CRYSTAL STRUCTURE OF CS2PDI4 · I2 AND PRESSURE-INDUCED CHEMICAL REACTION TO CS2PDI6
H.-L. Keller1, B. Schüpp1, P. Heines1, H.-J. Hesse2
1 Inorganic Chemistry, University of Dortmund,
Otto-Hahn-Str. 6, D - 44227 Dortmund
2 Experimental Physics, University of Paderborn, Warburger
Str. 100, D - 33098 Paderborn
Only few essays about ternary palladiumiodides have been published so far. We have been interested in the structural chemistry of palladiumhalides and have thus also studied palladiumiodides. Hydrothermal synthesis [1,2] seemed to be a promising preparative technique to us, because we have already managed to synthesize some new compounds in the Cs - Pd - Cl system using this method. Recently we were able to synthesize from aqueous HI solution two compounds with the same empirical formula, Cs2PdI4 · I2 and Cs2PdI6, with palladium in the oxidation state +2 respectively +4 by using this method.
Single crystal X-ray determination of Cs2PdI6 confirmed the results of powder data [3], i.e. Cs2PdI6 is isotypic to K2PtCl6 [4]. Cs2PdI6 crystallizes in space group Fm3_m (No. 225) with lattice parameter a = 11.332 (1) A (single crystal).
Cs2PdI4 · I2 single crystals show tetragonal symmetry, space group I 4/mmm (No. 139) with lattice parameters a = 8.987 (1) b and c = 9.240 (1) b. In the crystal structure we found square-planar [PdI4]2- groups as well as neutral I2 molecules. The crystal structure resembles the Cs2Au(I)Au(III)Cl6 [5,6] with the main difference being the substitution of [Au(I)Cl2]- dumbbell by an I2 molecule. The changing sequence of [PdI4]2- and I2 groups in the direction of [001] shows the possibility to reach the Cs2PdI6 structure with disintegration of the I2 molecules and valence change Pd2+ to Pd4+ by pressure. Further results will be discussed at the conference.