Synthesis and Structure of a Stable Bis(methylene)-λ4 -sulfane.

Bis(methylene)-λ4 -sulfane 1, a >C=S=C< heterocumulene, was obtained as a red crystalline solid from the reaction between elemental sulfur and a carbenoid that contains sterically demanding silylalkyl groups. Under atmospheric conditions, and even at elevated temperatures, 1 exhibits extraordinary stability. The molecular structure and electron-density distribution of 1 were analyzed by single-crystal X-ray diffraction analysis, which revealed a bent C=S=C geometry with C=S=C π-bonds. These results, combined with those of variable-temperature NMR measurements and theoretical calculations suggest a slow rotation of the S=C moieties in 1, the stability and structure of which were further examined by theoretical calculations.