The Triple Salt 2(C 7 H 9 N 4 O 2 )[MoOCl 4 (H 2 O)] ⋅ 2(C 7 H 9 N 4 O 2 )Cl ⋅ (H 17 O 8 )Cl Containing a C 2 ‐symmetrical Unbranched H + (H 2 O) 8 Zundel type Species in a Framework Composed of Theophyllinium, Aquatetrachloridooxidomolybdate and Chloride Ions

From a concentrated hydrochloric acid solution of molybdenum‐(V) chloride and theophylline octaaquahydrogen(1+) tetrakis(theophyllinium) bis[aquatetrachloridooxidomolybdate(1−)] tri‐chloride, C 7 H 9 N 4 O 2 ) 4 (H 17 O 8 )[MoOCl 4 (H 2 O)] 2 Cl 3 , ( 1 ) was obtained. The light emerald green inorganic‐organic hybrid material can be rationalized as a triple salt according to the formula 2(C 7 H 9 N 4 O 2 )[MoOCl 4 (H 2 O)] ⋅ 2(C 7 H 9 N 4 O 2 )Cl ⋅ (H 17 O 8 )Cl. The ions involved are connected by charge‐supported hydrogen bonds to form a 3D framework. The unique H 17 O 8 + moiety features a chain of eight hydrogen bonded water molecules, with the excess proton defining a H 5 O 2 + Zundel ‐ion (O⋅⋅⋅O distance 240.3(6) pm) in the middle of the chain, and is placed with crystallographic site symmetry 2. Although engaged in strong O−H⋅⋅⋅O bonding to the neighboring water molecules in the chain (O⋅⋅⋅O distance 262.9(4) pm) and in hydrogen bonding to a carbonyl group of a theophyllinium ion, both the conformation of the H 5 O 2 + unit and the geometry of the very strong central O−H−O bond fit to the C 2 ‐symmetrical global minimum structure of an isolated H 5 O 2 + species. The outer water molecules of the H 17 O 8 + moiety are further engaged in N−H⋅⋅⋅O, O−H⋅⋅⋅Cl and O−H⋅⋅⋅O=C bonds.