On the systematics and description of polyions of linked polyhedra

Na2Cu+[Cu2+ 3O](AsO4)2Cl and Cu3[Cu3O]2(PO4)4Cl2: two new structure types based upon chains of oxocentered tetrahedra

Single crystals of Na2Cu+[Cu2+ 3O](AsO4)2Cl (1) and Cu3[Cu3O]2(PO4)4Cl2 (2) were prepared by chemical vapor transport reactions. Both crystal structures are based upon the same [O2Cu6]8+ chains formed by corner-sharing (OCu4)6+ tetrahedra and interconnected by (TO4)3− (T = P, As) tetrahedra into porous {[OCu3](TO4)2Cl}3− frameworks. The channels within the frameworks are occupied by Na+, Cu+ and Cl− ions in the crystal structure of 1, whereas the channels in the structure of 2 contain edge-sharing CuO4Cl tetragonal pyramids. Both compounds are structurally related to the previously described synthetic Na2Cu+[Cu2+ 3O](PO4)2Cl and NaCu2+[Cu2+ 3O](PO4)2Cl. The compound 2 is structurally and chemically related to yaroshevskite, Cu3[Cu3O]2(VO4)4Cl2, a mineral discovered in volcanic fumaroles, but the two structure types are drastically different. The crystal chemical analysis of the title and related compounds allows to recognize a family of at least four compounds based upon {[OCu3](TO4)2Cl}3− frameworks with channels occupied by different chemical constituents.

Crystal chemistry of inorganic compounds based on chains of oxocentered tetrahedra III. Crystal structure of georgbokiite, Cu5O2(SeO3)2Cl2 1

The monoclinic crystal structure of georgbokiite, a new mineral with the chemical composition Cu5O2(SeO3)2Cl2 (a = 6.030(1) Å), b = 13.744(3) Å, c = 5.562(1) Å, β = 95.75(1)°, V = 458.6(2) Å3, Z = 2, P21/c) has been refined to an R index of 0.043 [wR = 0.108). The structure is similar to that previously determined for synthetic Cu5Se2O8Cl2. It is based on the unbranched zweier chains {uB, 1χ 1} [O2Cu5] running parallel to the c axis which are composed of [OCu4] oxocentered copper tetrahedra linked through corners and edges in turn. The pyramidal (SeO3) groups are in “face-to-face” positions relative to the [OCu4] tetrahedra and together with the oxocentered chains form the more complex chains {[O2Cu5](SeO3)2} lying side by side in the (010) plane. The chloride anions are located between the chains to link them into a three-dimensional framework. The main structural features of other inorganic compounds based on single chains of oxocentered condensed copper tetrahedra are discussed in comparison.

Crystal structure of Pb10O7(OH)2F2(SO4) and crystal chemistry of lead oxysulfate minerals and inorganic compounds

The crystal structure of Pb10O7(OH)2F2(SO4) (triclinic, P1̅, a = 9.6637(16), b = 10.1922(17), c = 11.1407(18) Å, α = 110.978(3), β = 91.795(3), γ = 107.020(3)°, V = 968.2(3) Å3) has been solved by direct methods and refined to R1 = 0.050 (wR = 0.089). There are ten symmetrically unique Pb2+ cations in the structure all of which have highly asymmetric coordination polyhedra owing to presence of stereoactive 6s 2 lone pairs of electrons. The structure is based upon [O7Pb10] zigzag chains of edge-sharing OPb4 oxocentered tetrahedra. The observed [O7Pb10] chain is the most complex chain of oxocentered tetrahedra known so far and was not observed previously in structures of inorganic compounds. The chains run along [011] and their plane is parallel to (111). The chains form sheets parallel to (111). The SO4) tetrahedra, F– anions and OH groups are between the sheets providing their linkage into three-dimensional structure. A comparison of the structure with other Pb oxysulfates is given in the framework of theory of complexes of anion-centered tetrahedra.

Minerals and synthetic Pb(II) compounds with oxocentered tetrahedra: review and classification

The crystal structures of minerals and inorganic compounds with OPb4 oxocentered tetrahedra are reviewed. It is shown that the OPb4 tetrahedral units may link by sharing common Pb atoms to form structural units of various shape and dimensionality. These units determine basic topology of the structures and influence their stability and properties. The high strength of the OPb4 te trahedral units involves interplay between high basicity of additional O2– anions and stereochemical activity of the 6s 2 lone electron pairs on Pb2+ cations. The structural chemistry of polycations based upon OPb4 tetrahedra, in general, follows major trends previously observed for cation-centered tetrahedral units (silicates, phosphates, metal sulphides with MS4 tetrahedra, etc.). One may conclude that the basic structural correlations depend upon size and charge parameters of the ions only, irrespective of their positive or negative sign.