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  • Author: Edward R. T. Tiekink x
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Abstract

The structure determination of 5-carboxy-2-thiouracil shows it to exist in the lactam-thione form. Extensive hydrogen bonding involving all possible donors and acceptors leads to the formation of interconnected 8- (x2), 10-, 16- and 20-membered rings and a two-dimensional layer structure; no evidence for base stacking was found.

Abstract

The crystal structure of the title compound, (C6H5)3PAuS2- COCH3, has been determined at room temperature. Crystals are triclinic, P[unk], a = 10.887(2), b = 11.074(2), c = 8.862(1) Å, α = 104.08(1), β = 95.97(1), γ = 99.88(2)°, Z = 2, Dm = 1.85; Dx = 1.865 Mg m−3. The structure was refined by a full-matrix least-squares procedure to final R 0.025 for 3112 unique reflections measured on a CAD-4 diffractometer. The gold atom is linearly coordinated by the P atom and a S atom of the monodentate xanthate ligand. The angle subtended at the gold atom is 174.1(1)° and the associated Au – P and Au – S distances are 2.261(1) and 2.310(1) Å respectively. The deviation from ideal linear geometry has been rationalized in terms of a weak intermolecular Au… O interaction.

Abstract

The crystal structure of the title compound has been examined at room temperature. Crystals are triclinic, space group P[unk] with a = 4.2859(7), b = 6.036(1), c = 10.6563(5) Å, α = 73.35(1), β = 83.81(1), γ = 89.11(2)°, V = 262.5(2) Å3, Z = 2, Dx = 1.621 g cm−3. The structure was refined by a full-matrix least-squares procedure to final R = 0.063 for 1003 reflections with I ⩾ 3.0 σ(I) measured on a CAD4 diffractometer. The molecule is essentially planar and exists in the lactam-thione form with the C(2) – S(2) and C(4) – O(4) distances being 1.683(3) and 1.227(4) Å respectively. Intermolecular hydrogen bonding, involving the sulphur and oxygen atoms, leads to infinite ribbons which stack in a layer structure; the vertical distance between successive layers is approximately 3.48 Å.

Abstract

The title compound, 2-thiophenecarboxylic acid, crystallizes in the monoclinic space group P21/c with unit cell parameters a = 5.698(1) Å, b = 5.043(1) Å, c = 19.712(2) Å, β = 98.49(1)°, Z = 4; Dx = 1.519 Mg m−3. The structure was solved by direct-methods and refined by a full-matrix least-squares procedure on 958 reflections to final R = 0.034. The S(1) – C(2) and S(1) – C(5) bond distances are 1.707(2) Å and 1.695(2) Å respectively. In the crystal lattice the molecules associate via the carboxylic acid groups to form centrosymmetric dimers.