Röntgenographische und schwingungsspektroskopische Untersuchungen an wasserfreien Chloraten und Bromaten des Strontiums,Bariums und Bleis. Kristallstruktur des Sr(ClO3)2 und Sr(BrO3)2

X-ray, I.R., and Raman Studies of the Anhydrous Chlorates and Bromates of Strontium, Braium, and Lead. Crystal Structure of Sr(ClO₃)₂ and Sr(BrO₃)₂ . Single crystals of the hitherto badly characterized anhydrous halates Sr(ClO₃)₂, Sr(BrO₃)₂, Ba(BrO₃)₂, Pb(ClO₃)₂, and Pb(BrO₃)₂ have been obtained by crystallization from an aqueous solution or by heating aqueous suspensions of the corresponding monohydrates to 95, 185, 130, and 105°C, respectively, in a vacuum. The halates crystallize in the orthorhombic space group Fdd2–C (Z = 8) with the exception of Sr(BrO₃)₂, which is distorted to the monoclinic space group Cc? C (Z = 4). The crystal structure of Sr(ClO₃)₂ and Sr(BrO₃)₂ have been determined using single crystal X-ray diffraction data. In both compounds, distorted SrO₈ dodecahedra (bisphenoids) are connected to a four-connected three-dimensional net. The ClO ions and one of the two crystallographically non-equivalent BrO ions are strongly distorted. The structures of these compounds and those of Ba(IO₃)₂ and of Ba(ClO₃)₂ · 1 H₂O type compounds are related to a hypothetical AB₂ structure with diamond like arrangement of the metal ions of the common super group Fddd–D. The results of i.r. and Raman spectroscopic measurements are reported and discussed in terms of the crystal structures.     

Kristallstrukturen des Sr(OH)2 · H2O,Ba(OH)2 · H2O (o.-rh. und mon.) und Ba(OH)2 · 3 H2O

Crystal Structures of Sr(OH)₂ · H₂O, Ba(OH)₂ · H₂O (o.-rh. and mon.), and Ba(OH)₂ · 3 H₂O The crystal structures of Ba(OH)₂ · 3 H₂O (Pnma, Z = 4), γ-Ba(OH)₂ · H₂O (P2₁/m, Z = 2) and the isotypic Sr(OH)₂ · H₂O and β-Ba(OH)₂ · H₂O (Pmc2₁, Z = 2) were determined using X-ray single crystal data. Ba(OH)₂ · 3 H₂O and Ba(OH)₂ · H₂O mon. crystallize in hitherto unknown structure types. The structure of Ba(OH)₂ · H₂O mon. is strongly related to that of rare earth hydroxides M(OH)₃ with space group P6₃/m (super group of P2₁/m). The metal-oxygen distances are significantly shorter for OH^? ions (mean Ba—O bond lengths of all hydroxides under investigation 278.1 pm) than for H₂O molecules (289.9 pm). Corresponding to other hydrates of ionic hydroxides, the water molecules form strong hydrogen bonds to adjacent OH^? ions whereas the hydroxide are not H-bonded.     

Competitive Coordination of the Uranyl ion by Perchlorate and Water – The Crystal Structures of UO2(ClO4)2·3H2O and UO2(ClO4)2·5H2O and a Redetermination of UO2(ClO4)2·7H2O (Z. Anorg. Allg. Chem. 2003, 629, 1012–1016)

In the article “Competitive Coordination of the Uranyl ion by Perchlorate and Water – The Crystal Structures of UO₂(ClO₄)₂·3H₂O and UO₂(ClO₄)₂·5H₂O and a Redetermination of UO₂(ClO₄)₂·7H₂O” (Z. Anorg. Allg. Chem. 2003 , 629, 1012–1016), some wrong parameters and bond lengths for UO₂(ClO₄)₂·7H₂O were given in table 1 and table 3 The correct parameters are: a = 1449.5(2) pm, b = 921.6(1) pm, c = 1067.5(2) pm, V = 1422.5(4)·10⁶ pm³, ρ = 2.712 g·cm^?3, μ = 119 cm^?1. The corrected bond lengths for this structure are U–O(1) 175.8(5) pm, U–O(2) 239.1(5) pm, U–O(3) 240.8(5), U–O(4) 242.0(7). A cif file with the correct data has been deposited with the ICSD.     

