Examination Of Structure And Bonding In 10-Coordinate Europium And Americium Terpyridyl Complexes

M(TpyNO(2))(NO3)(3)(H2O).THE (M = La, Nd, Sm, Eu, Tb, Am; TpyNO(2) = 4'-nitrophenyl terpyridyl) have been prepared from the reaction of M(NO3)(3)center dot nH(2)O with TpyNO(2) in THF. Structural analysis shows that the metal centers are 10-coordinate, providing the first example of Am-III with this coordination number. Further spectroscopic and theoretical evaluation of these complexes reveals utilization of the 5f orbitals in bonding in the AmIII complex. Comparison of Nd L, Eu L, and Am L bond distances demonstrates that some caution should be taken in comparing Eu-III versus Am-III in extraction experiments.