Expanding Dinitrogen Reduction Chemistry to Trivalent Lanthanides via the LnZ3/Alkali Metal Reduction System: Evaluation of the Generality of Forming Ln2(
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- 作者：William J. Evans ; David S. Lee ; Daniel B. Rego ; Jeremy M. Perotti ; Stosh A. Kozimor ; Ericka K. Moore ; and Joseph W. Ziller
- 刊名：Journal of the American Chemical Society
- 出版年：2004
- 出版时间：November 10, 2004
- 年：2004
- 卷：126
- 期：44
- 页码：14574 - 14582
- 全文大小：187K
- 年卷期：v.126,no.44(November 10, 2004)
- ISSN：1520-5126
文摘
The Ln[N(SiMe3)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(SiMe3)2]3/K reduction of dinitrogen provides access from readily available startingmaterials to the formerly rare class of M2(
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2:2-N2) complexes, {[(Me3Si)2N]2(THF)Ln}2(-2:2-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 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(SiMe3)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(SiMe3)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(SiMe3)2]4}-, are isolated asTHF-solvated potassium or sodium salts. The implications of the LnZ3/alkali metal reduction chemistry onthe mechanism of dinitrogen reduction and on reductive lanthanide chemistry in general are discussed.
-2:2-N2) complexes, {[(Me3Si)2N]2(THF)Ln}2(-2:2-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 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(SiMe3)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(SiMe3)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(SiMe3)2]4}-, are isolated asTHF-solvated potassium or sodium salts. The implications of the LnZ3/alkali metal reduction chemistry onthe mechanism of dinitrogen reduction and on reductive lanthanide chemistry in general are discussed.