Abstract
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 K2ReF6 starting material with KReO4. It consists of octa-hedral [Co(NH3)6]3+ cation (Co1 site symmetry 1), tetra-hedral [ReVIIO4]- anions (Re site symmetry 1) and octa-hedral [ReIVF6]2- anions (Re site symmetries 1and ). The [ReF6]2- octa-hedral anions (mean Re-F = 1.834 Å), [Co(NH3)6]3+ octa-hedral cations (mean Co-N = 1.962 Å), and the [ReO4]- 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.
Highlights
Chemical contextSalts of [ReF6]2À are typically prepared from the solid-state melting reaction of [ReX6]2À (X = Cl, Br, I) with AHF2 (A = NH4+, K+) followed by an aqueous work-up (Ruff & Kwasnik, 1934; Louis-Jean et al, 2018)
The molecular structure of (I) showing displacement ellipsoids drawn at the 50% probability level for all non-H atoms
All the Re—F bond lengths in the Re3- and Re4-centred anions are of equal distances of 1.952 (6) and 1.950 (6) A, respectively, by symmetry
Summary
Salts of [ReF6]2À are typically prepared from the solid-state melting reaction of [ReX6]2À (X = Cl, Br, I) with AHF2 (A = NH4+, K+) followed by an aqueous work-up (Ruff & Kwasnik, 1934; Louis-Jean et al, 2018). Such a procedure is found to be challenging. An improved procedure for the preparation of A2[ReF6] (A = K, Rb, Cs) salts as well as their X-ray single-crystal structures was recently reported The crystals of (I) are air stable over short periods, but decompose to a black material after six months of storage at ambient temperature
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