Structural variations within group 1 (Li-Cs)(+)(2,2,6,6-tetramethyl-1-piperidinyloxy)(-) complexes made via metallic reduction of the nitroxyl radical

Balloch, L. and Drummond, A.M. and Garcia-Alvarez, P. and Graham, D.V. and Kennedy, A.R. and Klett, J. and Mulvey, R.E. and O'Hara, C.T. and Rodger, P.J.A. and Rushworth, Iain David (2009) Structural variations within group 1 (Li-Cs)(+)(2,2,6,6-tetramethyl-1-piperidinyloxy)(-) complexes made via metallic reduction of the nitroxyl radical. Inorganic Chemistry, 48 (14). pp. 6934-6944. ISSN 1520-510X (http://dx.doi.org/10.1021/ic900609e)

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Abstract

Treatment of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) with a group 1 metal (Li, Na, K, Rb, or Cs), resulted in the reduction of this important radical to the TEMPO− anion-the first examples of elemental-metal single electron reduction of the radical to its anionic form. The synthesis and characterization of seven alkali metal TEMPO− complexes are reported. A variety of structural motifs are encountered depending on the choice of metal and/or solvent. (THF)2·[Li+(TEMPO−)]4 1 crystallized from THF as a cyclic (Li4O4) molecule. Two Li centers are stabilized by coordination to a THF molecule; the others by intramolecular coordination to NTEMPO atoms. [(THF)·Na+(TEMPO−)]4 2 exists as a distorted cubane where each Na center is coordinated to a THF molecule. No appreciable Na−NTEMPO coordination is observed. [(THF)2·Na+3(TEMPO−)2(OH)]2 3 was serendipitously prepared and exists as a distorted bis(cubane). It is envisaged that 3 is formed from 2 by insertion of a (Na-OH)2 double bridge into its framework. [Na+4(μ3-TEMPO−)2(μ2-TEMPO−)2(TMEDA)2] 4, adopts a four-runged ladder structure, whereby the two outer Na centers are coordinated to TMEDA, in addition to two μ2-O and a N atom. The inner metal atoms are bound to three μ3-O atoms and a N atom. [(THF)·K+(TEMPO−)]4 5 resembles the motif found for 2; however, presumably because of the larger size of the metal, K−NTEMPO interactions are present in 5. The asymmetric unit of [(TMEDA)·Rb+2(TEMPO−)2]2 6 comprises a Rb4O4 cubane with half a molecule of TMEDA coordinated to each metal. From a supramolecular perspective, 6 exists as a polymeric array of cubane units connected by TMEDA bridges. Completing the series, [Cs+(TEMPO)]∞ 7 crystallizes from hexane to form a donor-free polymeric complex. Complexes 1, 2, and 4−7 are soluble in D8-THF solution, and their NMR spectra are reported. The solution structures in donor solvent appear virtually identical.

ORCID iDs

Balloch, L., Drummond, A.M., Garcia-Alvarez, P., Graham, D.V., Kennedy, A.R. ORCID logoORCID: https://orcid.org/0000-0003-3652-6015, Klett, J., Mulvey, R.E. ORCID logoORCID: https://orcid.org/0000-0002-1015-2564, O'Hara, C.T., Rodger, P.J.A. and Rushworth, Iain David ORCID logoORCID: https://orcid.org/0000-0002-8440-412X;
  • Item type:Article
    ID code:16933
    Dates:
    Date
    Event
    21 May 2009
    Published
    Notes:Strathprints' policy is to record up to 8 authors per publication, plus any additional authors based at the University of Strathclyde. More authors may be listed on the official publication than appear in the Strathprints' record.
    Subjects:Science > Chemistry
    Department:Faculty of Science > Pure and Applied Chemistry
    Depositing user: Strathprints Administrator
    Date deposited:15 Apr 2010 15:32
    Last modified:11 Nov 2024 09:25
    URI:https://strathprints.strath.ac.uk/id/eprint/16933
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