Trithioarsenite

Trithioarsenite, also called sulfarsenite, is the trianion AsS3−3. It is a pyramidal anion, as is typical of other As^IIIX₃ compounds. It is generated by treatment of As₂S₃ with a sulfide:

As₂S₃ + 3 S²⁻ → 2 AsS3−3

A fundamental synthetic trithioarsenite is Na₃As₃, which features the pyramidal AsS3−3.^[1]

Thioarsenites are components of many sulfosalt minerals. An example is relatively common mineral proustite, Ag₃AsS₃,^[2][3][4] which is silver(I) trithioarsenite.