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M. Weil, M. Shirkhanlou, T. Stürzer:
"Phase Formation Studies of Lead(II) Copper(II) Oxotellurates: The Crystal Structures of Dimorphic PbCuTeO5, PbCuTe2O6, and [Pb2Cu2(Te4O11)](NO3)2";
Zeitschrift für Anorganische und Allgemeine Chemie, - (2019), 645; S. 347 - 353.

Two modifications of the oxotellurate(VI) PbCuTeO5 were
isolated as single crystals from product mixtures obtained from solid
state reactions, whereas single crystals of the oxotellurates(IV)
PbCuTe2O6 and [Pb2Cu2(Te4O11)](NO3)2 were grown under hydrothermal
conditions. The crystal structures of all compounds comprise of
characteristic coordination polyhedra, viz. nearly square [CuO4] plaquettes
for divalent copper, octahedral [TeO6] units for hexavalent tellurium,
trigonal-pyramidal [TeO3] and bisphenoidal [TeO4] groups for
tetravalent tellurium, and distorted [PbOx] polyhedra for divalent lead. PbCuTeO5 is dimorphic and crystallizes in a monoclinic and a triclinic
modification, related by a translationengleiche group-subgroup relation
of index 2. PbCuTe2O6 represents the ideal composition of the rare
mineral choloalite. The characteristic feature of the crystal structure of
[Pb2Cu2(Te4O11)](NO3)2 is its layered set-up, comprised of cationic
[Pb2Cu2(Te4O11)]2+ ribbons (width approximately 6.7 Å) sandwiched
between nitrate anions that are only weakly bound to the cationic layers.

http://dx.doi.org/10.1002/zaac.201800262