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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.
Original language | English |
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Pages (from-to) | 6934-6944 |
Number of pages | 10 |
Journal | Inorganic Chemistry |
Volume | 48 |
Issue number | 14 |
DOIs | |
Publication status | Published - 21 May 2009 |
Keywords
- single electron reduction
- anionic
- alkali metal
- TEMPO
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Dive into the research topics of 'Structural variations within group 1 (Li-Cs)(+)(2,2,6,6-tetramethyl-1-piperidinyloxy)(-) complexes made via metallic reduction of the nitroxyl radical'. Together they form a unique fingerprint.Projects
- 2 Finished
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ENANTIOSELECTIVE APPLICATIONS OF DESIGNER SYNERGIC REAGENTS (First Grant)
O'Hara, C. (Principal Investigator)
EPSRC (Engineering and Physical Sciences Research Council)
1/10/08 → 31/03/12
Project: Research
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"INVERSE" COORDINATION: A NEW DESIGN CONCEPT IN SUPRAMOLECULAR INORGANIC CHEMISTRY
Mulvey, R. (Principal Investigator)
EPSRC (Engineering and Physical Sciences Research Council)
1/10/06 → 31/03/10
Project: Research