Unstable intermediates. Part CLX. An electron spin resonance study of PCl4, PCl5–, PCl62–, and PCl6 radicals in irradiated phosphorus pentachloride
Abstract
Exposure of phosphorus pentachloride (PCl4+ PCl6–) to 60Co γ-rays at 77 K gave PCl4 and PCl5– radicals in comparable yields, together with a species thought to be PCl62– in lower yield. The isotropic 31P hyperfine coupling increases in this order (ca. 1 310 G, 1 617 G, and 1 815 G respectively). At 77 K PCl4 has two inequivalent chloride ligands (Aisoca. 35 G and 0 G respectively). The PCl5– species exhibited a smaller, poorly resolved, splitting interpreted as coupling to four equivalent chloride ligands. The species thought to be PCl62– also exhibited a multiple splitting from several chloride ligands but overlap of features made accurate assessment impossible.
Similar spectra for PCl4 and PCl5– radicals were obtained from solutions in carbon tetrachloride and toluene, in which PCl5 molecules are present, but the outer features assigned to PCl62– were absent.
Well resolved central features obtained from the pure material indicated hyperfine coupling to one phosphorus and two equvalent chlorine nuclei. This species is thought to be a strongly distorted PCl6 radical.