Magnesiumiodatdecahydrat Mg(IO3)2 · 10 H2O – Kristallstruktur,Ramanspektren, thermischer Abbau,lone-pair-Radius von Iod(V)

Magnesium Iodate Decahydrate Mg(IO₃)₂ · 10 H₂O – Crystal Structure, Raman Spectra, Thermal Decomposition, Lone-Pair Radius of Iodine(V) Mg(IO₃)₂ · 10 H₂O crystallizes in the triclinic space group P1 (a = 654.25(9), b = 1109.8(2), c = 1176.7(2) pm; α = 105.470(8), β = 104.086(8), γ = 101.744(8)°; Z = 2). The structure has been determined by single-crystal X-ray diffraction at 273 K, and refined to a final R value of 0.0272 for 4372 observed reflections (I > 2σ(I)). The magnesium ions are coordinated to six different H₂O molecules forming a slightly distorted octahedron with Mg? O distances varying between 202.2(2) and 211.6(3) pm. The hexaaquamagnesium ions are arranged parallel to (010). The two kinds of iodate ions and the four different “free” water molecules are filled between the layers thus formed. There are twenty independent hydrogen bonds with O … O distances from 268.7(3) to 287.6(4) pm. On the basis of all intermolecular I … I distances of iodates reported in the literature, 180 pm are recommended as van-der-Waals radius resp. lonepair radius of iodine(V). DSC and Raman spectroscopic experiments as well as high-temperature Raman and X-ray measurements were performed and are discussed with respect to the energetic and geometric distortion of the IO₃^? ions and the dehydration of the decahydrate via the tetrahydrate (308 K) to Mg(IO₃)₂ (428 K).     

NiH3IO6 · 6H2O — Kristallstruktur und Schwingungsspektren

NiH₃IO₆ · 6 H₂O — Crystal Structures and Vibrational Spectra The crystal structure of NiH₃IO₆ · 6 H₂O has been determined by X-ray single-crystal diffraction (Pc, Z = 2, a = 516.74(9), b = 981.5(2), c = 1052.5(2) pm, β = 116.496(8)°) on the basis of 4169 unique reflections (R = 1.96%). The structure is built up of distorted Ni(H₂O)₆²⁺ and H₃IO₆^2? octahedra linked by hydrogen bonding. IR and Raman spectra of both the title compound and isostructural MgH₃IO₆ · 6 H₂O as well as of deuterated specimens are given. There are up to 14 different OH(OD) modes in the spectra of isotopically dilute samples due to the 15 different hydrogen positions of the structure. The internal modes of the meridional H₃IO₆^2? ions (pseudo C_2v symmetry) are discussed with respect to that double T-shaped entity, which gives rise to only two instead of 3I? O, I? O(H), and OH stretches in the IR and Raman spectra, i.e. the same as for facial (C_3v) structured ions.     

Zur Kristallstruktur von SrZn(OH)4 · H2O

Crystal Structure of SrZn(OH)₄ · H₂O Colorless crystals of SrZn(OH)₄ · H₂O are obtained by electrochemical oxidation of Zn in a zinc/iron pair in an aqueous ammonia solution saturated with strontium hydroxide. The X-ray crystal structure determination was now successful including all hydrogen positions: P1 , Z = 2, a = 6.244(1) Å, b = 6.3000(8) Å, c = 7.701(1) Å, α = 90.59(1)°, β = 112.56(2)°, γ = 108.66(2)°, N(F ≥ 3σF) = 1967, N(Var.) = 84, R/R_w = 0.020/0.024. In SrZn(OH)₄ · H₂O Zn²⁺ is tetrahedrally coordinated by four OH^? -ions while Sr²⁺ has 6 OH^? and one H₂O as neighbours. The polyhedra around Sr²⁺ are connected to chains which are linked three-dimensionally by isolated tetrahedra [Zn(OH)₄]. Hydrogen bonds between H₂O as donor and OH^? are characterized by raman spectroscopy.     

