphosphonium bromide. The crystal structures of 1 and 2 has been determined by the X‐ray methods and refined to R = 0.0373 for 2397 reflections and 0.0397 for 3417 reflections, respectively. The salt 1 crystallizes in the monoclinic space group P21/n with the cell dimensions a = 13.202(5) Å, b = 11.954(4) Å, c = 13.418(6) Å, β = 93.08(4)° (193(2)). The crystals of 2 are triclinic, space group with the cell dimensions a = 10.266(3) Å, b = 11.311(3) Å, c = 11.619(2) Å, α = 108.87(2)°, β = 105.72(2)°, γ = 99.40(2)° (193(2) K). In the solid state structure of 1 the dinuclear hexabromo‐diselenate(II) anion is centrosymmetric and consists of two distorted almost square planar SeBr4 units sharing a common edge through two μ‐bridging Br atoms. The terminal SeII–Br bonds are 2.3984(11) and 2.4273(11) Å, whereas the bridging μBr–SeII bonds are 2.7817(11) and 2.9081(12) Å. In the solid state the trinuclear [SeBr6(SeBr2)2]2? anion of 2 is centrosymmetric too and contains a nearly regular [SeBr6] octahedron where the four equatorial bromo ligands each have developed bonds to the SeII atoms of the SeBr2 molecules. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are 3.0603(15) and 3.1043(12) Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The SeIV–Br distances are in the range 2.5570(9)–2.5773(11) Å and the SeII–Br bond lengths in coordinated SeBr2 molecules – 2.3411(12) and 2.3421(10) Å. 相似文献
6.
Alkali‐metal scandium oxoselenates(IV) ASc[SeO3]2 (A = Na – Cs) are known since a few years and a hydrothermal synthesis was used to obtain them. In our new studies we applied a flux‐supported solid‐state reaction and produced colorless single crystals as well. All representatives ASc[SeO3]2 with A = Na – Cs crystallize in the orthorhombic space group Pnma, in contrast to earlier reports for hexagonal RbSc[SeO3]2. Furthermore we have extended this field with some crystals showing a mixed occupation on the alkali‐metal site, namely (K,Na)Sc[SeO3]2, (Rb,K)Sc[SeO3]2, and (Cs,Rb)Sc[SeO3]2. Since all of them contain [ScO6]9– octahedra and [SeO3]2– ψ1‐tetrahedra the diverse connectivity of the distinct alkali‐metal centered oxygen polyhedra differentiates the compounds with the smaller alkali metals (A′ = Na and K) from those with the bigger ones (A′′ = Rb and Cs). For the mixed crystals the amount of smaller or bigger alkali metal is responsible, which design is chosen by the system. This forces the mixed crystal (Rb,K)Sc[SeO3]2 with a higher amount of potassium instead of rubidium to crystallize isotypically with KSc[SeO3]2 and NaSc[SeO3]2, whereas the pure rubidium compound RbSc[SeO3]2 adopts the CsSc[SeO3]2‐type structure. These findings are supported by single‐crystal Raman spectroscopy. 相似文献
7.
P. S. Berdonosov P. Schmidt O. A. Dityat'yev V. A. Dolgikh P. Lightfoot Michael Ruck 《无机化学与普通化学杂志》2004,630(10):1395-1400
Pale pink crystals of Nd2(SeO3)2(SeO4) · 2H2O were synthesized under hydrothermal conditions from H2SeO3 and Nd2O3 at about 200 °C. X‐ray diffraction on powder and single‐crystals revealed that the compound crystallizes with the monoclinic space group C 2/c (a = 12.276(1) Å, b = 7.0783(5) Å, c = 13.329(1) Å, β = 104.276(7)°). The crystal structure of Nd2(SeO3)2(SeO4) · 2H2O is an ordered variant of the corresponding erbium compound. Eight oxygen atoms coordinate the NdIII atom in the shape of a bi‐capped trigonal prism. The oxygen atoms are part of pyramidal (SeIVO3)2? groups, (SeVIO4)2? tetrahedra and water molecules. The [NdO8] polyhedra share edges to form chains oriented along [010]. The selenate ions link these chains into layers parallel to (001). The layers are interconnected by the selenite ions into a three‐dimensional framework. The dehydration of Nd2(SeO3)2(SeO4) · 2H2O starts at 260 °C. The thermal decomposition into Nd2SeO5, SeO2 and O2 at 680 °C is followed by further loss of SeO2 leaving cubic Nd2O3. 相似文献
8.
