Insight into the Reaction Mechanisms of (MeC₅H₄)₃U with Isoelectronic Heteroallenes CS₂, COS, PhN₃, and PhNCO by DFT Studies: A Unique Pathway that Involves Bimetallic Complexes

Abstract

The mechanisms of the reduction of four isoelectronic heteroallenes (CS(2), COS, PhN(3), and PhNCO) by trivalent uranium complex (MeC(5)H(4))(3)U were determined by using DFT methods. The experimental formation of either the bimetallic CS(2) and the PhNCO uranium(IV) adducts or the bimetallic sulfide complex (COS) and the monometallic uranium(V) phenylimide complex (PhN(3)) were rationalized. The formation of the products was explained by a unique reaction mechanism with a uranium(IV)-bridged heteroallene intermediate.

Controlling selectivity in the reductive activation of CO2 by mixed sandwich uranium(iii) complexes

“…Previous theoretical studies from our group have identified two possible reaction mechanisms for the formation of a dimeric bridging carbonate complex (Scheme 3). 39,40,41,42 The first step in both of them is the formation of a bimetallic complex with a doubly reduced to CO 2 2moiety bridging two oxidized U(IV) centers (the one-electron reduced monomeric species LU-OCO was considered , but is some 35 kcal mol -1 higher in energy than the dimer). This key intermediate has been determined as the starting point for both possible pathways leading to bimetallic carbonate complexes.…”

Activation of Heteroallenes COxS2–x (x = 0–2): Experimental and Theoretical Evidence of the Synthetic Versatility of a Bulky Guanidinato SmII Complex

“…This is in line with previous reports on CS 2 activation with either Sm II or U III complexes, where the low kinetic stability of the formed CS was already underlined. [29][30][31] In the same way, on the basis of previous work, [29] the formation of thiooxalate is predicted to involve a relatively high barrier preventing this reactivity. Finally, the C-S bond formation was investigated.…”

“…This yields the key intermediate, [(Giso) 2 Sm(μ-η-CS 2 )Sm(Giso) 2 ], which controls the subsequent reactivity. [29] The resultant formation of a sulfido complex, [(Giso) 2 Sm(μ-S)Sm(Giso) 2 ], is found to be endothermic (see Supporting Information) because of the lack of kinetic stability of the formed CS. This is in line with previous reports on CS 2 activation with either Sm II or U III complexes, where the low kinetic stability of the formed CS was already underlined.…”

Computational Comparative Mechanistic Study of C−E (E=C,N,O,S) Coupling Reactions through CO2 Activation Mediated by Uranium(III) Complexes

“…The study of these catalytic systems is therefore of fundamental importance to understand the role of 5 f orbitals in homogeneous catalysis, and contributes to the evaluation and rational design of new types of catalytic systems. Computational tools have been used to gain mechanistic insights into U III ‐mediated CO 2 activation …”

“…Computational tools have been used to gain mechanistic insights into U III -mediated CO 2 activation. [28,29,32,34,[42][43][44] In an earlier work, [32] we reported ad ensity functional study to understandt he mechanistic issueso ft he insertionr eactions of CO 2 and CS 2 into the UÀCb ond of a( Tp*) 2 UCH 2 Ph complex, stimulated by the work of Bart et al, [30] and proposedt hat the stronger electronegativity of the Oa tom compared with the S atom was responsiblef or the highera ctivity of CO 2 than CS 2 in their insertion and the subsequents ilylation. The question remaining to be addressed is as atisfactory descriptiono ft he silylation of the insertion product.…”