Röntgenographische Kristallstrukturuntersuchung von Magnesiumperrhenat‐tetrahydrat Mg(ReO₄)₂ · 4 H₂O

Abstract

Es wurde die Kristallstruktur von Magnesiumperrhenat‐tetrahydrat, Mg(ReO4)2 · 4 H2O, das sich bei 25°C aus wäßriger Lösung einkristallin ausscheidet, röntgenographisch bestimmt. Die Verbindung kristallisiert triklin, in der Raumgruppe P1 mit den Gitterkonstanten a = 769,2 pm, b = 702,6 pm, c = 646,9 pm, α = 108,279°, β = 92,388°, γ = 120,418°, Z = 1, ϱber. = 3,58 g = cm−3, ϱexp. = 3,62 g · cm−3. Die Struktur wurde in anisotroper Näherung mit 2990 unabhängigen Reflexen bis zu einem R‐Wert von 7,4% verfeinert. Die Re‐Atome sind tetraedrisch, die Mg‐Atome oktaedrisch koordiniert.

CRYSTAL STRUCTURE OF A NEW BISMUTH PERRHENATE Bi(Re0(4))3H(2)0

“…; tetrahedra is approximately the same observed for rare-earth perrhenates, transition metal perrhenates and earth alkaline perhenates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The dependence of coordination number upon the Pauling`s ionic radii 21 observed for the central cation in this case, agrees with the relationship for other related compounds. Namely, when the ionic radius of the metal lays in the range 0.6Å to 0.8Å the coordination number is 6 and when the ionic radii lays in the range 1.00Å to 1.20Å the coordination number is 9.…”

“…In these perrhenates, the coordination number of the central cation depends mainly on the size of the 3+ ion. This dependence is also observed for many others compounds based on perrhenate as a ligand, including alkalines-earth metals, transition metals and rare-earth ions as central cation [6][7][8][9][10][11][12][13][14][15][16][17][18] . All of them with oxidation states 2+ or 3+.…”

Pertechnetates – A Structural Study Across the Periodic Table

“…[Mg(TcO 4 ) 2 (H 2 O) 4 ] ( 2‐MgTc ) (Figure 2) is a centrosymmetric compound that crystallises in the triclinic space group P ‐1 and is isostructural to [Mg(ReO 4 ) 2 (H 2 O) 4 ] [33] and [M(TcO 4 ) 2 (H 2 O) 4 ] (M=Co ( 10‐CoTc ), Ni ( 11‐NiTc ), Cu ( 12‐CuTc ), Zn ( 13‐ZnTc )) described further below. The Mg 2+ centre forms a distorted octahedron with four oxygen atoms (O5−O6) of the water molecules and two oxygen atoms (O1) of the [TcO 4 ] − ligands.…”

“…The crystals are highly hygroscopic and dissipate within seconds when outside of a desiccator at room temperature due to absorption of ambient moisture from the air. 2) is a centrosymmetric compound that crystallises in the triclinic space group P-1 and is isostructural to [Mg(ReO 4 ) 2 (H 2 O) 4 ] [33] [Ca(TcO 4 ) 2 (H 2 O) 4 ] (3 a-CaTc) (Figure 3) crystallises in the orthorhombic space group Pccn. The Ca 2 + centre forms a distorted square antiprism, with four oxygen atoms (O5À O6) of the water molecules, and four oxygen atoms (O1 and O3) of the pertechnetate units.…”