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

L. Balloch, A.M. Drummond, P. Garcia-Alvarez, D.V. Graham, A.R. Kennedy, J. Klett, R.E. Mulvey, C.T. O'Hara, P.J.A. Rodger, Iain David Rushworth

Research output: Contribution to journalArticle

16 Citations (Scopus)

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.
LanguageEnglish
Pages6934-6944
Number of pages10
JournalInorganic Chemistry
Volume48
Issue number14
DOIs
Publication statusPublished - 21 May 2009

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cubane
Metals
Atoms
metals
Molecules
atoms
molecules
Alkali Metals
Ladders
Hexanes
ladders
alkali metals
Anions
nitroxyl
insertion
Nuclear magnetic resonance
phenyllithium
anions
nuclear magnetic resonance
Electrons

Keywords

  • single electron reduction
  • anionic
  • alkali metal
  • TEMPO

Cite this

Balloch, L. ; Drummond, A.M. ; Garcia-Alvarez, P. ; Graham, D.V. ; Kennedy, A.R. ; Klett, J. ; Mulvey, R.E. ; O'Hara, C.T. ; Rodger, P.J.A. ; Rushworth, Iain David. / Structural variations within group 1 (Li-Cs)(+)(2,2,6,6-tetramethyl-1-piperidinyloxy)(-) complexes made via metallic reduction of the nitroxyl radical. In: Inorganic Chemistry. 2009 ; Vol. 48, No. 14. pp. 6934-6944.
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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.",
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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.; Drummond, A.M.; Garcia-Alvarez, P.; Graham, D.V.; Kennedy, A.R.; Klett, J.; Mulvey, R.E.; O'Hara, C.T.; Rodger, P.J.A.; Rushworth, Iain David.

In: Inorganic Chemistry, Vol. 48, No. 14, 21.05.2009, p. 6934-6944.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Structural variations within group 1 (Li-Cs)(+)(2,2,6,6-tetramethyl-1-piperidinyloxy)(-) complexes made via metallic reduction of the nitroxyl radical

AU - Balloch, L.

AU - Drummond, A.M.

AU - Garcia-Alvarez, P.

AU - Graham, D.V.

AU - Kennedy, A.R.

AU - Klett, J.

AU - Mulvey, R.E.

AU - O'Hara, C.T.

AU - Rodger, P.J.A.

AU - Rushworth, Iain David

N1 - 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.

PY - 2009/5/21

Y1 - 2009/5/21

N2 - 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.

AB - 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.

KW - single electron reduction

KW - anionic

KW - alkali metal

KW - TEMPO

UR - http://dx.doi.org/10.1021/ic900609e

U2 - 10.1021/ic900609e

DO - 10.1021/ic900609e

M3 - Article

VL - 48

SP - 6934

EP - 6944

JO - Inorganic Chemistry

T2 - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 14

ER -