Sn
19.3Cu
4.7As
22I
8, a new clathrate-I compound with a cationic host framework containing transition metals, has beensynthesized, and its crystal structure has been determined. It crystallizes in the cubic
space group
Pm
n with aunit cell parameter
a = 11.1736(3) Å and
Z = 1 (
R = 0.031 for 329 independent reflections and 22 variables).Tin, copper, and arsenic form the cationic clathrate framework hosting the guest iodine anions in cages of twodifferent shapes. Sn
19.3Cu
4.7As
22I
8 does not contain vacancies in the framework but reveals three partially occupiedpositions of the metal atoms, leading to the formation of Sn-Sn and Sn-Cu bonds that differ in length. The
119SnMössbauer spectrum confirms the local environment of tin atoms. The hyperfine constants obtained from theMössbauer spectra for different cationic tin clathrates are discussed. Electron diffraction and electron microscopyreveal that the splitting affects the short-range ordering but does not lead to a superstructure. Though containinga transition metal, Sn
19.3Cu
4.7As
22I
8 is diamagnetic, and its composition corresponds to the Zintl formalism.