Space Group Unit Research Articles

The Synthesis and Crystal Structure of U7O2Se12

AbstractThe new compound U7O2Se12 was synthesized at 1173 K as a result of both unintentional and intentional oxygen contamination. The composition balances with formal charges of +4, –2, and –2 for U, O, and Se, respectively. U7O2Se12 crystallizes with one formula unit in space group C$\rm^{1}_{3h}$‐P$\bar{6}$ of the hexagonal system in a cell of dimensions a = 11.3222(4) Å, c = 4.1362(1) Å. The structure of U7O2Se12 closely resembles that of the An7Te12 (An = Th, U) compounds, but contains cavities, in which oxygen atoms are coordinated to three uranium atoms in a trigonal planar arrangement. It is not known if other members of the An7Q12 family (An = Th, U; Q = S, Se, Te) are actually An7O2Q12 compounds.

6-Amino-5,5-diisopropyl-5H-pyrimidine-2,4-dione hemihydrate

In the title compound, C10H17N3O2·0.5H2O, two 6-amino-5,5-diiso­propyl-5H-pyrimidine-2,4-dione mol­ecules and one mol­ecule of water constitute the asymmetric unit in space group P\overline 1. One mol­ecule forms a one-dimensional hydrogen-bonded chain; the chains are cross-linked by hydrogen bonds to the second mol­ecule and the water mol­ecule.

New minerals approved in 2000 by the Commission on New Minerals and Mineral Names (CNMMN) International Mineralogical Association

NO OTHER INFORMATION WILL BE RELEASED BY THE COMMISSION The information given here is provided by the Commission on New Minerals and Mineral Names, I.M.A., for comparative purposes and as a service to mineralogists working on new species. Each mineral is described in the following format: IMA No. Chemical Formula (any relationship to other minerals) Crystal system, space group unit cell parameters Colour; lustre; diaphaneity. Optical properties. Strongest lines in the X-ray powder diffraction pattern. The names of these approved species are considered confidential information until the authors have published their descriptions or released information themselves. IMA No. 2000-001 IMA No. 2000-002 IMA No. 2000-003 IMA No. 2000-004 IMA No. 2000-005

Structural investigation of homonuclear Pt2 and heteronuclear PdPt complexes containing a metal–metal bond bridged by hydrido and sulfido ligands

The complex [Pt2(μ-H)(μ-S)(dppe)2](PF6) undergoes a displacive order–disorder transformation at ca 230 K. The low-temperature structure is ordered with one cation–anion pair as the asymmetric unit in space group P21/n. At room temperature the b axis is halved and the space group is P2/n, imposing crystallographic twofold rotation symmetry on both ions; the anion shows major disorder and there is probably minor disorder in the cation, but its internal geometry remains essentially unchanged. The heteronuclear complex [PdPt(μ-H)(μ-S)(dppe)2](PF6) is isostructural with the Pt2 complex at room temperature. All three structures have been determined crystallographically and both complexes have been extensively characterized by NMR spectroscopy, unambiguously confirming the genuine heteronuclear nature of the mixed-metal complex and the presence of the bridging hydride ligand.

Structures of a semiconducting and a metallic phase in the Fe yZrSe 2 system

Studies of the Fe y ZrSe 2 system have led to a semiconducting phase for y =0.16 and to a metallic phase for y =0.41. The structures of both phases have been established through single-crystal X-ray measurements. The compound Fe 0.16 ZrSe 1.94 crystallizes with one formula unit in space group D 3 3 d − P ¯3 m l of the trigonal system in a cell of dimensions a =3.763 (1), c =6.118(1) . The structure is of the CdI 2 -NiAs intermediate type with octahedral coordination of Se atoms about both the Fe and Zr atoms. The compound Fe 0.41 ZrSe 2 , the metallic phase, crystallizes with six formula units in space group D 6 6 -P6 3 22 of the hexagonal system in a cell of dimensions a =6.011(1), c =12.787(1) . The structure is the same as that of M Nb 3 S 6 ( M =Mn, Fe, Co, Ni). In this structure, the Fe atoms are in octahedral holes while the Zr atoms are trigonal prismatically coordinated by Se atoms.