Structure of uranyl complexes with acetylenedicarboxylic acid, K(H5O2)[UO2(OOCC≡CCOO)2 · H2O] · 2H2O and Cs2[UO2(OOCC≡CCOO)2 · H2O] · 2H2O

Uranyl complexes with acetylenedicarboxylic acid, K(H5O2)[UO2L2H2O] · 2H2O (I) and Cs2[UO2L2H2O] · 2H2O (II), L2− = C4O42− were prepared for the first time. The composition and structure of the complexes were determined by X-ray diffraction. The crystal data are as follows: a = 16.254(12) Å, b = 13.508(8) Å, c = 7.683(6) Å, β = 90.91(7)°, space group C2/c, V = 1687(2) Å3 (I); a = 7.0745(10), b = 18.4246(10), c = 13.1383(10) Å, space group Abm2, V = 1712.5(3) Å3 (II). The structures of I and II are based on [UO2L2H2O]n2− anionic chains stretched along the [101] direction (I) or [010] direction (II). In I and II, the uranium coordination polyhedron is a pentagonal bipyramid in which the equatorial environment of the uranyl ions is formed by the oxygen atoms of the four L2− anions and the water molecule. The L2− anions in I and II are bidentate bridging ligands connecting two uranium atoms that are next to each other in the anionic chain; their coordination capacity is equal to 2. In I, the K+ and H5O2+ cations are outer-sphere species. The latter form hydrogen bonds combining the anionic chains shifted by translation b with respect to each other. The [UO2L2H2O]n2− chains in I are surrounded by the potassium and oxonium cations; in II, these are combined by hydrogen bonds into anionic layers between which Cs+ cations are arranged. The IR spectrum of compound II was measured and interpreted.