The crystal structure of bideauxite, Pb2(2+) Ag+ Cl3 F (OH), cubic, a 14.1273(6) Å, V 2819.2(4) Å3, Fdbar3m, Z = 16, D-calc = 6.26 g.cm-3, has been solved by direct methods and refined to an R index of 2.8% for 324 observed (5 sigma) reflections measured with MoK-alpha X-radiation. There is one unique Ag site surrounded by an octahedral array of CP anions, and one Pb site surrounded by nine anions with a very asymmetrical distribution of bonds and bond-lengths characteristic of stereoactive lone-pair behavior of Pb2+. Four (AgCl6) octahedra link by sharing corners to form an [Ag4Cl18] cluster, and these clusters link by sharing corners to form a three-dimensional chequerboard arrangement, with [Pb4 (OH)(2) F2 Cl18] clusters filling the interstices. The structure of bideauxite is not related to those of the paragenetically related minerals boleite and pseudoboleite.
Stereoactive lone-pair behaviour of Pb2+ in the crystal structure of bideauxite: Pb2+2Ag+Cl3F(OH)
MERLINO, STEFANO;PASERO, MARCO;PERCHIAZZI, NATALE
1999-01-01
Abstract
The crystal structure of bideauxite, Pb2(2+) Ag+ Cl3 F (OH), cubic, a 14.1273(6) Å, V 2819.2(4) Å3, Fdbar3m, Z = 16, D-calc = 6.26 g.cm-3, has been solved by direct methods and refined to an R index of 2.8% for 324 observed (5 sigma) reflections measured with MoK-alpha X-radiation. There is one unique Ag site surrounded by an octahedral array of CP anions, and one Pb site surrounded by nine anions with a very asymmetrical distribution of bonds and bond-lengths characteristic of stereoactive lone-pair behavior of Pb2+. Four (AgCl6) octahedra link by sharing corners to form an [Ag4Cl18] cluster, and these clusters link by sharing corners to form a three-dimensional chequerboard arrangement, with [Pb4 (OH)(2) F2 Cl18] clusters filling the interstices. The structure of bideauxite is not related to those of the paragenetically related minerals boleite and pseudoboleite.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
