Bis([5]trovacenyl)dichalcogenides: Synthesis, Structure, and Study of Intramolecular Communication

The paramagnetic bis(5trovacenyl)dichalcogenides(η 7 ‐C 7 H 7 )V(η 5 ‐C 5 H 4 ‐ E – E –η 5 ‐C 5 H 4 )V(η 7 ‐C 7 H 7 ) 2 ·· ( E = S), 3 ·· ( E = Se), and 4 ·· ( E = Te) were prepared by a novel path in which the elemental chalcogen atoms serve as suppliers of the hetero‐atoms and as oxidants in the final step. Compounds 2 ·· and 4 ·· were analyzed by single‐crystal X‐ray diffraction analyses. Cyclic voltammetry revealed that redox splitting in 2 ·· – 4 ·· is not resolved, i.e. the potential difference of successive redox steps is less than 70 mV. Compound 2 ·· was studied in detail by EPR spectroscopy and magnetic susceptometry. EPR spectroscopy clearly demonstrated spin exchange coupling of two unpaired electrons, which reside in vanadium centered orbitals ( 51 V, I = 7/2), | J EPR ( 2 ·· )| = 0.65 cm –1 . The considerably larger value J χ ( 2 ·· ) = –1.36 cm –1 was obtained from magnetic susceptometry. This apparent discrepancy is discussed, based on a comparison of the spacers –S–S–,–CH 2 –CH 2 –, and –C(CH 3 ) = C(CH 3 )–.