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 Ln2+ 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 Ln2+ 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 4fn5d1 configurations for Ln2+ 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 μB. Assumption broken: A new series of Ln2+ complexes has been synthesized overturning previous generalizations in rare‐earth metal reduction chemistry: that amide ligands do not form isolable complexes of the highly reducing non‐traditional Ln2+ ions, and that yttrium is a good model for the late lanthanides in these reductive reactions.