X-Ray, n.m.r., and theoretical studies of the structures of (ethylthio)bullvalene

Abstract

The structure of (ethylthio)bullvalene has been determined in solution and solid state. Whereas the structure of the title compound in the crystal is 4-(ethylthio)tricyclo[3.3.2.0]deca-3,6,9-triene, in solution a mixture of the 4-(ethylthio)-(15%) and 3-(ethylthio)-bullvalene (85%) has been detected. The dynamics of the valence tautomerism has been studied by variable temperature ¹H n.m.r. spectroscopy. A comparison between the experimentally determined thermodynamic and kinetic quantitites of the valence tautomerism with MINDO/3, MNDO, and force-field calculations shows very good agreement between theory and experiment.