TY - JOUR

T1 - Chloroxiphite Pb3CuO2(OH)2Cl2

T2 - Structure refinement and description in terms of oxocentred OPb4 tetrahedra

AU - Siidra, O. I.

AU - Krivovichev, S. V.

AU - Turner, R. W.

AU - Rumsey, M. S.

PY - 2008

Y1 - 2008

N2 - The crystal structure ofchloroxiphite, Pb3 CuO2 (OH)2 Cl2, from Merehead Quarry (monoclinic, P21/m, a = 6.6972(8), b = 5.7538(5), c = 10.4686(14) Å, β = 97.747(10)°, V = 399.72(8) Å3) has been refined to R1 = 0.041. The structure contains three symmetrically unique Pb sites and one Cu site. The strong distortion ofthe Pb2+ coordination polyhedra is due to the stereoactivity ofthe s2 lone electron pairs on the Pb2+ cations. The Cu-site is coordinated by four OH- groups to form an almost planar Cu(OH)4 square that is complemented by two apical Cl- anions, forming an elongated [Cu(OH)4Cl2] octahedron. Because ofthe large size and variability ofcoordination polyhedra around Pb2+ cations and the strength ofthe Me-O bonds in comparison to the Me-Cl bonds (Me = metal), it is convenient to describe the structure ofchloroxiphite in terms of oxocentred OPb4 tetrahedra. The O1 atom is tetrahedrally coordinated by four Pb2+ cations forming relatively short and strong O-Pb bonds. The OPb4 tetrahedra link together via common edges to form [O2Pb3]2+ double chains. The difference between chloroxiphite and other natural oxyhalides is the presence of Cu2+ cations which form an independent structural unit that links to units formed by OPb4 tetrahedra. In this sense, chloroxiphite can be considered as a modular structure consisting ofboth strong cation- and anion-centred units.

AB - The crystal structure ofchloroxiphite, Pb3 CuO2 (OH)2 Cl2, from Merehead Quarry (monoclinic, P21/m, a = 6.6972(8), b = 5.7538(5), c = 10.4686(14) Å, β = 97.747(10)°, V = 399.72(8) Å3) has been refined to R1 = 0.041. The structure contains three symmetrically unique Pb sites and one Cu site. The strong distortion ofthe Pb2+ coordination polyhedra is due to the stereoactivity ofthe s2 lone electron pairs on the Pb2+ cations. The Cu-site is coordinated by four OH- groups to form an almost planar Cu(OH)4 square that is complemented by two apical Cl- anions, forming an elongated [Cu(OH)4Cl2] octahedron. Because ofthe large size and variability ofcoordination polyhedra around Pb2+ cations and the strength ofthe Me-O bonds in comparison to the Me-Cl bonds (Me = metal), it is convenient to describe the structure ofchloroxiphite in terms of oxocentred OPb4 tetrahedra. The O1 atom is tetrahedrally coordinated by four Pb2+ cations forming relatively short and strong O-Pb bonds. The OPb4 tetrahedra link together via common edges to form [O2Pb3]2+ double chains. The difference between chloroxiphite and other natural oxyhalides is the presence of Cu2+ cations which form an independent structural unit that links to units formed by OPb4 tetrahedra. In this sense, chloroxiphite can be considered as a modular structure consisting ofboth strong cation- and anion-centred units.

KW - Chloroxiphite

KW - Crystal structure

KW - Lead oxyhalides

KW - Merehead

KW - Oxocentred tetrahedra

KW - UK

UR - http://www.scopus.com/inward/record.url?scp=64549108054&partnerID=8YFLogxK

U2 - 10.1180/minmag.2008.072.3.793

DO - 10.1180/minmag.2008.072.3.793

M3 - Article

AN - SCOPUS:64549108054

VL - 72

SP - 793

EP - 798

JO - Mineralogical Magazine

JF - Mineralogical Magazine

SN - 0026-461X

IS - 3

ER -