Uranium Going the Soft Way: Low-Valent Uranium(III) Coordinated to an Arene-Anchored Tris-Thiophenolate Ligand

Abstract

The synthesis of a tripodal, S-based ligand, namely the mesitylene-anchored, tris-thiophenolate-functionalized (mes-( Me,Ad ArS) 3 ) 3− (1) 3− , and its coordination chemistry with lowvalent uranium to form [U III ((SAr Ad,Me ) 3 mes)] (1-U) are reported. Single-crystal X-ray diffraction analysis reveals a C 3 -symmetric molecular structure. Full characterization of 1-U was performed using nuclear magnetic resonance, UV−vis−NIR electronic absorption, and electron paramagnetic resonance spectroscopies as well as SQUID magnetometry, thus confirming the U(III) oxidation state. Alternating current magnetic studies show that 1-U exhibits single-molecule magnet behavior at low temperatures in a non-zero external field. Comparison of these results to those of the previously reported mesitylene-anchored complexes, [U III ((OAr Ad,Me ) 3 mes)] and [U III ((OAr tBu,tBu ) 3 mes)], indicates a drastic change in the electronic structure when moving from phenolate-based ligands to thiophenolate-based 1, which is further discussed by means of computational analysis (NBO, DFT, and QTAIM). Despite the U−O bonds being stronger, a much higher covalency was found for the U−S analogue. Article pubs.acs.org/IC

A Route to Stabilize Uranium(II) and Uranium(I) Synthons in Multimetallic Complexes

“…In comparison, the U III precursor 3 shows a similar well‐defined EPR spectrum (Figure S56) in frozen solution state (30 mM in 1 : 1 THF/Et 2 O) with g ‐values 2.71, 1.01 and 0.75 corresponding to a pseudo axial system. Similar g ‐values were reported for several U III complexes [21a–c, 12h, 21d] …”

Contrasting behaviour under pressure reveals the reasons for pyramidalization in tris(amido)uranium(III) and tris(arylthiolate) uranium(III) molecules

“…The U-S distances in US3 (range 2.7057(19)-2.7143(18) Å) are similar to those in Meyer's recently reported U III adduct of a chelating tris-thiophenolate (U-S distance = 2.7083(8) Å), both of which are much shorter than the few other U III -S compounds in the literature (range 2.77-2.87 Å) 19,[26][27][28] . The M-S-C ipso angles in US3 are more acute (78.7(2)-86.68(16)°) than all including the tris-thiophenolate (92.31(9)°) 27,28 . The short U-C contacts in US3 are benzylic-type interactions with the ipso and one ortho carbon in each ligand ring (Fig.…”

A Combined Experimental and Theoretical Investigation of Arene-Supported Actinide and Ytterbium Tetraphenolate Complexes

“…This δsymmetry is also observed in the SOMOs of structurally similar U(III) complexes of mesitylene-anchored tris(phenolate) or tris(thiophenolate) ligands. 37,38 The differences between the way the additional electron density resides on the metal or the arene upon reduction of 1An are best visualized with an unpaired spin density plot. These are shown in Figure 7a,b for [1Th] − and [1U] − , respectively.…”