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, C7H9N4O2)(4)(H17O8)[MoOCl4(H2O)](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(C7H9N4O2)[MoOCl4(H2O)] . 2(C7H9N4O2)Cl . (H17O8)Cl. The ions involved are connected by charge-supported hydrogen bonds to form a 3D framework. The unique H17O8+ moiety features a chain of eight hydrogen bonded water molecules, with the excess proton defining a H5O2+ 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 H5O2+ 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 H5O2+ species. The outer water molecules of the H17O8+ moiety are further engaged in N-H...O, O-H...Cl and O-H...O=C bonds.