Barium chlorite hydrate,Ba(ClO2)2·3.5H2O

The structure of barium chlorite hydrate, Ba(ClO₂)₂·3.5H₂O, has been determined by single‐crystal X‐ray analysis at 150 K. The structure is monoclinic, space group C2/c, with Z = 8. It contains layers of Ba²⁺ cations coordinated by ClO₂⁻ anions and water mol­ecules. There are also solvate water mol­ecules involved only in hydrogen bonding of the layers. Three solvate water O atoms are on sites of twofold symmetry, while all other atoms are in general positions. The full coordination environment of the Ba²⁺ cation consists of ten O atoms belonging to six chlorites and three water mol­ecules, forming a bicapped square antiprism.     

IR- und Raman-Spektren der isotypen Iodathydrate M(IO3)2 · 4 H2O (M = Mg,Ni, Co); Kristallstruktur von Co(IO3)2 · 4 H2O

Infrared and Raman Spectroscopy of the Isostructural Iodate Hydrates M(IO₃)₂ · 4 H₂O (M = Mg, Ni, Co)-Crystal Structure of Cobalt Iodate Tetrahydrate The iodate tetrahydrates Mg(IO₃)₂ · 4 H₂O, β-Ni(IO₃)₂ · 4 H₂O, Co(IO₃)₂ · 4 H₂O and their deuterated specimens were studied by X-ray, infrared and Raman spectroscopic methods. The title compounds are isostructural crystallising in the monoclinic space group P2₁/c (Z = 2). The crystal structure of Co(IO₃)₂ · 4 H₂O (a = 836.8(5), b = 656.2(3), c = 850.2(5) pm and β = 100.12(5)°) has been refined by single-crystal X-ray methods (R_obs = 3.08%, 693 unique reflections I₀ > 2σ(I)). Isolated Co(IO₃)₂(H₂O)₄ octahedra form layers parallel (100). Within these layers, the two crystallographically different hydrate water molecules form nearly linear hydrogen bonds to adjacent IO₃^– ions (ν_OD of matrix isolated HDO of Co(IO₃)₂ · 4 H₂O (isotopically diluted samples) 2443 (H3), 2430 (H2), and 2379 cm^–1 (H1 and H4), –180 °C). Intramolecular O–H and intermolecular H…O distances were derived from the novel ν_OD vs. r_OH and the traditional ν_OD vs. r_H…O correlation curves, respectively. The internal modes of the iodate ions of the title compounds are discussed with respect to their coupling with the librations of the hydrate H₂O molecules, the distortion of the IO₃^– ions, and the influence of the lattice potential.     

Röntgenographische und spektroskopische Untersuchungen an Ba2Ni(N3)6· 3H2O

Preparation and X-Ray Examination of Ba₂Ni(N₃)₆ · 3 H₂O Ba₂Ni(N₃)₆ · 3 H₂O has been prepared by the reaction of an aqueous solution of Ba(N₃)₂ with basic nickel azide. The crystals are green, the lattice constants are: a = 7.09 Å, b = 7.09 Å, c = 16.30 Å, α = 74.58°, β = 105.42°, γ = 97.10°, N = 2. Optical spectra point to an octahedral microsymmetry of the azide ions around nickel.     

