Synthesis, Structure, and Magnetism of Tris(amide) [Ln{N(SiMe 3 ) 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(NR 2 ) 3 (R=SiMe 3 ) 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 2 ) 3 ] complexes not only for the traditional Tm 2+ ion and the configurational crossover ions, Nd 2+ and Dy 2+ , but also for the non‐traditional Gd 2+ , Tb 2+ , Ho 2+ , and Er 2+ 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 Dy 2+ complex, [K(crypt)][Dy(NR 2 ) 3 ], has a higher magnetic moment than previously observed for any monometallic complex: 11.67 μ B .