ESR Study of Radicals Formed by Irradiation of K2PtCl4 Single Crystals

Single crystals of K2PtCl4 irradiated at 77°K show two groups of ESR lines, one belonging to a radical giving rise to hyperfine interaction with two equivalent platinum nuclei and the second from a radical giving hyperfine interaction with one platinum and three chlorine nuclei. On the basis of the observed g, A (195Pt), and A (35, 37Cl) tensors, it is suggested that these species are [(PtCl4)2]3− and [PtCl3]2−, respectively, with d15 and d9 configurations. On warming to 125°K part of the dimeric radical is converted to a new species whose ESR parameters are consistent with the structure [PtCl5]2+ with a d7 configuration. The structures of these radicals are discussed.