Zinkiodate – Schwingungsspektren (IR,Raman) und Kristallstruktur von Zn(IO3)2 · 2 H2O

Zinc Iodates – Infrared and Raman Spectra, Crystal Structure of Zn(IO₃)₂ · 2 H₂O The zinc iodates Zn(IO₃)₂ · 2 H₂O and Zn(IO₃)₂ as well as α‐Co(IO₃)₂ · 2 H₂O were studied by X‐ray, IR‐ and Raman spectroscopic methods. The crystal structure of the dihydrate, which is isostructural with the respective cobalt compound, was determined by X‐ray single‐crystal studies (space group P1, Z = 2, a = 490,60(4), b = 667,31(5), c = 1088,85(9) pm, α = 98,855(6), β = 91,119(7), and γ = 92,841(6)°, R1 = 2,55%, 2639 unique reflections I > 2σ(I)). Transconfigurated Zn(IO₃)₄(H₂O)₂ octahedra are threedimensionally connected via common IO₃^– ions parallel to [001] and hydrogen bonds parallel to [100] and [010], respectively. Anhydrous Zn(IO₃)₂ crystallizes in space group P2₁ (Z = 2) with a = 548,9(2), b = 512,4(1), c = 941,8(2) pm, and β = 90,5(3)°. The structure of Zn(IO₃)₂ is a monoclinically distorted variant of the structures of β‐Ni(IO₃)₂ (space group P6₃) and Co(IO₃)₂ (P3). The O–H … O–IO₂ hydrogen bonds of the crystallographically different H₂O molecules of the dihydrates (ν_OD (OD stretching modes of isotopically dilute samples) 2430, 2415, 2333 and 2300 cm^–1, Zn(IO₃)₂ · 2 H₂O, 90 K) are examples to the matter of fact that O … O distances are only a bad measure for the strength of hydrogen bonds. The infrared and Raman spectra as well as a group theoretical treatment are presented and discussed with respect to mutual exclusion principle (possible space groups), the strength of the hydrogen bonds and the distortion of the IO₃^– ions at the C₁ lattice sites.     

Zur Kristallstruktur von CaZn2(OH)6 · 2 H2O

Crystal Structure of CaZn₂(OH)₆ · 2 H₂O The electrochemical oxidation of zinc in a zinc/iron-pair leads in an aqueous NH₃ solution of calciumhydroxide at room temperature to colourless crystals of CaZn₂(OH)₆ · 2 H₂O. The X-ray structure determination was now successful including all hydrogen positions. P2₁/c, Z = 2, a = 6.372(1) Å, b = 10.940(2) Å, c = 5.749(2) Å, β = 101.94(2)° N(F ≥ 3σF) = 809, N(Var.) = 69, R/R_W = 0.011/0.012 The compound CaZn₂(OH)₆ · 2H₂O contains Zn²⁺ in tetrahedral coordination by OH^? and Ca²⁺ in octahedral coordination by four OH^? and two H₂O. The tetrahedra around Zn²⁺ form corner sharing chains, three-dimensionally linked by isolated polyhedra around Ca²⁺. Weak hydrogen bridge bonds result between H₂O as donor and OH^?.     

Synthesis,Crystal Structure,and Thermal Behavior of Pr(ClO3)3 · 2 H2O

Single crystals of Pr(ClO₃)₃ · 2 H₂O have been obtained from the reaction of Pr₂(CO₃)₃ · x H₂O and HClO₃. The crystal structure (orthorhombic, P2₁2₁2₁, Z = 4, a = 576.03(7), b = 1236.7(2), c = 1314.0(2) pm) contains Pr³⁺ ions coordinated by two H₂O molecules and seven ClO₃^– groups. According to DTA/TG measurements, Pr(ClO₃)₃ · 2 H₂O decomposes in a two step mechanism with Pr(ClO₃)₃ as an intermediate and PrOCl as the final product. The decomposition has also been investigated by means of temperature dependent X-ray powder diffraction.     

Über die Alkaliselenoarsenate(III) KAsSe3 · H2O,RbAsSe3 · 1/2 H2O und CsAsSe3 · 1/2 H2O

On the Alkali Selenoarsenates(III) KAsSe₃ · H₂O, RbAsSe₃ · 1/2 H₂O, and CsAsSe₃ · 1/2 H₂O The alkali selenoarsenates(III) KAsSe₃ · H₂O, RbAsSe₃ · 1/2 H₂O, and CsAsSe₃ · 1/2 H₂O have been prepared by hydrothermal reaction of the respective alkali carbonate with As₂Se₃ at a temperature of 135°C. Their X-ray structural analyses demonstrated that the compounds contain polyselenoarsenate(III) anions (AsSe₃^?)_n, in wich the basic units are ψ-AsSe₃ tetrahedra, which are linked together through Se? Se bonds into infinite zweier single chains. The Rb and Cs salts are isotypic.     

