Structural and magnetic properties of some AgF + Salts

Abstract

New salts of the one-dimensional chain-cation (Ag−F)nn+ have been prepared, the structural and magnetic properties of which indicate that they are metallic. A single-crystal X-ray structure analysis of AgFBF4 has established a linear cationic chain, the two Ag−F interatomic distances, at 296 K, being 2.002(3) and 2.009(3) A. Magnetic susceptibility measurements on the poweder from 6 to 280 K show an approximately temperature-independent paramagnetism (χM∼180×10−6 emu mole−1) with no evidence of a Peierls transition in that range. Although the previously known salt, AgFAsF6, has a kinked cationic chain (with, at 166 K, Ag−F−Ag=143.1(1)o, F−Ag−F=175.8(1)o, Ag−F=1.994(2) and 2.001(2) A), it also exhibits temperature-independent paramagnetism from 280 down to 63 K, but a sharp drop in susceptibility below that temperature may signify a Peierls transition. AgFAuF6, which is probably isostructural with AgFAsF6, is similar to it magnetically. The salt AgFAuF4 probably contains a linear cationic chain, since it is isostructural with CuFAuF4, but the salt Ag(AuF4)2, like its relative Ag(AgF4)2, is a magnetically dilute paramagnet, the magnetic susceptibility of which departs very little from the Curie law between 6 and 280 K.