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A combined experimental and theoretical investigation on the cerium(IV) oxo complex [(L OEt ) 2 Ce(=O)(H 2 O)]⋅MeC(O)NH 2 (1; L OEt - =[Co(η 5 -C 5 H 5 ){P(O)(OEt) 2 } 3 ] - ) demonstrates that the intermediate spin-state nature of the ground state of the cerium complex is responsible for the versatility of its reactivity towards small molecules such as CO, CO 2 , SO 2 , and NO. CASSCF calculations together with magnetic susceptibility measurements indicate that the ground state of the cerium complex is of multiconfigurational character and comprised of 74 % of Ce IV and 26 % of Ce III . The latter is found to be responsible for its reductive addition behavior towards CO, SO 2 , and NO. This is the first report to date on the influence of the multiconfigurational ground state on the reactivity of a metal-oxo complex., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The first three insertion steps of propylene for isoselective metallocenes from the one-carbon-bridged cyclopentadienyl-fluorenyl {Cp/Flu} and silicon-bridged ansa-bis(indenyl) {SBI} families were computed by using a theoretical method implementing the B3PW91 functional in combination with solvent corrections incorporated with the Solvation Model based on Density (SMD) continuum model. For C 1 -symmetric {Cp/Flu}-type metallocenes, two mechanisms of stereocontrol were validated theoretically: more facile and more stereoselective chain "stationary" insertion (or site epimerization backskip) and less stereoselective alternating mechanisms. For the C 2 -symmetric {SBI}-type system, the computation results were in complete agreement with the sole operating chain migratory insertion mechanism. The thermochemical data obtained through the study were used to predict microstructures of polypropylenes by using three-parameter and one-parameter statistical models for the two metallocene systems, respectively. The calculated meso/rac pentad distributions were found to be in good agreement with those determined experimentally for isotactic polypropylene samples obtained at different polymerization temperatures., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The reaction of (C 5 Me 5 ) 2 Th(CH 3 ) 2 with the phosphonium salts [CH 3 PPh 3 ]X (X=Cl, Br, I) was investigated. When X=Br and I, two equivalents of methane are liberated to afford (C 5 Me 5 ) 2 Th[CHPPh 3 ]X, rare terminal phosphorano-stabilized carbenes with thorium. These complexes feature the shortest thorium-carbon bonds (≈2.30 Å) reported to date, and electronic structure calculations show some degree of multiple bonding. However, when X=Cl, only one equivalent of methane is lost with concomitant formation of benzene from an unstable phosphorus(V) intermediate, yielding (C 5 Me 5 ) 2 Th[κ 2 -(C,C')-(CH 2 )(CH 2 )PPh 2 ]Cl. Density functional theory (DFT) investigations of the reaction energy profiles for [CH 3 PPh 3 ]X, X=Cl and I showed that in the case of iodide, thermodynamics prevents the production of benzene and favors formation of the carbene., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Improving our comprehension of diverse CO 2 activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO 2 activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO 2 is readily reduced to CO, but isolated thorium(III) CO 2 activation is unprecedented. We show that the thorium(III) complex, [Th(Cp'') 3 ] (1, Cp''={C 5 H 3 (SiMe 3 ) 2 -1,3}), reacts with CO 2 to give the mixed oxalate-carboxylate thorium(IV) complex [{Th(Cp'') 2 [κ 2 -O 2 C{C 5 H 3 -3,3'-(SiMe 3 ) 2 }]} 2 (μ-κ 2 :κ 2 -C 2 O 4 )] (3). The concomitant formation of oxalate and carboxylate is unique for CO 2 activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO 2 activation can differ from better understood uranium(III) chemistry., (© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Reaction mechanisms for the oxidative reactions of CO(2) and COS with [(C(5)Me(5))(2)Sm] have been investigated by means of DFT methods. The experimental formation of oxalate and dithiocarbonate complexes is explained. Their formation involve the samarium(III) bimetallic complexes [(C(5)Me(5))(2)Sm-CO(2)-Sm(C(5)Me(5))(2)] and [(C(5)Me(5))(2)Sm-COS-Sm(C(5)Me(5))(2)] as intermediates, respectively, ruling out radical coupling for the formation of the oxalate complex., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)