The First Palladium Tin Selenide: Pd 7 Sn 2 Se 9.85

Pd 7 Sn 2 Se 9+x with x = 0.5‐0.85 were prepared by heating the elements at 750 °C in silica ampoules under argon atmosphere. The crystal structures were determined by single crystal X‐ray methods. The selenides crystallize in a new hexagonal structure type (Pd 7 Sn 2 Se 9.85 : P 6 3 / mmc , Z = 2, a = 7.297(2), c = 16.314(3) Å) with palladium atoms in six‐fold octahedral and four‐fold square coordination of selenium. Layers of isolated PdSe 6 octahedra are connected along [001] by face‐ and edge‐sharing PdSe 4/2 squares, whose Se atoms form anti‐cuboctahedra, each centered by selenium atoms with fractional occupations from x = 0.513(5) up to x = 0.847(6). The lattice parameter c increases linearly with x from 16.167(3) Å for Pd 7 Sn 2 Se 9.51 to 16.314(3) Å in Pd 7 Sn 2 Se 9.85 . Tin is bonded to three selenium and three palladium atoms, respectively, both together form a distorted trigonal antiprism. Measurements of the electrical conductivity and the magnetic susceptibility reveals metallic Pauli‐paramagnetic behavior. The electronic charge distribution based on quantum mechanical calculations within the AIM theory is discussed. A mechanism based on the balance between increasing bonding energy and reorganization of charges is proposed and suspected to be a reason for the fractional occupation of one selenium site.