Richard Pažout

Crystal structure of natural orthorhombic Ag0.71Pb1.52Bi1.32Sb1.45S6, a lillianite homologue with N = 4; comparison with gustavite

The crystal structure of natural orthorhombic Ag0.71Pb1.52Bi1.32Sb1.45S6, a lillianite homologue with N = 4, from hydrothermal veins at Kutna Hora in central Bohemia, Czech Republic, has been refined from single-crystal X-ray data to final R w = 5.08 %. The symmetry is orthorhombic, space group Cmcm , with a = 4.2539(8), b = 13.3094(8), c = 19.625(1) A, V = 1111.1(2) A3, Z = 4. On the basis of electron-microprobe analysis, the formula is Ag0.69Pb1.56(Bi1.32Sb1.37)∑=2.69(S6.04Se0.01)∑6.05 with N chem = 3.94, Bi/(Bi + Sb) = 0.49 and a gustavite substitution percentage L% = 70.5, which characterize the phase as a natural orthorhombic Sb–Bi 4,4L member of the lillianite homologous series. The structure contains seven independent positions: three metal sites M 1, M 2 and M 3 and four sulphur positions. The crystal structure consists of blocks of diagonal chains of four octahedra M 1 (Bi/Ag/Sb) – M 2 (Sb/Pb/Bi) – M 2 – M 1 separated by Pb atoms in bicapped trigonal prismatic coordination of the site M 3. The marginal octahedron of the chain of four octahedra is formed by one mixed site M 1 containing 52 % Bi, 35.6 % Ag and 12.4 % Sb while the central M 2 octahedron is a mixed site containing 60.1 % Sb, 25.9 % Pb and 14 % Bi. The mixed population of the M 1 site results in orthorhombic symmetry, space group Cmcm , with a 4 A a -repeat while in natural gustavite, the alternating occupation of the M 1 site by Ag and Bi atoms (which are thus two sites M 1a and M 1b) reduces the symmetry to monoclinic, space group P 21/ c , with an 8 Arepeat. The structure is similar to that of Ag-free lillianite.

A bromine analogue of picoplatin: a new substance from the group of platinum-based chemotherapeutics.

A new substance, cis-amminedibromido(2-methylpyridine-κN)platinum(II), cis-[PtBr2(C6H7N)(NH3)], which is a potential platinum-based antineoplastic agent for the treatment of patients with solid tumors, has been synthesized and structurally characterized. There is one molecule in the asymmetric unit and molecules are linked via two symmetry-independent N-H···Br hydrogen bonds into zigzag chains running parallel to the c axis. C-H···Br hydrogen bonds crosslink these chains to give a layer parallel to (010). N-H···Br hydrogen bonds and π-π stacking interactions between pairs of pyridine rings stack the layers along b.

Natural monoclinic AgPb(Bi2Sb)3S6, an Sb‐rich gustavite

The crystal structure of the Sb-rich variety of the mineral gustavite, silver lead tris(dibismuth/antimony) hexasulfide, AgPb(Bi(2)Sb)(3)S(6), consists of blocks of diagonal chains of four octahedra, viz. M1a (Bi), M2a (Sb/Bi), M2b (Bi/Sb) and M1b (Ag), separated by Pb atoms in a trigonal prismatic coordination. Two marginal octahedral sites, M1a and M1b, where the gustavite substitution Ag(+) + Bi(3+) = 2Pb(2+) takes place, are formed by Bi and Ag, respectively. Two central octahedra, M2a and M2b, where the Bi(3+) = Sb(3+) substitution takes place, are formed by two mixed Bi/Sb sites with different occupancies of Bi and Sb. The alternating occupation of the M1 site by Bi and Ag atoms (which thus creates two distinct sites M1a and M1b) results in the monoclinic space group P2(1)/c. A statistical distribution of Ag/Bi in the M1 position (one mixed Ag/Bi site) was reported for synthetic gustavite, resulting in the orthorhombic space group Cmcm.

Alaptide from synchrotron powder diffraction data.

The title compound [systematic name: (8S)-8-methyl-6,9-diazaspiro[4.5]decane-7,10-dione], C9H14N2O2, consists of two connected rings, viz. a piperazine-2,5-dione (DKP) ring and a five-membered ring. The DKP ring adopts a slight boat conformation and the bonded methyl group is in an equatorial position. The five-membered ring is in an envelope conformation. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link molecules into chains running parallel to the c axis.

Synthesis and characterization of two new chiral Kemp’s acid derivatives: structures fixed by a peculiar system of N–H···O, C–H···O and C–H···N hydrogen bonds

Abstract New chiral imide-oxazoline derivatives of Kemp’s acid were synthesized with the aim to produce new ligands suitable for catalytic asymmetric reactions. Compound 1 is C18H28N2O3, systematic name (1R, 5S, 7R)-7-[(S)-4-tert-butyl-4,5-dihydrooxazole-2-yl]-1,5,7-trimethyl-3-azabicyclo-[3.3.1]-nonane-2,4-dione. Compound 2 is C21H26N2O3, systematic name (1R,5S,7R)-7-[(S)-4-benzyl-4,5-dihydrooxazole-2-yl]-1,5,7-trimethyl-3-azabicyclo-[3.3.1]-nonane-2,4-dione. Both compounds contain two molecules with very similar conformations in the asymmetric unit. The two structures were characterized by single crystal X-ray diffraction. DFT calculations of two possible distinct conformations were performed to elucidate the differences between the preferred conformation in vacuo and the one observed in the single crystal. Also, charges on the key atoms of the compounds were compared with a common ligand used for asymmetric transfer hydrogenation.

A new polymorph of succinylcholinium diiodide: comparison of succinylcholinium structures

The title compound {systematic name: trimethyl[2-({4-oxo-4-[2-(trimethylazaniumyl)ethoxy]butanoyl}oxy)ethyl]azanium diiodide}, C(14)H(30)N(2)O(4)(2+)·2I(-), is a salt of the succinylcholinium cation. There is one formula unit in the asymmetric unit, represented by two anions and two halves of two cations which lie on centres of inversion. The component species are stabilized by electrostatic interactions, and C-H···I and C-H···O hydrogen bonds are also present.