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

A new series of Ln 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 ions, and that yttrium is a good model for the late lanthanides in these reductive reactions. Reduction of Ln(NR ) (R=SiMe ) 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(NR ) ] complexes not only for the traditional Tm ion and the configurational crossover ions, Nd and Dy , but also for the non-traditional Gd , Tb , Ho , and Er ions. Crystallographic data as well as UV/Vis, magnetic susceptibility, and density functional theory studies are consistent with the accessibility of 4f 5d configurations for Ln ions in this tris(silylamide) ligand environment. The Dy complex, [K(crypt)][Dy(NR ) ], has a higher magnetic moment than previously observed for any monometallic complex: 11.67 μ .