Syntheses, Raman spectroscopy and crystal structures of alkali hexafluoridorhenates(IV) revisited

Abstract

The A 2[ReF6] (A = K, Rb, Cs) salts are isotypic and crystallize in the K2[GeF6] structure type.

Uncovering Multiple Metal–Metal Bonding in a Tetranuclear Fluoride Rhenium Cluster or the Curious Case of {[Ni(H2O)6](NH4)4}[Re4F18]·4H2O

“…In those reactions, the precursors, A 2 [ReX 6 ] (A = K, NH 4 ; X = Cl, Br) and ( n Bu 4 ) 2 [Re 2 Cl 8 ], were treated with molten bifluorides and the resulting A 2 [ReF 6 ] and (NH 4 ) 2 [Re 2 F 8 ] · 2H 2 O salts were obtained after washing with water/methanol mixtures. Recently, we also revisited the preparation and the crystallographic structure of A 2 [ReF 6 ](A = K, Cs, Rb) . Currently, the only reported [ReF 6 ] 2– salt containing a bulky organic cation (i.e., (PPh 4 ) 2 [ReF 6 ] · 2H 2 O) was prepared from (NH 4 ) 2 [ReF 6 ] in water.…”

An unexpected rhenium(IV)–rhenium(VII) salt: [Co(NH3)6]3[ReVIIO4][ReIVF6]4·6H2O

“…The chemistry of Re VII is dominated by the tetrahedral perrhenate anion, [ReO 4 ] À (Latimer, 1952;Abram, 2003) while Re IV is typically found in salts containing octahedral [ReX 6 ] 2À (X = F, Cl, Br, I) anions (Berthold & Jakobson, 1964;Jorgensen & Schwochau, 1965;Grundy & Brown, 1970;Louis-Jean et al, 2018). The salts of [ReX 6 ] 2À (X = Cl, Br, I) can be prepared in high yield by the reduction of a perrhenate starting material in the corresponding concentrated HX acid (Briscoe et al, 1931;Watt et al, 1963).…”

“…The salts of [ReX 6 ] 2À (X = Cl, Br, I) can be prepared in high yield by the reduction of a perrhenate starting material in the corresponding concentrated HX acid (Briscoe et al, 1931;Watt et al, 1963). However, salts of [ReF 6 ] 2À are typically prepared from the solid-state melting reaction of [ReX 6 ] 2À (X = Cl, Br, I) with AHF 2 (A = NH 4 + , K + ) followed by an aqueous work-up (Ruff & Kwasnik, 1934;Louis-Jean et al, 2018). Such a procedure is found to be challenging.…”

X-ray absorption fine structure spectroscopic study of (NH4)2ReF6

“…In compounds containing ReF 6 octahedra, the Re atom can be found in oxidation state +7 (e.g., ReF 6 (Sb 2 F l1 )) [1], +6 (e.g., ReF 6 ) [2], +5 (e.g., CsReF 6 ) [3], and +4 (e.g., A 2 ReF 6 ; A = K, Rb, Cs) [4]. Among these species, ReF 6 and ReF 6 2− have been the most studied.…”

“…Because technetium is a major fission product of the nuclear industry and rhenium is an often used as a homologue of technetium for studies related to nuclear cycle application, x-ray absorption study on rhenium halides could inform about the behavior of technetium halides in molten salts for nuclear fuel cycle reprocessing [12]. Among the ReF 6 2− salts, (NH 4 ) 2 ReF 6 has been used as a precursor for the preparation of compounds with interesting magnetic properties (e.g., [Zn(viz) 4 (ReF 6 )]; viz = vinylimidazole) [13]. While (NH 4 ) 2 ReF 6 has been characterized by powder x-ray diffraction [14], its single crystal structure has not been determined, and the Re-F distances in (NH 4 ) 2 ReF 6 are not reported.…”