ja046047s_si_009.cif (26.05 kB)
Expanding Dinitrogen Reduction Chemistry to Trivalent Lanthanides via the LnZ3/Alkali Metal Reduction System: Evaluation of the Generality of Forming Ln2(μ-η2:η2-N2) Complexes via LnZ3/K
dataset
posted on 2004-11-10, 00:00 authored by William J. Evans, David S. Lee, Daniel B. Rego, Jeremy M. Perotti, Stosh A. Kozimor, Ericka K. Moore, Joseph W. ZillerThe Ln[N(SiMe3)2]3/K dinitrogen reduction system, which mimicks the reactions of the highly
reducing divalent ions Tm(II), Dy(II), and Nd(II), has been explored with the entire lanthanide series and
uranium to examine its generality and to correlate the observed reactivity with accessibility of divalent
oxidation states. The Ln[N(SiMe3)2]3/K reduction of dinitrogen provides access from readily available starting
materials to the formerly rare class of M2(μ-η2:η2-N2) complexes, {[(Me3Si)2N]2(THF)Ln}2(μ-η2:η2-N2), 1,
that had previously been made only from TmI2, DyI2, and NdI2 in the presence of KN(SiMe3)2. This LnZ3/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 compounds
have NN distances in the 1.258(3) to 1.318(5) Å range consistent with formation of an (NN)2- moiety.
Isolation of 1 with this selection of metals demonstrates that the Ln[N(SiMe3)2]3/alkali metal reaction can
mimic divalent lanthanide reduction chemistry with metals that have calculated Ln(III)/Ln(II) reduction
potentials 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(SiMe3)2]3}, is
observed instead of dinitrogen reduction. When the metal is La, Ce, Pr, or U, the first crystallographically
characterized examples of the tetrakis[bis(trimethylsilyl)amide] anions, {M[N(SiMe3)2]4}-, are isolated as
THF-solvated potassium or sodium salts. The implications of the LnZ3/alkali metal reduction chemistry on
the mechanism of dinitrogen reduction and on reductive lanthanide chemistry in general are discussed.