Brown crystals of [PPh4]2[Se2Br6] ( 1 ) and [PEtPh3]2[Se2Br6] ( 2 ) were obtained when selenium and bromine reacted in acetonitrile solution in the presence of tetraphenylphosphonium bromide and ethyltriphenylphosphonium bromide, respectively. The crystal structure of 2 has been determined by X‐ray methods and refined to R = 0.0420 for 4161 reflections. The crystals are monoclinic, space group P21/n with Z = 2 and a = 13.055(3) Å, b = 12.628(3) Å, c = 13.530(3) Å, β = 92.40(3)° (293(2) K). In the solid state structure of 2 the dinuclear hexabromo‐diselenate(II) anion is centrosymmetric and consists of two distorted almost square‐planar SeBr4 units sharing a common edge through two bridging Br atoms. The terminal SeII–Br bond distances are found to be 2.419(1) and 2.445(1) Å, the bridging μBr–SeII bond distances 2.901(1) and 2.802(1) Å. 相似文献
9.
Syntheses and X‐Ray Crystal Structures of [Li(thf)4][SnCl5(thf)] and {[Li(Et2O)2]2‐(μ‐Cl2)2‐SnIVCl2}
The syntheses and single crystal X‐ray structure determinations are reported for [Li(thf)4][SnCl5(thf)] ( 1 ) and {[Li(Et2O)2]2‐(μ‐Cl2)2‐SnIVCl2} ( 2 ). Compound 1 is ionic with a tetrahedral coordinated lithium cation and distorted octahedral tin (IV) atom in the anion, while compound ( 2 ) is a centrosymmetric heteronuclear double salt of LiCl and SnCl4. [Li(thf)4][SnCl5(thf)] is monoclinic, P21/n, a = 11.204(1), b = 15.599(1), c = 17.720(2) Å; β = 96.734(2)°, Z = 4, R 0.0418; {[Li(Et2O)2]2‐(μ‐Cl2)2‐SnIVCl2} is monoclinic, P21/n, a = 10.848(2), b = 12.764(2), c = 11.748(2) Å; β = 90.388(3)°, Z = 4, R = 0.0851. 相似文献
10.
Red crystals of [NMeEt3]2n[TeBr6(Se2Br2)3]n ( 1 ) were isolated when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriethylammonium bromide (1:2). The salt 1 crystallizes in the monoclinic space group C2/c with the cell dimensions a = 27.676(6) Å, b = 9.665(2) Å, c = 18.796(4) Å and ß = 124.96(3)° (120 K). The [TeBr6(Se2Br2)3]2— anions contain nearly regular octahedral [TeBr6]2— ions which are incorporated into a polymeric chain by bonding contacts between 3 facial bromo ligands and 3 Se2Br2 molecules, one of which is situated on the twofold symmetry axis. The distances between the μBr ligands and the SeI atoms of the Se2Br2 molecules are observed in the range 3.308(2) — 3.408(2) Å and can tentatively be interpreted as donor‐acceptor bonds with μBr as donors and Se2Br2 as acceptors. The TeIV—Br distances are in the range 2.669(1) — 2.687(1) Å. The bond lengths in the connecting Se2Br2 molecules are: SeI—SeI = 2.267(2) and 2.281(2) Å, SeI—Br = 2.340(1), 2.353(1) and 2.337(1) Å. 相似文献
11.
Colorless platelets of Na2Lu3I3[TeO3]4 were obtained within five days at 775 °C by the reaction of Lu2O3 and TeO2 in a 3:8 molar ratio with NaI added in excess as both fluxing agent and reactant in evacuated silica ampoules. It crystallizes in the monoclinic space group P2/c with the lattice parameters a = 921.69(5), b = 552.71(3), c = 1664.37(9) pm, β = 90.218(4)° and Z = 2. The crystal structure of Na2Lu3I3[TeO3]4 exhibits two crystallographically different Lu3+ cations, both coordinated by eight O2– anions as square antiprisms. These polyhedra are interconnected through four common edges to build up {}^2_∞ {[LuO{}^e_8/2 ]5–} layers (e = edge‐linking) parallel to (100). Furthermore, the crystal structure includes a crystallographically unique Na+ cation surrounded by four O2– and four I– anions also in the shape of a square antiprism. These polyhedra connect via common (I2)–···(I2)– edges in generating {}^1_∞ {[Na2O8I{}^e_4 ]18–} double‐strands that are further linked by (I1)– vertices to result in the formation of {}^2_∞ {[Na2O8I3{}^e,v_3 ]17–} layers (v = vertex‐linking) spreading out parallel to (100) as well. Thus, the crystal structure contains two crystallographically distinct I– anions, of which (I1)– is coordinated nearly linear (? (Na–I1–Na) = 179.6°) by two Na+ cations, whereas (I2)– has contact to three of them displaying a distance of 114 pm from the triangular (Na+)3 plane. The crystal structure of Na2Lu3I3[TeO3]4 is completed by two crystallographically independent Te4+ cations that show stereochemically active non‐bonding electron pairs (“lone pairs”) and are located above and below the {}^2_∞ {[LuO{}^e_8/2 ]5–} layers forming isolated ψ1‐tetrahedral [TeO3]2– anions (d(Te–O) = 188–190 pm) with all oxygen atoms. 相似文献
12.
