Raman spectroscopy of the N-N bond in rare earth dinitrogen complexes

Megan E. Fieser, David H. Woen, Jordan F. Corbey, Thomas J. Mueller, Joseph W. Ziller, William J. Evans

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Raman spectra have been collected on single crystals of over 20 different rare earth complexes containing reduced dinitrogen ligands to determine if these data will correlate with periodic properties or relative stability. Four types of complexes were examined: [(C5Me5)2Ln]2(μ-η22-N2), 1-Ln, [(C5Me4H)2(THF)Ln]2(μ-η22-N2), 2-Ln, [(C5H4Me)2Ln]2(μ-η22-N2), 3-Ln, and {[(Me3Si)2N]2(THF)Ln}2(μ-η22-N2), 4-Ln. Although each of the complexes contains a side-on bound dinitrogen ligand that is formally (N2)2-, the N-N bond distances determined by X-ray crystallography range from 1.088(12) to 1.305(6) Å. In the 4-Ln series (Ln = Gd, Tb, Dy, Ho, Er and Tm), the 1.26-1.31 Å N-N distances do not follow any periodic trends, but the Raman stretching frequencies for Gd-Tm were found to decrease regularly with decreasing atomic number and increasing Lewis acidity of the metal. Similar correlations can be seen with the late metals in complexes of the other series, 1-Ln, 2-Ln and 3-Ln, but exceptions exist, particularly for the larger metals. Comparisons between the several types of complexes as a function of ligand were more complicated and variations in stretching frequency as a function of L in the {[(Me3Si)2N]2Y(L)}2(μ-η22-N2) substituted versions of 4-Y did not give trends consistent with bond distances or Gutmann donor numbers.

Original languageEnglish (US)
Pages (from-to)14634-14644
Number of pages11
JournalDalton Transactions
Issue number37
StatePublished - 2016

Bibliographical note

Funding Information:
We thank the U.S. National Science Foundation for support of this research under Grant CHE-1265396 as well as Dr Dmitry A. Fishman in the UCI Laser Spectroscopy Facility for assistance with Raman spectroscopy.

Publisher Copyright:
© The Royal Society of Chemistry 2016.


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