TY  - JOUR
A1  - Bock, Hans
A1  - Hänel, Peter
T1  - Elektronentransfer und Ionenpaar-Bildung, 27 [1, 2]. Darstellung von Semichinon-Ionenpaaren durch Reduktion von Chinonen mit Tetraalkylammonium-boranat in aprotischen Lösungen: 1,10-Phenanthrolin-5,6-dion
T1  - Electron transfer and ion pairing, 27 [1, 2]. Preparation of semiquinone ion pairs by reduction of quinones using tetraalkylammonium boranate in aprotic salt solutions: 1,10-phenanthrolin-5,6-dione
T2  - Zeitschrift für Naturforschung, B
N2  - Ion pairs of 1,10-phenanthrolin-5,6-dione radical anion [M · ⊖Me⊕n] ·⊕(n−1) with Me⊕n = Mg⊕⊕, Ca⊕⊕, Sr⊕⊕, Zn⊕⊕, Cd⊕⊕, Pb⊕⊕ and La⊕⊕⊕ are advantageously prepared in aprotic DMF solution containing appropriate metal salts Me⊕nX⊖ by using the ‘mild’ single-electron reducing agent tetra(n-butyl)ammonium-boranate R4N⊕BH4⊖ . For comparison, the ‘naked’ radical anion with the largely interaction-free [K⊕(2.2.2)-cryptand]⊕ counter cation is chosen, which is formed on reduction with potassium in THF solution of (2.2.2)-cryptand. Addition of excess Na⊕[B(C6H5)4]⊖ to the reduction solution only yields a solvent-separated ion pair (M · ⊖)DMF ··· (Na⊕)DMF, whereas in the presence of multiply charged counter cations Me⊕n the respective contact ion pair radical cations [M · ⊖Me⊕n] · ⊕(n−1) are formed. Their g values decrease with increasing nuclear charge of Me⊕n and their metal-s-spin densities increase with the effective counter cation charge n⊕/rMe⊕n. The ESR /ENDOR data recorded suggest Me⊕n complexation by the δ⊖OC -COδ⊖ chelate tongs and the ion pair stability, which is modified by the dielectric properties of the solvent used, may be rationalized by the Coulombic attraction between the radical anion M · ⊖ and the counter cations Me⊕n.
KW  - 1.10-Phenanthrolin-5,6-dione
KW  - Reduction by R4N®BH4e
KW  - Contact Ion Pairs
KW  - ESR/ENDOR Spectra
Y1  - 2014
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/80932
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-809322
SN  - 1865-7117
SN  - 0932-0776
VL  - 47.1991
IS  - 2
SP  - 288
EP  - 300
PB  - Verlag der Zeitschrift für Naturforschung
CY  - Tübingen
ER  -