Hydrothermal Synthesis of Rare Earth Iodates from the Corresponding Periodates: Structures of Sc(IO3)3, Y(IO3)3 · 2 H2O,La(IO3)3 · 1/2 H2O and Lu(IO3)3 · 2 H2O

Hydrothermal syntheses of single crystals of rare earth iodates, by decomposition of the corresponding periodate, are presented. This appears to be a generic method for making rare earth iodate crystals in a short period of time. Single crystal X‐ray diffraction structures of the four title compounds are presented. Sc(IO₃)₃: Space group R3, Z = 6, lattice dimensions at 100 K; a = b = 9.738(1), c = 13.938(1) Å; R₁ = 0.0383. Y(IO₃)₃ · 2 H₂O: Space group P1, Z = 2, lattice dimensions at 100 K: a = 7.3529(2), b = 10.5112(4), c = 7.0282(2) Å, α = 105.177(1)°, β = 109.814(1)°, γ = 95.179(1)°; R₁ = 0.0421. La(IO₃)₃ · ? H₂O: Space group Pn, Z = 2, lattice dimensions at 100 K: a = 7.219(2), b = 11.139(4), c = 10.708(3) Å, β = 91.86(1)°; R₁ = 0.0733. Lu(IO₃)₃ · 2 H₂O: Space group P1, Z = 2, lattice dimensions at 120 K: a = 7.2652(9), b = 7.4458(2), c = 9.3030(3) Å, α = 79.504(1)°, β = 84.755(1)°, γ = 71.676(2)°; R₁ = 0.0349.     

Kristallstruktur,Infrarot‐ und Ramanspektren von Kupfertrihydrogenperiodatmonohydrat,CuH3IO6 · H2O

Crystal Structure, Infrared and Raman Spectra of Copper Trihydrogenperiodate Monohydrate, CuH₃IO₆ · H₂O The hitherto unknown compound CuH₃IO₆ · H₂O was studied by X‐ray, IR‐ and Raman spectroscopic methods. The crystal structure was determined by X‐ray single‐crystal studies (space group P2₁2₁2₁, Z = 4, a = 532.60(10), b = 624.00(10), c = 1570.8(3) pm, R1 = 1.85%, 1559 unique reflections (I > 2σ(I))). Isolated, meridionally configurated H₃IO₆^2– ions are coordinated to the copper ions forming double‐ropes in [100]. These ropes are connected in [010] and [001] by hydrogen bonds. The copper ions possess a square pyramidal co‐ordination with the hydrate H₂O on top. The infrared and Raman spectra as well as group theoretical treatment are presented and discussed with respect to the strength of the hydrogen bonds and the co‐ordination of the CuO₅₍₊₁₎ polyhedra and the H₃IO₆^2– ions at the C₁ lattice sites. The hydrogen bonds of the H₂O molecules and H₃IO₆^2– ions (HO–H…O–IO₅H₃ and H₂IO₅O–H…O–IO₅H₃) greatly differ in strength, as shown from both the respective O…O distances: 282.6 and 298.6 pm (H₂O), and 258.8, 259.7, and 270.9 pm (H₃IO₆^2–) and the OD stretching modes of isotopically dilute samples: 2498 and 2564 cm^–1 (90 K) (HDO), and 1786, 2024, and 2188 cm^–1 (H₂DIO₆^2–). The IO stretching modes of the H₃IO₆^2– ions (696–788 cm^–1 and 555–658 cm^–1, 295 K) display the different strength of the respective I–O and I–O(H) bonds (r_I–O: 181.1–188.3 pm and 189.2–194.5 pm).     

