Electrochemical studies of tris(cyclopentadienyl)thorium and uranium complexes in the +2, +3, and +4 oxidation states

Abstract

Electrochemical measurements on tris(cyclopentadienyl)thorium and uranium compounds in the +2, +3, and +4 oxidation states are reported with C₅H₃(SiMe₃)₂, C₅H₄SiMe₃, and C₅Me₄H ligands. The reduction potentials for both U and Th complexes trend with the electron donating abilities of the cyclopentadienyl ligand. Thorium complexes have more negative An(III)/An(II) reduction potentials than the uranium analogs. Electrochemical measurements of isolated Th(II) complexes indicated that the Th(III)/Th(II) couple was surprisingly similar to the Th(IV)/Th(III) couple in Cp′′-ligated complexes. This suggested that Th(II) complexes could be prepared from Th(IV) precursors and this was demonstrated synthetically by isolation of directly from UV-visible spectroelectrochemical measurements and reactions of with elemental barium indicated that the thorium system undergoes sequential one electron transformations.