Reductive silylation of a uranyl dibenzoylmethanate complex: an example of controlled uranyl oxo ligand cleavage

Abstract

Reaction of UO 2 (dbm) 2 (THF) (dbm ¼ OC(Ph)CHC(Ph)O) with 1 equiv. of R 3 SiH (R ¼ Ph, Et), in the presence of B(C 6 F 5) 3 , results in the formation of U(OB{C 6 F 5 } 3)(OSiR 3)(dbm) 2 (THF) (R ¼ Ph, 1; Et, 2), which were isolated as red-orange crystalline solids in good yields. Interestingly, the addition of 1 equiv. of H(dbm) to 2 results in protonation of the-OSiEt 3 ligand and formation of U(OB{C 6 F 5 } 3)(dbm) 3 (4) in 33% yield, along with formation of HOSiEt 3. Furthermore, addition of HOSiEt 3 and 1 equiv. of THF to 4, results in the formation 2, revealing that this process is reversible. The two-step conversion of UO 2 (dbm) 2 (THF) to 4 represents a rare example of controlled uranyl oxo ligand cleavage at ambient temperature and pressure. Comparison of diffraction and density functional theory data for 4 suggests the presence of the inverse trans influence, with a very shallow potential energy well for distortion along the trans U-O bond.

Synthesis, Characterization, and Stoichiometric U–O Bond Scission in Uranyl Species Supported by Pyridine(diimine) Ligand Radicals

“…Anal. Calcd for C 33 11.65 (29, 4H, m-ArH), 15.05 (14, 2H, 3,5-pyr−ArH), 20.31 (4, 1H, 4-pyr−ArH). IR: υ (SiCH3 symm bend) = 1246 cm −1 ; υ (SiCH3 asymm bend) = 840 cm −1 .…”

Uranium–Carbene–Imido Metalla‐Allenes: Ancillary‐Ligand‐Controlled cis‐/trans‐Isomerisation and Assessment of trans Influence in the R2C=UIV=NR′ Unit (R=Ph2PNSiMe3; R′=CPh3)

“…Clearly,s ignificant knowledge gaps are to be addressed:1 )A discrete R 2 C=U=NR unit remains a" missing piece"; 2) Very few heteroleptic combinations have been reported to date; and 3) Because in almosta ll cases uranium is in ah igh-oxidation state (V,V I), mid-valent (E=U IV =E') 0 + complexes are exceedingly rare, despite their clear importancea sp otentialm odelsf or two-electron-reducedu ranyl (O=U IV =O) 0 + ,w hich plays ak ey role in reductiveu ranylf unctionalisation and environmental mobility. [10] Herein, we report unprecedentedh eteroleptic mid-valent uranium(IV) cis-a nd trans-carbene-imido complexes, completing the uranium metalla-allene family.B oth the molecular structures and theoreticalc alculations show an electronic preference for the cis-geometry,w hich is attributed to a trans influence in mid-valent uranium systems,r ather than the ITI found in high-valent uranium analogues, in whicht he (E=U=E') n + units are overwhelmingly trans.T his work provides unambiguous experimental and theoretical support to the occurrence of the trans influence in actinide chemistry. [11] Lastly,w edemonstratet hat cis and trans isomers can be deliberately accessed, representing exceedingly rare examples of controllable cis/ trans isomerisation in f-blockc hemistry.…”

Facile Reductive Silylation of UO22+ to Uranium(IV) Chloride

“…[2] The persistence of these uranium(VI) species in nature is problematic due to their high water solubility and subsequent mobility;h owever, reduction to tetravalent species through pentavalent [UO 2 ] + intermediates in anaerobic conditions can mitigate this on account of the poor solubility of lower valent forms. [1] Though studied using avariety of methods, [2] including electrochemically [3] and photochemically, [4] af ruitful strategy for U = Or eduction is reductive silylation, where the driving force is formation of O À Si bonds.P revious reductive silylation systems are limited by the need for large excesses of silyl halides, [5][6][7] side reactivity of coordinated ligands [5,6] or their use as sacrificial reductants, [8] the need for pre-activation, [9][10][11] or the requirement of complex macrocyclic ligands. [12] Our progress in reductive silylation has suffered from similar flaws.W er ecently reported an ovel uranyl species,[ Cp*UO 2 ( Mes PDI Me )] (Cp* = 1,2,3,4,5-pentamethylcyclopentadienide, Mes PDI Me = 2,6-((Mes)N = CMe) 2 -C 5 H 3 N, Mes = 2,4,6-trimethylphenyl), bound by ar edox active pyridine(diimine) ligand.…”