The Mixed‐Valence C atena ‐Heteropolycation (Bi 2 S 2 ) +

The reaction of Bi and Bi 2 S 3 in the Lewis‐acidic ionic liquid [BMIm]Cl ⋅ 4.3AlCl 3 (BMIm=1‐ n ‐butyl‐3‐methylimidazolium) at 200 °C yielded air‐sensitive black crystals of (Bi 2 S 2 )[AlCl 4 ]. X‐ray diffraction on single‐crystals revealed a monoclinic structure containing infinite chains∞1 ( Bi 2 S 2) + . These polycations contain bismuth(II,III) and sulfur(‐II) atoms, connected by polar covalent Bi−S and Bi−Bi bonds. The assignment of bonds is ambiguous as a distinction between primary and secondary interactions is arbitrary based on interatomic distances. A real‐space quantum chemical bonding analysis, including delocalization indices, helped to quantify the interactions and charge distribution, confirming that a simple Lewis formula is inappropriate to describe the polycation.