Dinuclear uranium alkoxides. Preparation and structures of KU2(OCMe3)9, U2(OCMe3)9, and U2(OCHMe2)10, containing [uranium(IV), uranium(IV)], [uranium(IV), uranium(V)], and [uranium(V), uranium(V)], respectively

Cation‐Mediated Conversion of the State of Charge in Uranium Arene Inverted‐Sandwich Complexes

“…. A few mixed-valent diuranium complexes have been structurally characterized [56][57][58][59][60][61] with only one example of mixed valent inverted-sandwich complex. [23] Such species are attractive for the study of the possible presence of valence delocalization in uranium systems.…”

Oxo–Group‐14‐Element Bond Formation in Binuclear Uranium(V) Pacman Complexes

“…Similar U À O bond lengths are present in [U 2 A C H T U N G T R E N N U N G (OiPr) 10 ] (e.g., 2.03(1) ), the only other structurally characterised uranium(V) isopropoxide complex. [9,27] The opposing exo oxo group, O4, remains bound to a lithium cation resulting in a much shorter U2ÀO4 multiple bond of 1.865 (2) . As was indicated by the comparable 1 H NMR spectra, 5 is isostructural with the mixed lithium/silyl complex 3, with the complexes displaying similar bonding between the uranium(V) centres and their endo bridging oxygen ligands.…”

Isolation of a Star‐Shaped Uranium(V/VI) Cluster from the Anaerobic Photochemical Reduction of Uranyl(VI)

“…Both products were characterized by X-ray diffraction studies.T he X-ray crystal structure of the polymeric {[UO 2 -(PhCOO) 3 ][K(Py) 2 ]} n (see the SI) shows the presence of uranyl(VI) cations eight-coordinate,w ith ah exagonal bipyramidal geometry,b yt wo trans oxo groups and six oxygen atoms from three bidentate benzoate ligands.Apotassium cation, bound to two pyridine molecules and four oxygen atoms of the benzoate ligands from two different [UO 2 -(PhCOO) 3 ] À units,b ridges the uranyl(VI) complexes to afford ap olymeric structure.T he uranyl(VI) moieties have the typical linear geometry (179(1)8 8)a nd the U=Ob ond lengths (mean value 1.773 (7) )a nd the UÀO carboxylate bond distances (ranging from 2.429(4) to 2.525(4) )a re in the range of other structurally characterized uranyl(VI) carboxylate complexes. [14] Thes olid state structure of 5 consists of ad iscrete hexadecanuclear uranium oxo cluster with aU 16 O 24 core (Figure 2) 16 O 24 (PhCOO) 24 (Py) 2 ]} may due to af luxional behavior of the benzoate ligands.T he signals assigned to complex 1 were not observed. This indicates that rapid disproportionation of uranyl(V) occurs in the presence of two equivalents of potassium benzoate but does not lead to complex 1.T he previously reported disproportionation of uranyl(V) in the presence of benzoic acid did not afford 1 either but auranium-(IV) cluster [U 6 O 4 (OH) 4 (PhCOO) 12 (Py) 3 ], and the uranyl-(VI) complex [UO 2 (PhCOO) 2 (Py) 2 ].…”

“…[14] Themean U yl À(m 3 -O) distance is 2.33 (4) while the mean U1 À (m 3 -O) distance is 2.17 (4) .T he mean U1 À (m 3 -O) distance is slightly longer than the U V À (m-O) bond distances found in dinuclear uranium(V) bis-m-oxo complexes (2.094(12)-2.12 (13) ) [15] probably due to the triply bridging coordination mode of the oxo group.T his distance remains shorter than bridging UÀOd istances found in dinuclear uranium(V) alkoxide complex (2.29 (1) ). [16] U À Od istances ranging from 2.1 to 2.4 are reported for the pentagonal bipyramidal non-uranyl U V cation found in the mineral wyartite of formula CaU V (U VI O 2 ) 2 (CO 3 )O 4 (OH)(H 2 O) 7 . [17] TheX -band (9.40 GHz) EPR spectrum of 1 shows an intense signal at 10 Kw ith fitted g-values of 1.78, 1.46, 0.44 confirming the presence of uranium in the oxidation state + +V.…”

“…Here we showthat the photolysis of partially hydrated uranyl(VI) in anaerobic conditions leads to the reduction of uranyl(VI), and to the incorporation of the resulting U V species into the stable mixedvalent star-shaped U VI /U V oxo cluster [U(UO 2 ) 5 (m 3 -O) 5 -(PhCOO) 5 (Py) 7 ]( 1). This cluster is only the second example of aU VI /U V cluster and the first one associating uranyl groups to anon-uranyl(V) center.The U V center in 1 is stable,while the reaction of uranyl(V) iodide with potassium benzoate leads to immediate disproportionation and formation of the U 12 IV U 4 V O 24 cluster {[K(Py) 2 ] 2 [K(Py)] 2 [U 16 O 24 (PhCOO) 24 -(Py) 2 ]} (5).…”