13.
Zhaofu Fei Holger Thnnessen Peter G. Jones Lindsey Crowe Robin K. Harris Reinhard Schmutzler 《无机化学与普通化学杂志》2000,626(8):1763-1772
The reaction of the bis‐chlorophosphines 1 a – 1 d with bis(2‐chloroethyl)amine hydrochloride in the presence of triethylamine and with various trimethylsilylamines led to a new class of bis‐phosphorus ligands 2 a – 2 c and 3 a – 3 g . 31P‐NMR studies suggested that the bis‐phosphorus ligands undergo rotation reactions about the alkyl bridge in polar solvents. Compounds 2 a – 2 c showed initially only one sharp singlet each in their 31P‐NMR spectra. After a few days at room temperature, two signals were observed. Similar results were observed for 3 a – 3 g . In the solid state, the two phosphorus atoms in 2 c are not equivalent, as was confirmed by the observation of two signals in the solid state 31P‐NMR spectrum. Oxidation reactions of 2 a – 2 c by the hydrogen peroxide‐urea 1 : 1 adduct (NH2)2C(:O) · H2O2 led to the formation of the corresponding phosphoryl compounds 4 a – 4 c . Reaction of 2 a and 3 a with Pt[COD]Cl2 (COD = 1.5‐Cyclooctadiene) furnished the complexes 5 and 6 . The NMR spectra suggested that the two chlorine atoms are in cis position. X‐ray structure analyses were conducted for 2 a , which exhibits twofold symmetry; 2 c , which is linked into dimers by hydrogen bonds C–H…O; and 6 , confirming the cis configuration. 相似文献
14.
Victor N. Khrustalev Ivan A. Portnyagin Nikolay N. Zemlyansky Irina V. Borisova Yuri A. Ustynyuk Mikhail Yu. Antipin Mikhail S. Nechaev Robert West 《应用有机金属化学》2005,19(6):774-777
Germanium(II) dipropionate (1) has been synthesized and its crystal structure, as well as that of germanium(IV) tetrapropionate (2), has been determined. By contrast to monomeric 2 with monodentate propionate ligands, compound 1 is associated, forming a cyclotetramer [Ge(O2CEt)2]4 (1a) via intermolecular dative C?O → Ge interactions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
15.
The donor‐acceptor complexes Et2O·SeO3 and (Me2O)2·SeO3 can be obtained as primary products by the reactions of selenium trioxide with dimethyl ether (Me2O) and diethyl ether (Et2O). The crystal and molecular structure of both complexes, which are stable below their melting points only, was determined by X‐ray structure analysis. Pairs of molecules Et2O·SeO3 form dimers due to two weak intermolecular Se···O contacts. No intermolecular interactions were observed in (Me2O)2·SeO3. Trigonal bipyramidal coordination around SeVI atoms in the latter complex is almost undistorted. Conversion of the adducts to dialkylesters of diselenic and selenic acid in the liquid phase was monitored by Raman, 1H‐ and 77Se‐NMR spectroscopy. 相似文献
16.
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 O2? anions (d(Li?O5) = 251 pm) in the shape of cubes again, the Pr3+ cations are likewisely coordinated by eight O2? anions as square antiprisms (for Pr1, d(Pr1?O2) = 242 pm) and by ten O2? 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+?O2?) = 169–173 pm) are directing towards the empty cavities between the layer‐connecting [(Pr4)O4Cl4]9? units. 相似文献
17.
