The Ln[N(SiMe
3)
2]
3/K dinitrogen reduction system,
which mimicks the reactions of the highlyreducing divalent ions Tm(II), Dy(II), and Nd(II), has been explored
with the entire lanthanide series anduranium to examine its generality and to correlate the observed reactivity
with accessibility of divalentoxidation states. The Ln[N(SiMe
3)
2]
3/K reduction of dinitrogen provides access from readily available startingmaterials to the formerly rare class of M
2(
-
2:
2-N
2) complexes, {[(Me
3Si)
2N]
2(THF)Ln}
2(
-
2:
2-N
2),
1,that had previously been made only from TmI
2, DyI
2, and NdI
2 in the presence of KN(SiMe
3)
2. This LnZ
3/alkali metal reduction system provides crystallographically characterizable examples of
1 for Nd, Gd, Tb,Dy, Ho, Er, Y, Tm, and Lu. Sodium can be used as the alkali metal as
well as potassium. These compoundshave NN distances in the 1.258(3) to 1.318(5) Å range consistent
with formation of an (N=N)
2- moiety.Isolation of
1 with this selection of metals demonstrates that the Ln[N(SiMe
3)
2]
3/alkali metal reaction canmimic divalent lanthanide reduction chemistry
with metals that have calculated Ln(III)/Ln(II) reductionpotentials ranging from -2.3 to -3.9 V vs NHE. In the case of Ln = Sm,
which has an analogous Ln(III)/Ln(II) potential of -1.55 V, reduction to the stable divalent tris(amide) complex, K{Sm[N(SiMe
3)
2]
3}, isobserved instead of dinitrogen reduction. When the metal is La, Ce, Pr, or U, the first crystallographicallycharacterized examples of the tetrakis[bis(trimethylsilyl)amide] anions, {M[N(SiMe
3)
2]
4}
-, are isolated asTHF-solvated potassium or sodium salts. The implications of the LnZ
3/alkali metal reduction chemistry onthe mechanism of dinitrogen reduction and on reductive lanthanide chemistry in general are discussed.