Complex Fluorides of Tetravalent Cobalt

Abstract

A new compound, Rb 2 CoF 6 has been prepared. Rb 2 CoF 6 and Cs 2 CoF 6 both have the cubic K 2 PtCl 6 structure with a = 8.460(3) Å and d(Co—F) = 1.65(5) Å for Rb 2 CoF 6 and a = 8.914(2) Å and d(Co—F) = 1.73(5) Å for Cs 2 CoF 6 . The temperature dependent magnetic susceptibilities of Rb 2 CoF 6 and Cs 2 CoF 6 are reported and interpreted. The data are consistent with the Co IV having a 2 T 2 ground state and both Rb 2 CoF 6 and Cs 2 CoF 6 exhibiting complex ferromagnetic behavior with a Curie temperature above ambient.