Examination of Structure and Bonding in 10-Coordinate Europium and Americium Terpyridyl Complexes.

M(TpyNO)(NO)(HO)·THF (M = La, Nd, Sm, Eu, Tb, Am; TpyNO = 4'-nitrophenyl terpyridyl) have been prepared from the reaction of M(NO)· nHO with TpyNO in THF. Structural analysis shows that the metal centers are 10-coordinate, providing the first example of Am with this coordination number. Further spectroscopic and theoretical evaluation of these complexes reveals utilization of the 5f orbitals in bonding in the Am complex. Comparison of Nd-L, Eu-L, and Am-L bond distances demonstrates that some caution should be taken in comparing Eu versus Am in extraction experiments.