TY - JOUR
T1 - Polynuclear cation-cation complexes of pentavalent uranyl
T2 - Relating stability and magnetic properties to structure
AU - Nocton, Grégory
AU - Horeglad, Pawel
AU - Pécaut, Jacques
AU - Mazzanti, Marinella
PY - 2008/12/10
Y1 - 2008/12/10
N2 - Reaction of {[UO2Py5][μ-KI2Py 2]}n (1) with 2 equiv of potassium dibenzoylmethanate (Kdbm) in pyridine or acetonitrile affords, respectively, the corresponding tetranuclear complexes of pentavalent uranyl {[UO2(dbm) 2]2[μ-K(Py)2]2[μ8- K(Py)]}2I2·Py2 (2) (in 70% yield) and {[UO2(dbm)2]2[μ-K(MeCN)2] [μ8-K]}2 (3) (in 40% yield) in which four UO 2+ are mutually coordinated (T-shaped "cation- cation" interaction). The X-ray structures of 2 and 3 show also the presence of, respectively, six and four potassium cations involved in UO 2+⋯K+ interactions. Reaction of 2 with an excess of 18-crown-6 (18C6) affords the dimeric complex [UO 2(dbm)2K(18C6)]2 (4) presenting a diamond-shaped interaction between two UO2+ groups, in 45% yield. 1H and PFGSTE diffusion NMR spectroscopy of 2 and 3 in pyridine show unambiguously the presence of UO2+⋯ UO2+ and UO2+⋯K+ interactions (tetrametallic species) in solution, which leads to a rapid (7 days) disproportionation of pentavalent uranyl to afford [U(dbm)4] and [UO2(dbm)2] species. The UO2 +⋯K+ interaction plays an important synergistic role in the stabilization of the UO2+⋯UO 2+ interactions. Accordingly, the lower affinity of (K(18C6))+ for the uranyl(V) oxygen in complex 4 results in a lower number of coordinated K+ and therefore in a weakened UO 2+⋯UO2+ interaction. The UO2+⋯UO2+ interactions is completely disrupted in dmso or in the presence of Kdbm, preventing disproportionation of pentavalent uranyl. Solid-state variable-temperature magnetic susceptibility studies showed the unambiguous presence of antiferromagnetic coupling between the two oxo-bridged uranium centers of complex 4, with the appearance of a maximum in χ versus T at ∼5 K. The different behavior of the tetrameric complex 3, which probably involves a magnetic coupling occurring at lower temperature, can be ascribed to the different geometric arrangement of the interacting uranyl(V) groups.
AB - Reaction of {[UO2Py5][μ-KI2Py 2]}n (1) with 2 equiv of potassium dibenzoylmethanate (Kdbm) in pyridine or acetonitrile affords, respectively, the corresponding tetranuclear complexes of pentavalent uranyl {[UO2(dbm) 2]2[μ-K(Py)2]2[μ8- K(Py)]}2I2·Py2 (2) (in 70% yield) and {[UO2(dbm)2]2[μ-K(MeCN)2] [μ8-K]}2 (3) (in 40% yield) in which four UO 2+ are mutually coordinated (T-shaped "cation- cation" interaction). The X-ray structures of 2 and 3 show also the presence of, respectively, six and four potassium cations involved in UO 2+⋯K+ interactions. Reaction of 2 with an excess of 18-crown-6 (18C6) affords the dimeric complex [UO 2(dbm)2K(18C6)]2 (4) presenting a diamond-shaped interaction between two UO2+ groups, in 45% yield. 1H and PFGSTE diffusion NMR spectroscopy of 2 and 3 in pyridine show unambiguously the presence of UO2+⋯ UO2+ and UO2+⋯K+ interactions (tetrametallic species) in solution, which leads to a rapid (7 days) disproportionation of pentavalent uranyl to afford [U(dbm)4] and [UO2(dbm)2] species. The UO2 +⋯K+ interaction plays an important synergistic role in the stabilization of the UO2+⋯UO 2+ interactions. Accordingly, the lower affinity of (K(18C6))+ for the uranyl(V) oxygen in complex 4 results in a lower number of coordinated K+ and therefore in a weakened UO 2+⋯UO2+ interaction. The UO2+⋯UO2+ interactions is completely disrupted in dmso or in the presence of Kdbm, preventing disproportionation of pentavalent uranyl. Solid-state variable-temperature magnetic susceptibility studies showed the unambiguous presence of antiferromagnetic coupling between the two oxo-bridged uranium centers of complex 4, with the appearance of a maximum in χ versus T at ∼5 K. The different behavior of the tetrameric complex 3, which probably involves a magnetic coupling occurring at lower temperature, can be ascribed to the different geometric arrangement of the interacting uranyl(V) groups.
U2 - 10.1021/ja804766r
DO - 10.1021/ja804766r
M3 - Article
C2 - 19049459
AN - SCOPUS:57549095743
SN - 0002-7863
VL - 130
SP - 16633
EP - 16645
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 49
ER -