Kristallstruktur und schwingungsspektrometrische Daten von cis-Na2[Pd(SO3)2en] · 4 H2O

Crystal Structure and Data from Vibrational Spectra of cis-Na₂[Pd(SO₃)₂en] · 4 H₂O The compound cis-Na₂[Pd(SO₃)₂en] · 4 H₂O (en = 1,2-diaminoethane) crystallizes in the orthorhombic space group Pnma with a = 623.7(2), = 1070.9(10), c = 1989.5(30) pm and Z = 4. In the [Pd(SO₃)₂en]^2? anions the trans-influence of the sulfite ligands manifests itself in long Pd? N bonds with short Pd? S distances. A set of Na⁺ ions is present in face-sharing octahedra Na(OH₂)₆⁺, forming rods [Na(OH₂)_6/2]⁺ parallel to [100]. A second set of Na⁺ ions is surrounded by two H₂O molecules and four O atoms from SO₃ ligands of two anions to form likewise octahedra with face-sharing, yielding rods [Na(OH₂)_2/2{(OSO₂)₂Pd en}_2/2]^? parallel to [100]. Comparatively low v(Pd? N)-frequencies reveal the trans-influence of the sulfite ligands also in the vibrational spectra.     

Gitterschwingungsspektren. LXIII. Be(lO3)2 · 4 H2O,ein Hydrat mit ungewöhnlicher Bindungsstruktur und Gitterdynamik

Lattice Vibration Spectra. LXIII. Be(IO₃)₂ · 4 H₂O, a Hydrate with Unusual Bonding and Lattice Dynamics The IR and Raman spectra (4000–50 cm^?1) of Be(IO₃)₂ · 4 H₂O and of deuterated specimens are recorded at 90 and 300 K and discussed in terms of the unusual relations of the masses of the atoms involved and the large polarization power of the beryllium ions. Thus, the translatory modes of the Be²⁺ ions (BeO₄ skeleton vibrations), the librations of the H₂O molecules, and the internal vibrations of the IO₃^? ions in the spectral regions of 300–400 and 600–1000 cm^?1 couple and coincide producing unusual v_H/v_D isotopic ratios of partly < 1. The H-bond donor strengths of the water molecules is so much increased (due to the very large ionic potential of Be²⁺ ions, viz. 49 e nm^?1) (synergetic effect) that the H-bonds formed are similar in strength as those in hydrates of hydroxides with the very strong H-bond acceptor group OH^? (v_OD of matrix isolated HDO molecules 2 074 and 2 244 (H₂O I) and 2 206 and 2 349 cm^?1 (H₂O II))     

Erdalkali-Fluoromanganate(III): BaMnF5 · H2O und SrMnF5 · H2O

Alkaline Earth Fluoromanganates(III): BaMnF₅ · H₂O and SrMnF₅ · H₂O Solid BaF₂ or SrF₂ forms with solutions of Mn³⁺ in aqueous hydrofluoric acid precipitates of hitherto unknown BaMnF₅ · H₂ and SrMnF₅ · H₂O respectively. X-ray structure determination on single crystals of both isotypic compounds (space group P2₁/m, Z = 2; BaMnF₅ · H₂O: a = 537.0(3), b = 817.2(2), c = 628.0(4) pm β = 111.17(5)°, R_w = 0.035 for 1403 reflections; SrMnF₅ · H₂O: a = 510.8(1), b = 792.0(2), c = 610.6(1) pm, β = 110.24(1)° R_w = 0.068 for 539 reflections) reveal pure [MnF₆]^3? octahedra connected with each other to infinite chains by sharing trans corners. The H₂O molecules are coordinated to the alkaline earth ions only and form weak O? H…F hydrogen bonds. The pronounced weakening of the Mn? F bonds within the chain direction (Mn? F 2X 212.7(1)/210.8(5) pm, 2X 183.8(3)/181.8(9) pm, 2X 186.9(2)/187.2(8) pm) may be due by halves to the Jahn-Teller-effect as can be deduced by bond valence calculations.     

