What are sulfanes and metal polysulfides?

Sulfanes and metal polysulfides are compounds that exhibit catenation, a property where atoms of the same element bond to one another to form chains or rings. In the oxygen group, sulfur is particularly noted for this ability, second only to carbon.1

Sulfanes

Sulfanes are compounds with the general formula ${\text{H}}_2{\text{S}}_x$, where $x$ typically represents a value of 2, 3, 4, or more. These molecules consist of zigzag chains of sulfur atoms bonded to hydrogen atoms at the ends.1

Metal Polysulfides

Metal polysulfides are compounds with the general formula ${\text{M}}_2{\text{S}}_x$, where M represents a singly charged metal ion and $x$ is 2, 3, 4, or more. These compounds are formed when water-soluble metal sulfides are heated in an aqueous solution with elemental sulfur, resulting in solutions containing polysulfide anions such as ${\text{S}}_3^{2-}$ and ${\text{S}}_4^{2-}$. Metal polysulfides are significant in the development of high-density power sources, including certain lithium and sodium sulfide batteries.12