(Mg1–xCrx)2P2O7, CaCrP2O7, SrCrP2O7 und BaCrP2O7 – Neue Diphosphate des zweiwertigen Chroms

Contributions on Crystal Chemistry and Thermal Behaviour of Anhydrous Phosphates. XXXI. (Mg_1–xCr_x)₂P₂O₇, CaCrP₂O₇, SrCrP₂O₇ and BaCrP₂O₇ – New Diphosphates of Divalent Chromium In the quasi‐binary systems A₂P₂O₇/Cr₂P₂O₇ (A = Mg, Ca, Sr, Ba) the solid solution (Mg_1–xCr_x)₂P₂O₇ as well as the new compounds CaCrP₂O₇, SrCrP₂O₇, and BaCrP₂O₇ have been synthesized and characterized for the first time. In the whole experimental range (0.01 < x < 0.94; T = 950 °C) the solid solution (Mg_1–xCr_x)₂P₂O₇ is isotypic to the pure phases β‐Mg₂P₂O₇ and β‐Cr₂P₂O₇; but no phase transition (β → α) to a low‐temperature modification, as in Mg₂P₂O₇ and Cr₂P₂O₇, was found. CaCrP₂O₇ ( A ), SrCrP₂O₇ ( B ), and BaCrP₂O₇ ( C ), phases without detectable homogenity range in the other quasi‐binary systems are not structurally related to each other, but are isotypic to the corresponding compounds containing cobalt. [( A ): P‐1, Z = 2, a = 6.312(2) Å, b = 6.499(2) Å, c = 6.916(2) Å, α = 83.12(3)°, β = 88.37(3)°, γ = 67.72(3)°, 3235 independent reflections, R1 = 0.041, wR2 = 0.112; ( C ): P‐1, Z = 2, a = 5.382(8) Å, b = 7.271(8) Å, c = 7.589(4) Å, α = 103.33(7)°, β = 89.91(9)°, γ = 93.6(1)°, 1571 independent reflections, R1 = 0.085, wR2 = 0.31]. We have reported earlier details on SrCrP₂O₇. The coordination of Cr²⁺ by oxygen is distorted octahedral in ( A) , while in the structures of ( B) and ( C) square‐pyramidal environment is found. The results of UV/VIS‐spectroscopic and magnetic measurements as well as IR‐spectra of the diphosphates are reported.     

KZn(HP2O7)·2H2O and KMn(HP2O7)·2H2O: acid pyrophosphate metallates(II) with layer structures

The crystal structures of the isomorphous title compounds, namely potassium zinc hydrogen pyrophosphate dihydrate and potassium manganese hydrogen pyrophosphate dihydrate, consist of acidic pyrophosphate–metallate(II) layers joined by K⁺ ions and hydrogen‐bridging bonds. The Zn²⁺/Mn²⁺ ions are octahedrally surrounded by four pyrophosphate O atoms and by two water mol­ecules. The (HP₂O₇)^3? anions exhibit eclipsed conformations. The metal ions and water O atoms lie on mirror planes, as does the central O atom of the (HP₂O₇)^3? anion.     

Strontium hexabromodicadmate(II) octahydrate

The ternary system SrBr₂–CdBr₂–H₂O was investigated at room temperature. The title phase, SrCd₂Br₆·8H₂O, has been isolated from this system and its structure determined by single‐crystal X‐ray diffraction. The structure consists of infinite double chains of CdBr₆ octahedra and chains of Sr(H₂O)₉ polyhedra packed along the b axis. The interaction between these two isolated chains occurs through O—H⃛O and O—H⃛Br hydrogen bonds. The structure is compared with that of SrCd₂Cl₆·8H₂O.     

Kristallstrukturen des Sr(BrO3)2 · H2O,Ba(BrO3)2 · H2O,Ba(IO3)2 · H2O,Pb(CIO3)2 · H2O und Pb(BrO3)2 · H2O

Crystal Structure of Sr(BrO₃)₂ · H₂O, Ba(BrO₃)₂ · H₂O, Ba(IO₃)₂ · H₂O, Pb(ClO₃)₂ · H₂O, and Pb(BrO₃)₂ · H₂O The crystall structures of the isostructural halates Sr(BrO₃)₂ · H₂O, Ba(BrO₃)₂ · H₂O, Ba(IO₃)₂ · H₂O, Pb(ClO₃)₂ · H₂O, and Pb(BrO₃)₂ · H₂O were determined using X-ray single crystal data (monoclinic space group C2/c? C, Z = 4), The mean bond lengths and bond angles of the halate ions in the Ba(ClO₃)₂ · 1 H₂O-type compounds, which correspond to those of other halates, are Cl? O, 149.0, Br? O, 165.9, I? O, 180.2 pm, ClO₃^?, 106.4, BrO₃^?, 104.0, and IO₃^?, 99.6°. The structure data obtained are discussed in terms of possible orientational disorder of the water molecules, strengths of the hydrogen bonds, influence of the lead ions on the structure, and site group distortion of the halate ions.     

NaMn6(P2O7)2(P3O10) and KCd6(P2O7)2(P3O10)

The crystal structures of two new diphosphates, sodium hexamanganese bis­(diphosphate) triphosphate, NaMn₆(P₂O₇)₂(P₃O₁₀), and potassium hexacadmium bis­(diphosphate) triphosphate, KCd₆(P₂O₇)₂(P₃O₁₀), confirm the rigidity of the M₆(P₂O₇)₂(P₃O₁₀) matrix (M is Mn or Cd) and the relatively fixed dimensions of the tunnels extending in the a direction of the unit cell. The compounds are isomorphous; the P₂O₇^4? anion and the alkali metal cations lie on mirror planes. Bond‐valence analysis of the bonding details of the atoms found within the tunnels permits a prediction of the conductivity.