A Water Sensitive Hydrate: The Bis‐ Catena Complex Salt [Mn(H 2 O) 6 ][BiI 4 ] 2 ·2H 2 O

Bright red crystals of [Mn(H 2 O) 6 ][BiI 4 ] 2 · 2H 2 O are obtained from a solution of MnI 2 , BiI 3 , and I 2 in absolute ethanol, which is exposed to humid air. Reversible dehydratization sets in at about 50 °C. Added water decomposes the hydrate by irreversible precipitation of BiOI. The optical bandgap is about 1.9(1) eV. X‐ray diffraction on a single‐crystal revealed a monoclinic lattice (space group P 2 1 / c ) with a = 760.39(4) pm, b = 1315.6(1) pm, c = 1398.37(7) pm, and β = 97.438(4)°. In the crystal structure zigzag chains of edge‐sharing [BiI 2/1 I 4/2 ] – octahedra and linear strings of H 2 O‐bridged [Mn(H 2 O) 6 ] 2+ octahedra run parallel [100].