Condensed [OPr4]10+ and Discrete [AsO3]3–Ψ1-Tetrahedra in Pr5O4Cl[AsO3]2

Abstract

The oxide chloride arsenite Pr5O4Cl[AsO3]2 was obtained as green crystals as a by-product of the synthesis of PrOTAs oxide arsenides (T = late transition metal), starting from Pr6O11, a transition metal oxide, arsenic, and an NaCl/KCl flux. Pr5O4Cl[AsO3]2 crystallizes with the monoclinic Nd5O4Cl[AsO3]2-type structure, space group C2/m. The structure was refined from single-crystal diffractometer data: a = 12.4943(15), b = 5.6884(13) c = 9.0776(19) Å , β = 116.61(1)°, R(F) = 0.0264, wR(F2) = 0.0509, 542 F2 values, and 52 variables. It is built up from corrugated layers of edge- and corner-sharing [OPr4]10+ tetrahedra, which are connected via chloride anions. The space between the layers is filled by these Cl− and discrete arsenite anions [AsO3]3− with lone pairs pointing towards each other. The network of condensed [OPr4]10+ tetrahedra is compared with the different arrays in the oxide pnictides α-PrOZnP, and in β -PrOZnP. Arsenic lone pair energy bands, main interactions, and the spatial distribution were identified precisely using density functional theory (DFT). Among the three crystallographically different sites for praseodymium, one was found non-magnetic in these calculations.