The Cation-Deficient Ruddlesden-Popper Oxysulfide Y2Ti2O5S2 as a Layered Sulfide: Topotactic Potassium Intercalation To Form KY2Ti2O5S2

Potassium intercalation into the cation-deficient n = 2 Ruddlesden-Popper oxysulfide Y2Ti2O5S2 to form KY2Ti2O5S2 has been carried out by reaction of the oxysulfide with potassium vapor in sealed metal tubes at 400 °C, potassium naphthalide in THF at 50 °C, or potassium in liquid ammonia at temperatures as low as -78 °C. Insertion of potassium is topotactic, and although a site 12-coordinate by oxide ions is vacant in the perovskite-...