Showing papers in "Zeitschrift Fur Kristallographie-new Crystal Structures in 1995"
TL;DR: In this paper, a series of silver complexes with the unsatu-rated isomeric dicarboxylic acids, maleic and fumaric, has been prepared and the structures of three of them were determined by X-ray diffraction.
Abstract: A series of silver (I) complexes with the unsatu- rated isomeric dicarboxylic acids, maleic and fumaric, has been prepared and the structures of three of these, silver(I) hydrogen maleate, (1), silver(I) maleate, (2) and silver(I) fumarate, (3), were determined by X-ray diffraction. All three structures are polymeric, with (1) and (2) based on bis(carboxylato-0, 0‘) dimers. With (1), a strong intramolecular hydrogen bond is found [O. O, 2.494(2) A], involving the acidic proton and the cis-related carboxylate group. In this respect it is similar to maleic acid and other hydrogen maleates. With (2), a unique feature is the presence of an ethylene-Ag π-bond to one of the independent silver ions [Ag —C, 2.448(5) A] giving angle distortion about the dimer unit. The polymeric structure of (3) is based on an unusual cyclic, open figure-eight Ag4 complex unit involving four different carboxy-lato-(0, 0‘) interactions. This results in three separate Ag. Ag contacts [2.924(1) A, 2.925(1) A, 3.090(1) A].
17 citations
TL;DR: In this paper, the average structure was refined to R = 0.049 from 2695 reflections, and a model was proposed for the real structure taking into account about 200 superstructure reflections.
Abstract: Slawsonite (SrAl 2 Si 2 O 8 ) from Sarusaka, Kochi Prefecture, Japan, is triclinic, space group P1, with a = 0.6145(1) nm, b = 0.8987(2) nm, c = 0.7456(3) nm, α = 90.01(3)°, β = 90.34(3)° and γ = 89.98(3)°, Z = 4 at T = 298 K. The cell dimensions are similar to the previous assignment to the monoclinic space group P2 1 /a. The average structure was refined to R = 0.049 from 2695 reflections. A model is proposed for the real structure taking into account about 200 superstructure reflections. Thermal analysis revealed a phase transition to P2 1 /a at 593 K which is considered a new type of transition for the paracelsian-slawsonite group.
10 citations