Reduction of CO₂ and CS₂ with Uranium(III) Metallocene Aryloxides

Abstract

The reactivity of two metallocene aryloxide U(III) complexes, [(C 5 Me 5 ) 2 U(O−Ar)], Ar = 4-t BuC 6 H 4 , 1; Ar = 2,6-t Bu 2 -4-CH 3 C 6 H 2 (BHT), 3, with CO 2 and CS 2 has been investigated. The reaction of 1 with CO 2 produces a bridging oxo complex, [{(C 5 Me 5 ) 2 (4-t BuC 6 H 4 −O)U} 2 (μ 2 -O)], 4, while 3 with CO 2 results in reductive disproportionation to form the bridging carbonate species, [{(C 5 Me 5 ) 2 (BHT)U} 2 (μ 2 -κ 2 :η 1 -CO 3 )], 5. The difference in reactivity can be attributed to the steric properties of the ligand because the reaction of 3 with an oxo-delivering agent yields a U(V) terminal oxo complex, [(C 5 Me 5 ) 2 (BHT)UO], 6. Reduction of CS 2 to form a bridging (CS 2 ) 2− ligand, [{(C 5 Me 5 ) 2 ( t BuC 6 H 4 −O)U} 2 (μ 2 -CS 2 )], 7, is observed with 1, while the reaction of 3 with CS 2 also produces a bridging (CS 2 ) 2− reduced ligand complex, followed by C−H bond activation of a methyl group from one (C 5 Me 5 ) 1− ring, [(C 5 Me 5 ) 2 (BHT)U{μ 2 -C(H)S 2 }U(C 5 Me 4 CH 2 )(C 5 Me 5 )(BHT)], 8. All compounds are characterized by NMR and IR spectroscopy, and their solid-state structures are determined by X-ray crystallography.

Isolation of C1 through C4 derivatives from CO using heteroleptic uranium(iii) metallocene aryloxide complexes

“…S3†) which shows similar features to 1 . 76 The optimized geometry compares well with the experimental one with a maximum deviation of 0.03 Å on the U–C CO distance. The CO bond appears to be slightly elongated 0.03 Å with respect to free CO.…”

Facile Oxidation of Ce(III) to Ce(IV) Using Cu(I) Salts

“…The coordination environment plays a pivotal role in stabilizing Ce­(IV) compounds, especially when oxidizing Ce­(III) to Ce­(IV) with a one-electron oxidant . With our recent interest in trivalent uranium reduction chemistry using the heteroleptic metallocene aryloxide ligand framework, [(C 5 Me 5 ) 2 (ArO)­U], Ar = 2,4,6-Me 3 C 6 H 2 (Mes), 4- t BuC 6 H 4 , and 2,6- t Bu 2 -4-MeC 6 H 2 , − we turned our attention to using a similar ligand framework, [(C 5 Me 5 ) 2 (2,6- i Pr 2 C 6 H 3 O)­Ce], to isolate organocerium­(IV) complexes, as well as investigate how this ligand set affects the electrochemical and photoluminescence properties of the Ce­(III) complex.…”

Cooperative dihydrogen activation with unsupported uranium–metal bonds and characterization of a terminal U(iv) hydride

“…Subsequently, we reported the uranium(III) complex heteroleptic ligand framework, [(C 5 Me 5 ) 2 (MesO)U(THF)], 1, Mes = 2,4,6-Me 3 C 6 H 2 , 66 and have been investigating the reactivity of this complex with small molecules. 67,68 We surmised the addition of [E(C 5 Me 5 )] n , E = Al, n = 4, Ga, n = 1, given their strong Lewis basicity, could produce a metal-metal bonded species by displacement of the THF solvent molecule and lead to an unsupported U-E bond, and the combination of these lowvalent fragments would lead to more enhanced reactivity.…”