Contributions on crystal chemistry and thermal behaviour of anhydrous phosphates. XXIV. Preparation, crystal structure, and properties of copper(II) indium(III) orthophosphate Cu3In2[PO4](4) [German]

摘要

Crystals of Cu3In2[PO4](4) were grown by chemical vapour transport (temperature gradient 1273 K --> 1173 K) using chlorine as transport agent. The mixed metal phosphate forms a new structure type (P2(1)/c, Z = 2, a = 8.9067(6), b = 8.8271(5), c = 7.8815(5) Angstrom, beta = 108.393(5)degrees, 13 atoms in asymmetric unit, 2549 unique reflections with F-o > 4 sigma, 116 variables, R(F-2)= 0.065). The crystal structure shows a hexagonal closest packing of [PO4](3-) tetrahedra. Close-packed layers parallel (1 0 -1) are stacked according to the sequence A, B, A ', B ', A. The octahedral interstices in this packing are completely occupied by two In3+, one (Cu1)(2+) and a "dumb bell" (Cu2)(2)(4+). In the latter case four of the six phosphate groups that belong to this octahedral void act as bi-dentate ligands, thus forming dimers [(Cu-2)(2)O-10] with d(Cu-Cu) = 3.032 Angstrom. Cu3In2[PO4](4) is paramagnetic (mu (eff) = 1.89 mu (B), theta (P) = -16.9 K). The infrared and UV/Vis reflectance spectra are reported. The observed d-electron levels of the Cu2+ cations agree well with those obtained from angular overlap calculations. [References: 25]