Unusual Disordering of Potassium Ions in the Structures of Cluster Rhenium Thiohalides K3[Re6S7Br7] and K4[Re6S8Cl6]

New cluster compounds — rhenium and potassium thiohalides K₃Re₆S₇Br₇ (I) and K₄Re₆S₈Cl₆ (II) — have been synthesized. Their crystal structures have been determined by single crystal X-ray diffraction. The compounds are monoclinic; (I): space group P2₁/c, a = 9.32(1) Å, b = 13.528 Å, c = 12.413 Å, β = 110.21°, Z = 2, R = 0.038; (II): space group C2/m, a = 10.614 Å, b = 17.268 Å, c = 10.448 Å, β = 110.755°, Z = 2, R = 0.042. In both structures, the potassium ions are considerably distorted. The occupancies of the potassium sites are 0.17-0.34 (I) and 0. 01-0.26 (II), correlating well with the coordination numbers (c.n. 7-10 and 2-7 for I and II, respectively). In I, adjacent positions of potassium atoms are aggregated into discrete tetrahedral and angular clusters; in II, the individual (four-and six-membered) cyclic clusters of potassium sites are present along with bent chains of vertex-and edge-sharing tetrahedral “potassium clusters.” The shortest K-K distances in these “clusters” vary from 1.31 Å to 1.54 Å (I) and from 0.66 Å to 1.65 Å (II). The “instability” of the potassium site suggests that I and II are ion conductors.Original Russian Text Copyright © 2004 by S. F. Solodovnikov, S. S. Yarovoi, Yu. V. Mironov, A. V. Virovets, and V. E. Fedorov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 909–917, September–October, 2004.