Back Cover: Base‐Driven Assembly of Large Uranium Oxo/Hydroxo Clusters (Angew. Chem. Int. Ed. 25/2011)

Abstract

Low-valent uranium clusters provide good models to understand the formation and behavior of UO 2 nanoparticles. In their Communication on page 5745 ff., M. Mazzanti et al. present a reproducible method for the synthesis of such clusters. Benzoic acid is used to promote the formation of large oxo-hydroxo clusters, and cluster size can be tuned by the choice of solvent and base, thus leading to a U16 compound that is the largest U IV cluster reported to date.

One-dimensional chain structures of hexanuclear uranium(iv) clusters bridged by formate ligands

“…Single crystal X-ray diffraction reveals that the structures of 1a, 1b, and 2 each contain a typically hexanuclear core as observed in previously reported hexanuclear U(IV) clusters. [14][15][16][17][18][19][20]22 Within the hexanuclear core, six uranium atoms are arranged in a slightly distorted octahedral coordination geometry with U-U distances ranging from 3.790-3.875Å and they are bridged by eight m 3 -O sites which cap eight faces of the octahedron (Fig. 1a).…”

“…As reported in previous hexanuclear U(IV) clusters, those eight m 3 -O sites could be all O 2À groups, or all OH À groups, or half O 2À and half OH À groups. [14][15][16][17]19,20,22 Although it is difficult to locate the hydrogen atoms of these O sites and differentiate OH À from O 2À groups directly from electron density map due to the presence of heavy U atoms, those two groups can be distinguished by the U-O bond distance. According to literature, U(IV)-O distance are restricted to values between 2.21 and 2.27Å, whereas the U(IV)-OH distances are substantially longer and have a range from 2.41 to 2.48 A.…”

“…According to literature, U(IV)-O distance are restricted to values between 2.21 and 2.27Å, whereas the U(IV)-OH distances are substantially longer and have a range from 2.41 to 2.48 A. 16,17,19,20,22 In the structure of each compound, there are four O sites with U(IV)-O bond distances falling into the range of U(IV)-OH bond distance, where other four sites with U(IV)-O bond distances match that of U(IV)-O bond distances. The assignment of OH À and O 2À groups are also conrmed by bond valence calculations carried out for these O atoms using Brown's parameter (Table S1 † 460Å).…”

“…16 Biswas synthesized two large U(IV) clusters, decanuclear [U 10 O 8 (OH) 6 (bz) 14 4 with benzoic acid (bz) in acetonitrile solution. 17 24 ], from a solvothermal reaction of UCl 4 and benzoic acid in THF solvent. 18 These U(IV) clusters can be also synthesized in aqueous solution with the presence of N 2 H 4 as a reducing agent.…”

Solvothermal Synthesis of Tetravalent Uranium with Isophthalate or Pyromellitate Ligands

“…These led to the production of approximately twenty new structures that were isolated by using various organic ligands (formate, [13] acetate, [14][15][16] glycolate, [17] dipicolinate, [18][19][20] malonate, [21] fumarate, [22] benzoate, [23][24][25] terephthalate, [26,27] 4,4Ј-biphenyldicarboxylate, [26] 2,6-naphthalenedicarboxylate, [26] trimesate [28] ). The structural diversity of tetravalent uranium chemistry was also highlighted by the isolation of different nuclearities of inorganic building units, such as monomers, trimers, [28,[17][18][19][20][21] tetramers, [14][15][16]22] hexamers, [13,22,25,26] decamers, [24] hexadecamers, [24] chains [29] or, more recently, the U 38 poly-oxo cluster. [23] In the present contribution, we extended this systematic study to the use of two new carboxylate ligands, such as isophthalic acid (noted 1,3-H 2 bdc) or pyromellitic acid (or 1,2,4,5-benzentetracarboxylic, noted H 4 btec).…”