Crystal chemistry of selenates with mineral-like structures: VIII. Butlerite chains in the structure of K(UO2)(SeO4)(OH)(H2O)

Abstract

A new potassium uranyl selenate compound K(UO 2 )(SeO 4 )(OH)(H 2 O) has been synthesized for the first time using the technique of evaporation from water solution. Its crystal structure has been solved by direct methods (monoclinic, P 2 1 / c , a = 8.0413(9) Å, b = 8.0362(9) Å, c = 11.6032(14) Å, β = 106.925(2) ° , V = 717.34 (14) Å 3 ) and refined to R 1 = 0.0319 ( wR 2 = 0.0824) for 1285 reflections with | F 0 | > 4 σ F . The structure consists of [(UO 2 (SeO 4 )(OH)(H 2 O)] -chains extending along axis b . In the chains, the uranyl pentagonal bipyramids are linked via bridged hydroxyl anions and tetrahedral oxoanions [SeO 4 ] 2-. Potassium ions are situated between these chains. No chains of that type have been observed in uranyl compounds earlier, but they had been detected in the structures of butlerite, parabutlerite, uklonskovite, fibroferrite, and a number of synthetic compounds.

Chemically Induced Polytypic Phase Transitions in the Mg[(UO2)(TO4)2(H2O)](H2O)4 (T = S, Se) System

“…There are more than 400 uranyl sulfates and selenates known nowadays (see refs − for recent reviews). One of the interesting problems is the absence of exact correspondence between sulfate and selenate systems, despite the structural and chemical similarity of Se 6+ and S 6+ ions.…”

Mixed Uranyl Sulfate–Selenates: Evolution of Structural Topology and Complexity vs Chemical Composition

“…2,5 It is noteworthy that there are several isotypic uranyl sulfates and selenates known, 6,7 which points out the possibility of Se 6+ −S 6+ substitution in minerals and synthetic compounds. For instance, adolfpateraite, K(UO 2 )(SO 4 )(OH)(H 2 O), 8 has both sulfate 9 and selenate 10 synthetic analogues. The study of the phase formation in mixed uranyl sulfate−selenate systems seems to be a promising avenue from both geochemical (mineralogical) and chemical points of view.…”

“…For instance, uranyl sulfate minerals do not contain any noticeable amounts of Se, and whereas uranyl sulfates are one of the most widespread natural secondary phases, uranyl selenates are unknown as minerals, though there are seven natural uranyl selenites reported to date. , It is noteworthy that there are several isotypic uranyl sulfates and selenates known, , which points out the possibility of Se 6+ –S 6+ substitution in minerals and synthetic compounds. For instance, adolfpateraite, K­(UO 2 )­(SO 4 )­(OH)­(H 2 O), has both sulfate and selenate synthetic analogues. The study of the phase formation in mixed uranyl sulfate–selenate systems seems to be a promising avenue from both geochemical (mineralogical) and chemical points of view.…”

“…compound Se content in structure S.G. a, Å/α, °b, Å/β, °c, Å/γ, °V, Å 3 R 1 (|Fo| ≥ 4σF) ICSD 100 P2 1 /c 11.456(2) 10.231(1)/101.901(4) 14 1 /c 11.4176(12) 10.2339(10)/101.796(2) 14.7868(15) 1691.3(3) 0.0224 430718 81.7 P2 1 /c 11.4014(3) 10.2270(3)/101.710(1) 14.7706(4) 1686.44(8) 0.0293 430717 78.5 C2/c 17.7579(18) 8.1510(7)/97.035(3) 17.7750(17) 2553.5(4) 0.0318 430725 76.8 C2/c 17.774(4) 8.1557(18)/97.089(4) 17.785(4) 2558.5(10) 0.0204 430722 80.5 C2/c 17.7681(16) 8.1487(7)/96.984(2) 17.7917(15) 2556.9(4) 0.0236 430726 76.8 C2/c 17.7245(4) 8.1359(2)/97.001(1) 17.7502(4) 2540.58(10) …”

A commensurately modulated structure of parabutlerite, FeIIISO4(OH)·2H2O

“…Chains of the same topology were also found in the structure of fibroferrite, [Fe III (OH)(H 2 O) 2 (SO 4 )](H 2 O) 3 (Scordari, 1981); and in numerous inorganic structures as well, among them, e.g. K(UO 2 )(SeO 4 )(OH)(H 2 O) (Gurzhii et al, 2010).…”