Brown crystals of [PMePh3]2[TeBr6(SeBr2)2] ( 1 ) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr6(SeBr2)2]2— anion contains a nearly regular [TeBr6] octahedron where the four equatorial bromo ligands each have developed a bond to the SeII atom of a SeBr2 molecule. The contacts between the bridging bromo and the SeII atoms of the SeBr2 molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr2 molecules as acceptors. The TeIV—Br distances are in the range 2.67—2.72Å, and the SeII—Br bond lengths in coordinated SeBr2 molecules in the range 2.33—2.34Å. 相似文献
18.
Single Crystals of the Cerium(IV) Oxotellurate(IV) CeTe2O6 Orange‐red, coffin‐shaped single crystals of CeTe2O6 (monoclinic, P21/n; a = 703.71(5), b = 1106.32(8), c = 735.24(5) pm, β = 108.066(6)°; Z = 4) were obtained by the reaction of admixtures of cerium dioxide and tellurium dioxide (CeO2, TeO2; molar ratio 1 : 2) in the presence of fluxing CsCl (750 °C, 4 d) in evacuated silica tubes. The crystal structure contains eightfold coordinated Ce4+ cations, which are surrounded by irregular trigonal dodecahedra of oxygen atoms. The interconnection of these [CeO8] polyhedra occurs via two edges (O2–O2′ and O3–O3′) with equatorial orientation relative to each other forming zigzag chains {[CeO4/1O4/2]8–} which run parallel to [100] and arrange as a hexagonal packing of rods. Both crystallographically different Te4+ cations exhibit trigonal non‐planar coordination figures (ψ1 tetrahedra) with three oxygen atoms each as a result of the stereochemical activity of the non‐binding electron pairs (“lone pairs”). They also are responsible for the necessary cross‐linkage of the anionic {[CeO6]8–} chains. The isotypical relationship with Ce(SeO3)2 therefore justifies the formulation Ce(TeO3)2 for CeTe2O6. 相似文献
19.
Veysel T. Yilmaz Turan K. Yazicilar Omer Andac Halil Kutuk Yunus Bekdemir William T. A. Harrison 《无机化学与普通化学杂志》2002,628(8):1908-1912
The reaction of sodium benzoxasulfamate (nbs) with cadmium(II) and mercury(II) sulfate in aqueous solution yield the novel complexes [Cd(nbs)2(H2O)4] (1) and [Hg(nbs)2(H2O)3] ( 2 ), respectively. The complexes were characterized by elemental analyses, IR spectroscopy and X‐ray crystallography. Complex 1 is monomeric and has an octahedral arrangement in which the N‐donor nbs ligands occupy the axial positions, while the water oxygen atoms form the equatorial plane. Complex 2 is polymeric and shows a pentagonal bipyramidal arrangement achieved by the bridging of the HgN2O3 units through the weak interaction of the O atoms of the nitro group. The nbs ligands also occupy the axial positions of the pentagonal bipyramid, whereas three water and two nitro oxygen atoms constitute the pentagonal plane. The crystal structure packing in both crystals is achieved by the intermolecular hydrogen bonds involving water hydrogen atoms, nitro and sulfonyl oxygen atoms. 相似文献
20.
Pnictogenidostannates(IV) with Discrete Tetrahedral Anions: New Representatives (E1)4(E2)2[Sn(E15)4] (with E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) of the Na6[ZnO4] Type and the Superstructure Variant of K4Sr2[SnAs4] The silvery to dark metallic lustrous compounds (E1)4(E2)2[Sn(E15)4] (E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) were prepared from melts of stoichiometric mixtures of the elements. They crystallize in the Na6[ZnO4]‐type structure (hexagonal, space group: P63mc, Z = 2; Na4Ca2[SnP4]: a = 938.94(7), c = 710.09(8) pm; K4Sr2[SnAs4]: a = 1045.0(2), c = 767.0(1) pm; K4Ba2[SnP4]: a = 1029.1(6), c = 780.2(4) pm; K4Ba2[SnAs4]: a = 1051.3(1), c = 795.79(7) pm; K4Ba2[SnSb4]: a = 1116.9(2), c = 829.2(1) pm; K4Ba2[SnBi4]: a = 1139.5(2), c = 832.0(2) pm). The anionic partial structure consists of tetrahedra [Sn(E15)4]8– orientated all in the same direction along [001]. In the cationic partial structure one of the two cation positions is occupied statistically by alkali and alkaline earth metal atoms. Up to now only for K4Sr2[SnAs4] a second modification could be isolated, forming a superstructure type with three times the unit cell volume (hexagonal, space group: P63cm, Z = 6; a = 1801.3(2), c = 767.00(9) pm) and an ordered cationic partial structure. 相似文献