Crystal Chemistry of Rubidium Uranyl Molybdates: Crystal Structures of Rb 6[(UO 2)(MoO 4) 4], Rb 6[(UO 2) 2O(MoO 4) 4], Rb 2[(UO 2)(MoO 4) 2], Rb 2[(UO 2) 2(MoO 4) 3] and Rb 2[(UO 2) 6(MoO 4) 7(H 2O) 2]

• Published in: Journal of solid state chemistry Vol. 168; no. 1; pp. 245 - 258
• Main Authors: Krivovichev, Sergey V., Burns, Peter C.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2002
• Subjects: crystal structure; rubidium uranyl molybdate; uranyl compounds; crystal structure; uranyl compounds; rubidium uranyl molybdate
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.2002.9717

Five Rb uranyl molybdates have been prepared by solid-state reactions and hydrothermal syntheses. The structure of each compound has been investigated using single-crystal X-ray diffraction data collected using Mo Kα radiation and a Charge-Coupled-device-based area detector. The structure of Rb 6[(UO 2)(MoO 4) 4] (monoclinic, C2/ c, Z=4, a=17.312(1) Å, b=11.5285(8) Å, c=13.916(1) Å, β=127.634(1)°, V=2199.4(3) Å 3, R 1=0.029) is based on finite clusters of composition [(UO 2)(MoO 4) 4] 6− composed of a UrO 4 ( Ur: UO 2 2+ uranyl ion) tetragonal bipyramid that shares each equatorial vertex with an adjacent MoO 4 tetrahedron. The structure of Rb 6[(UO 2) 2O(MoO 4) 4] (triclinic, P-1, Z=2, a=10.1567(5) Å, b=10.1816(5) Å, c=13.1129(6) Å, α=76.921(1)°, β=76.553(1)°, γ=65.243(1)°, V=1184.8(1) Å 3, R 1=0.047) is based upon chains of composition [(UO 2) 2O(MoO 4) 4] 6− containing UrO 5 pentagonal bipyramids and MoO 4 tetrahedra. The structure of Rb 2[(UO 2)(MoO 4) 2] (monoclinic, P2 1/ c, Z=8, a=12.302(1) Å, b=13.638(1) Å, c=13.508(1) Å, β=94.975(2)°, V=2257.8(4) Å 3, R 1=0.059) contains sheets of composition [(UO 2)(MoO 4) 2] 2− involving corner-sharing UrO 5 pentagonal bipyramids and MoO 4 tetrahedra. The structure of Rb 2[(UO 2) 2(MoO 4) 3] (orthorhombic, Pna2 1, Z=4, a=20.214(1) Å, b=8.3744(4) Å, c=9.7464(5) Å, V=1649.9(1) Å 3, R 1=0.027) consists of a framework with composition [(UO 2) 2(MoO 4) 3] 2− that involves corner-sharing UrO 5 pentagonal bipyramids and MoO 4 tetrahedra. The structure of Rb 2[(UO 2) 6 (MoO 4) 7 (H 2O) 2] (orthorhombic, Pbcm, Z=4, a=13.961(2) Å, b=10.7515(16) Å, c=25.579(4) Å, V=3839(1) Å 3, R 1=0.037) consists of a framework of corner-sharing UrO 5 pentagonal bipyramids, UrO 4(H 2O) pentagonal bipyramids and MoO 4 tetrahedra. These structures are compared to those of other uranyl molybdates. The structural diversity and variability of uranyl molybdates is related to the high degree of flexibility of the U–O–Mo linkages.