Diaqua­iodidotetra­sarcosine­potassium: an overview of sarcosine metal halogenide structures

The monoclinic crystal structure of tetra­sarcosine potassium iodide dihydrate {or catena-poly[[potassium-tetra-μ-sarcosine-κ⁴O:O′;κ⁴O:O] iodide dihydrate]}, {[K(C₃H₇NO₂)₄]I·2H₂O}_n or Sar₄·KI·2H₂O (space group C2/c), comprises two crystallographically different sarcosine mol­ecules and one water mol­ecule on general positions, and one K⁺ cation and one I⁻ anion located on twofold axes. The irregular eight-coordinated K⁺ polyhedra are connected into infinite chains along [001] via sarcosine mol­ecules. This compound is the first sarcosine metal halogenide salt with a 4:1 ratio. A short overview of other sarcosine metal halogenide salts is presented and relationships to similar glycine salts are discussed.