Diaquaiodidotetrasarcosinepotassium: an overview of sarcosine metal halogenide structures.

The monoclinic crystal structure of tetrasarcosine potassium iodide dihydrate {or catena-poly[[potassium-tetra-μ-sarcosine-κ(4)O:O';κ(4)O:O] iodide dihydrate]}, {[K(C(3)H(7)NO(2))(4)]I·2H(2)O}(n) or Sar(4)·KI·2H(2)O (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.