An unexpected rhenium(IV)-rhenium(VII) salt: [Co(NH 3 ) 6 ] 3 [Re VII O 4 ][Re IV F 6 ] 4 ·6H 2 O

The title hydrated salt, tris-[hexa-amminecobalt(III)] tetraoxidorhenate(VII) tetra-kis-[hexa-fluorido-rhenate(IV)] hexa-hydrate, arose unexpectedly due to possible contamination of the K ReF starting material with KReO . It consists of octa-hedral [Co(NH ) ] cation (Co1 site symmetry 1), tetra-hedral [Re O ] anions (Re site symmetry 1) and octa-hedral [Re F ] anions (Re site symmetries 1and ). The [ReF ] octa-hedral anions (mean Re-F = 1.834 Å), [Co(NH ) ] octa-hedral cations (mean Co-N = 1.962 Å), and the [ReO ] tetra-hedral anion (mean Re-O = 1.719 Å) are slightly distorted. A network of N-H⋯F hydrogen bonds consolidates the structure. The crystal studied was refined as a two-component twin.