WEAK OR UNSTABLE IODO COMPLEXES .I. HEXAIODO COMPLEXES OF LANTHANIDES

The extremely weak hexaiodo complexes of the trivalent lanthanides can be prepared as triphenylphosphonium or pyridinium salts by the reaction of the corresponding hexachloro salts with liquid anhydrous hydrogen iodide. These complexes dissociate in nonaqueous solvents even in the presence of excess iodide, and the solid salts are attacked by atmospheric moisture and oxygen. The internal transitions in the 4f shell are very similar to those of the corresponding hexachloro and hexabromo complexes. The metal-halogen frequencies in the vibronic and far-infrared spectra decrease by the amount expected with increase in halide mass. The electron-transfer spectra of hexaiodo complexes of Sm, Eu, Tm, and Yb are discussed and compared with those of the hexachloro and hexabromo complexes. © 1969, American Chemical Society. All rights reserved.