Evaluating Electron-Transfer Reactivity of Complexes of Actinides in +2 and +3 Oxidation States by using EPR Spectroscopy.

The possibility that the relative reactivity of complexes of actinide metals in the +2 and +3 oxidation states could be investigated by examining reactions between AnIII and AnII species of Th and U with rare-earth metal reagents that provide EPR confirmation of electron transfer reactivity has been explored. Neither Cp''3 ThIII nor Cp''3 UIII will reduce Cp''3 LaIII or Cp'3 YIII (Cp'=C5 H4 SiMe3 , Cp''=C5 H3 (SiMe3 )2 ). However, both [K(2.2.2-cryptand)][Cp''3 ThII ] and [K(2.2.2-cryptand)][Cp''3 UII ] reduce Cp''3 LaIII and Cp'3 YIII to form [Cp''3 LaII ]1- and [Cp'3 YII ]1- , respectively, which were identified by EPR spectroscopy. The reverse reactions also occur which indicates that the reduction potentials are similar. [Cp''3 LaII ]1- reduces Cp'3 YIII and the reverse YII /LaIII combination also occurs. In both cases, the reactions generate EPR spectra indicative of multiple species in the mixtures of LaII and YII , which is consistent with ligand exchange and demonstrates that numerous heteroleptic complexes of these LnII ions exist.