Elektronentransfer und Ionenpaar‐Bildung. 40. Mitteilung . Einkristall‐Struktur von Bis(Natrium‐1,1′‐Biphenyl‐2‐thiolat‐Diglyme): Ein Zwischenprodukt der reduktiven Ringöffnung von Dibenzothiophen

Electron Transfer and Ion Pair Formation Single Crystal Structure of Bis(sodium 1,1′‐biphenyl‐2‐thiolate‐diglyme): An Intermediate in the Reductive Ring Opening of Dibenzothiophene On Na‐metal reduction of dibenzothiophene, the five‐membered sulfur ring opens to form a colorless 1,1′‐biphenyl‐2‐thiolate sodium salt, which, according to its single‐crystal structure determination, is a dimer containing a four‐membered, twice diglyme‐solvated ring (diglyme···Na ⊕ ⊖ SR) 2 . Additional measurements provide the following information: cyclic voltammetry in aprotic MeCN solution shows one quasi‐reversible electron transfer at E   1/2 Red= −2.58 V. The dibenzothiophene radical anion can be generated in aprotic THF solution at a K mirror and characterized by an 81‐line ESR spectrum and its simulation. This blue species is also the first UV/VIS detectable one before the solution changes via green (due to blue + yellow color mixing) to yellow, yielding across an isosbestic point a second and diamagnetic compound. All of the above results suggest a consecutive two‐electron reduction followed by an intersystem protonation, M + (e ⊖ ) → M .⊖ (blue) + (e ⊖ ) → (M ⊖⊖ , yellow?) + (H ⊕ ) → MH ⊖ (colorless), to yield the crystallized and structurally characterized reaction intermediate. The diglyme‐solvated sodium‐salt dimer provides a basis for a quantum‐chemical discussion of some facets of the most likely microscopic reduction pathway.