Synthesis, Structure, and Magnetism of Tris(amide) [Ln{N(SiMe3)(2)}(3)](1-) Complexes of the Non-traditional+2 Lanthanide Ions

A new series of Ln(2+) complexes has been synthesized that overturns two previous generalizations in rare-earth metal reduction chemistry: that amide ligands do not form isolable complexes of the highly reducing non-traditional Ln(2+) ions, and that yttrium is a good model for the late lanthanides in these reductive reactions. Reduction of Ln(NR2)(3) (R=SiMe3) complexes in THF under Ar with M=K or Rb in the presence of 2.2.2-cryptand (crypt) forms crystallographically characterizable [M(crypt)][Ln(NR2)(3)] complexes not only for the traditional Tm2+ ion and the configurational crossover ions, Nd2+ and Dy2+, but also for the non-traditional Gd2+, Tb2+, Ho2+, and Er2+ ions. Crystallographic data as well as UV/Vis, magnetic susceptibility, and density functional theory studies are consistent with the accessibility of 4f(n)5d(1) configurations for Ln(2+) ions in this tris(silylamide) ligand environment. The Dy2+ complex, [K(crypt)][Dy(NR2)(3)], has a higher magnetic moment than previously observed for any monometallic complex: 11.67 mu(B).