Ethenedithione (S=C=C=S): Does It Obey Hund's Rule?

Significantly higher in energy (24 kJ mol^-1 ) than the triplet ground state (³ Σ_g^- ) is the ¹ Δ_g state of ethenedithione (S=C=C=S), in agreement with Hund's rule. This result was obtained from high-level ab initio calculations. Thus, ethenedithione cannot, as had been proposed, be considered as the first example for the violation of Hund's rule in an equilibrium structure.