Low‐Dimensional Structural Units in Amine‐Templated Uranyl Oxoselenates(VI): Synthesis and Crystal Structures of [C₃H₁₂N₂][(UO₂)(SeO₄)₂(H₂O)₂](H₂O), [C₅H₁₆N₂]₂[(UO₂)(SeO₄)₂(H₂O)](NO₃)₂, [C₄H₁₂N][(UO₂)(SeO₄)(NO₃)], and [C₄H₁₄N₂][(UO₂)(SeO₄)₂(H₂O)]

Abstract

Abstract The crystals of four amine‐templated uranyl oxoselenates(VI), [C 3 H 12 N 2 ][(UO 2 )(SeO 4 ) 2 (H 2 O) 2 ](H 2 O) ( 1 ), [C 5 H 16 N 2 ] 2 [(UO 2 )(SeO 4 ) 2 (H 2 O)](NO 3 ) 2 ( 2 ), [C 4 H 12 N][(UO 2 )(SeO 4 )(NO 3 )] ( 3 ), and [C 4 H 14 N 2 ][(UO 2 )(SeO 4 ) 2 (H 2 O)] ( 4 ) were prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amine. The crystal structures of all four compounds have been solved by direct methods from X‐ray diffraction data. The structure of 1 (triclinic, ${\rm P}{\bar 1}$ , a = 7.5611(16), b = 7.7650(17), c = 12.925(3) Å, α = 94.605(18), β = 94.405(17), γ = 96.470(17)°, V = 748.8(3) Å 3 , R 1 = 0.029 for 2769 unique observed reflections) is based upon 0D‐units of the composition [(UO 2 ) 2 (SeO 4 ) 4 (H 2 O) 4 ] 4− . These discrete units are composed from two pentagonal [UO 7 ] 8− bipyramids linked via [SeO 4 ] 2− tetrahedra and are unknown in structural chemistry of uranium so far. The structure of 2 (monoclinic, C 2/ c , a = 28.916(5), b = 8.0836(10), c = 11.9856(16) Å, β = 110.909(11)°, V = 2617.1(6) Å 3 , R 1 = 0.035 for 2578 unique observed reflections) contains [(UO 2 )(SeO 4 ) 2 (H 2 O)] 2− chains of corner‐sharing pentagonal [UO 7 ] 8− bipyramids and [SeO 4 ] 2− tetrahedra. The chains run parallel to the c axis and are arranged into layers parallel to (100). In the structure of 3 (monoclinic, C 2/ m , a = 21.244(5), b = 7.1092(11), c = 8.6581(18) Å, β = 97.693(17)°, V = 1295.8(4) Å 3 , R 1 = 0.027 for 1386 unique observed reflections), pentagonal [UO 7 ] 8− bipyramids share corners with three [SeO 4 ] 2− tetrahedra each and an edge with a [NO 3 ] − anion to form [(UO 2 )(SeO 4 )(NO 3 )] − chains parallel to the b axis. In the structure of 4 (triclinic, ${\rm P}{\bar 1}$ , a = 6.853(2), b = 10.537(3), c = 10.574(3) Å, α = 99.62(3), β = 94.45(3), γ = 100.52(3)°, V = 735.6(4) Å 3 , R 1 = 0.045 for 2713 unique observed reflections), one symmetrically independent pentagonal [UO 7 ] 8− bipyramid shares corners with four [SeO 4 ] 2− tetrahedra to form the [(UO 2 )(SeO 4 ) 2 (H 2 O)] 2− chains parallel to the a axis. A comparison to related uranyl compounds is given.