Carbon subsulfide

C₃S₂ was discovered by Béla Lengyel,[1] who assigned it an unsymmetrical structure. Later, infrared and Raman spectroscopy showed that the structure is symmetrical with a D_∞h point group symmetry,[2] i.e. S=C=C=C=S. This compound is analogous to carbon suboxide whose structure is O=C=C=C=O.

Lengyel first synthesized this compound by passing carbon disulfide (CS₂) vapor through an electric arc with carbon electrodes. This treatment produced a black solution that after filtration and evaporation gave a cherry-red liquid. He determined the molecular mass by cryoscopy. Later preparations of C₃S₂ include thermolysis of a stream of CS₂ in a quartz tube heated to 900 to 1100 °C as well as flash vacuum pyrolysis (FVP) of 1,2-dithiole-3-thiones.[3]

Among its few known reactions, C₃S₂ reacts with bromine to form the cyclic disulfide.[4]

C₃S₂ polymerizes under applied pressure to give a black semi-conducting solid. A similar pressure-induced polymerization of CS₂ also gives a black semiconducting polymer.

In addition, reactions of C₃S₂ can yield highly condensed sulfur-containing compounds, e.g. the reaction of C₃S₂ with 2-aminopyridine.

Using microwave spectroscopy, small C_nS₂ clusters have been detected in interstellar medium.[5] The rotational transitions of these molecular carbon sulfides matched with the corresponding molecules.