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 An III and An II species of Th and U with rare‐earth metal reagents that provide EPR confirmation of electron transfer reactivity has been explored. Neither Cp’’ 3 Th III nor Cp’’ 3 U III will reduce Cp’’ 3 La III or Cp’ 3 Y III (Cp’=C 5 H 4 SiMe 3 , Cp’’=C 5 H 3 (SiMe 3 ) 2 ). However, both [K(2.2.2‐cryptand)][Cp’’ 3 Th II ] and [K(2.2.2‐cryptand)][Cp’’ 3 U II ] reduce Cp’’ 3 La III and Cp’ 3 Y III to form [Cp’’ 3 La II ] 1− and [Cp’ 3 Y II ] 1− , respectively, which were identified by EPR spectroscopy. The reverse reactions also occur which indicates that the reduction potentials are similar. [Cp’’ 3 La II ] 1− reduces Cp’ 3 Y III and the reverse Y II /La III combination also occurs. In both cases, the reactions generate EPR spectra indicative of multiple species in the mixtures of La II and Y II , which is consistent with ligand exchange and demonstrates that numerous heteroleptic complexes of these Ln II ions exist.