On the proton‐acceptor properties of [TeMo 6 O 24 ] 6− in Na 4 (NH 4 ) 2 [TeMo 6 O 24 ] · 16H 2 O

Colourless triclinic single crystals of Na 4 (NH 4 ) 2 [TeMo 6 O 24 ] · 16H 2 O were grown in aqueous solution (space group P 1 , a = 1 075.3(1), b = 1 074.2(1), c = 1 089.8(1) pm, = 96.259(9), β = 118.556(7), γ = 113.355(8)°, Z = 1, 295 K, 311 parameters, 3 689 reflections, R g = 0.0197). There are two crystallographically independent Na + cations. Na(1) is coordinated octahedrally by four water molecules and two oxygen atoms of the centrosymmetric [TeMo 6 O 24 ] 6− anion. Na(2) is bound to five water molecules in a considerably distorted trigonally bipyramidal fashion. These bipyramids are linked with NH 4 + by hydrogen bonds to yield centrosymmetric cluster cations consisting of two NH 4 + and two Na(H 2 O) 5 + each. Hydrogen bonds envolving all except one (O(10)) of the oxygen atoms of the [TeMo 6 O 24 ] 6− anion as almost equivalent proton acceptors regardless of their bonding mode to Te and Mo, respectively, establish further connections to NH 4 + and the water of crystallization.