Mehrkernige Kobaltkomplexe. II. Herstellung und Struktur von [(tren) (NH3)Co(O2)Co(NH3) (tren)](SCN)4 · 2H2O

Polynuclear Cobalt Complexes. II. Preparation and Structure of [(tren) (NH₃)Co(O₂)Co(NH₃) (tren)](SCN)₄ · 2H₂O The title compound is obtained on oxygenation of [Co(tren)(H₂O)₂]²⁺ in 6M aqueous ammonia or by ligand exchange starting from [(NH₃)₅Co(O₂)Co(NH₃)₅]-(NO₃)₄. An X-ray structure determination was made. The substance forms monoclinic crystals, space group P2₁/c, lattice constants a=10,135, b=8,473, c=19,484 Å, β=108,58°, with two formula units in the cell. The final R is 0,066. The binuclear cation has a center of symmetry, so the Co? O? O? Co unit is planar; the Co? O? O angle is 111,5°. The tertiary nitrogen atoms of both chelate groups are cis to the O₂ bridge, as found in doubly bridged [(tren)Co(O₂,OH)Co(tren)](ClO₄)₃ · 3H₂O. On acidification in solution, the singly bridged cation [(tren) (NH₃)CoO₂Co(NH₃)(tren)]⁴⁺ (a) loses the bound O₂ completely. But unlike the doubly bridged cation b , the rate of dissociation of a is independent of pH (Fig. 5). At higher pH (8–10) bridging a→b (Fig. 2) occurs. Both reactions must have the same rate determining step, the first order rate constants being of the order of 2 · 10^?3 s^?1 (25°, 0,35M KCl).     

Zur Kenntnis der Hydrate des Typs MX2 · 1 H2O mit M = Sr,Ba und X = Cl,Br, I. Kristallstrukturen des Strontiumchlorid-Monohydrats,SrCl2 · 1 H2O,und des Strontiumbromid-Monohydrats,SrBr2 · 1 H2O

On Hydrates of the Type MX₂ · 1 H₂O with M = Sr, Ba and X = Cl, Br, I. Crystal Structures of Strontium Chloride Monohydrate, SrCl₂ · 1 H₂O, and Strontium Bromide Monohydrate, SrBr₂ · 1 H₂O The structures of SrCl₂ · 1 H₂O, orthorhombic, Pnma, a = 1088.1(1), b = 416.2(1), c = 886.4(1) pm, Z = 4, d_c = 2.92 Mg m^?3, R = 0.052 for 755 reflections, and of SrBr₂ · 1 H₂O, orthorhombic, Pnma, a = 1146.4(1), b = 429,5(1), c = 922.9(1) pm, Z = 4, d_c = 3.88 Mg m^?3, R = 0.056 for 762 reflections have been determined from a Patterson synthesis and refined by Fourier and Least Squares methods. The structure consists of [SrX₂ = H₂O]_n-layers normal to [100] and Sr? H₂O? Sr? H₂O-chains parallel [010]. The Sr? O distances are 265.1(3) pm, SrCl₂ · 1 H₂O, and 265.9(4) pm, SrBr₂ · 1 H₂O. The shortest Sr? Cl and Sr? Br distances (298.9(1) and 315.3(1) pm) are within the layers. The environment of oxygen and strontium is a distorted tricapped trigonal prism. The orientation of the water molecules has been determined from vibrational spectroscopic measurements. The hydrogen atoms H₁ and H₂ form bifurcated hydrogen bonds of different strength to neighbouring halide ions. The corresponding O···X distances are 331.9(4) and 320.2(4) pm, SrCl₂ · 1 H₂O, and 340.8(4) and 333.8(4) pm, SrBr₂ · 1 H₂O. The other O? X distances are between 310.3(5) and 323.7(5) pm, SrCl₂ · 1 H₂O, and 323.5(5) and 333.2(6) pm, SrBr₂ · 1 H₂O.