Electrochemical reduction of rare-earth chelates with certain ?-diketones

Abstract

Chelates of a number of lanthanides (Pr, Eu, Tb, Dy, Er, Tm, Yb) and certain other metals (Cu, Ni, Co, Tl) with the β-diketones dipivaloylmethane and trifluoroacetylcamphor are reduced electrochemically for the first time in aprotic medium (DMF). The nature of the lowest unoccupied molecular orbital, into which the first electron enters, is demonstrated to be centered on the ligand and not the metal. A difference is observed in the polarographic behavior of the cerium subgroup complexes (Pr, Eu), which are reduced in one step, and those of the yttrium subgroup, which exhibit two waves (Tb, Er, Yb) of a distinctly doubled wave (Tm, Dy).