Elektrochemische Synthesen, XIV [1] Radikalkation-Salze des Naphthalins / Electrochemical Syntheses, XIV [1]. Radical Cation Salts of Naphthalene

Abstract By anodic oxidation of naphthalene in H 2 CCl 2 /O.O2m Bu 4 NPF 6 at -45 °C dark red-violet crystals of (C 10 H 8 ) 2 PF 6 can be obtained by electrocrystallisation. They are stable at low temperatures, however, decompose on warming. In solution and in the polycrystalline state these radical cation salts show only narrow e.p.r. signals without h.f.s. The specific conductivity of a polycrystalline pellet at room temperature was determined to be 0.12 ±0.046 Ohm -1 cm -1 . The structure determination of (C 10 H 8 ) 2 PF 6 yielded the tetragonal space group P4 2 /n, Z = 2, a = b = 1156(2), c = 640(1) pm. Patterson synthesis and difference Fourier analyses showed the compound to have a columnar stacking of C 10 H 8 units the long molecular axes of which are twisted alternately by 90° around a screw axis in c-direction, and the molecular planes of which are 320 pm apart. The PF 6 - ions have four nearest C 10 H 8 neighbours lying in pairs in parallel planes 63 pm above and below that plane of PF 6 - perpendicular to the c-axis and containing a PF 4 group. This is the first established case for a columnar structure of a pure hydrocarbon radical cation. (C 10 H 8 ) 2 AsF 6 is isomorphous.