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
JF - Inorganic Chemistry
SN - 0020-1669
IS - 14
ER -