The structure of 1,6,6aλ4‐trithiapentalene and substituted 1,6,6aλ4‐trithiapentalenes studied by means of NMR spectroscopy

Abstract 13C NMR spectra of unsubstituted 1,6,6aλ4‐trithiapentalene and a series of methyl and phenyl substituted 1,6,6aλ4‐trithiapentalenes have been recorded. The spectra have been assigned by comparison with 1H NMR data based on coupling constants from undecoupled spectra. From the chemical shift of C‐3a it is concluded that the double bond character of the C‐3a—S‐6a is low. The relaxation times for C‐2 and C‐3 only show small differences; this seems not to be in favour of a fast interconversion between two thiocarbonyl forms. The NMR data obtained seem thus to be in accordance with a bicyclic naphthalene‐like structure with ten delocalised π‐electrons.