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103Rh NMR chemical shiftshave been computed at theGIAO-B3LYP level of density functional theory (DFT) for a number of[Rh(COD)(P∩P)]+complexes [COD = 1,5-cyclooctadiene,P∩P = chelating bis(phosphine) including bis(dimethylphosphino)ethane(dmpe), bis(diphenylphosphino)ethane (dmpe), MeDUPHOS, DIOP, BINAP,and others]. Structures have been optimized using PBE0 and M06 functionalsin the gas phase, in a continuum modeling the solvent, and with [PF6]−counteranion included explicitly. Observedtrends in δ(103Rh) are well reproduced for pristinePBE0-optimized cations in the gas phase or for ion pairs optimizedin a continuum with M06. While there is no overall trend between computedδ(103Rh) values and complex stabilities (evaluatedthrough isodesmic ligand exchange reactions), there is a linear relationshipbetween the 103Rh chemical shifts and the mean Rh–Pbond distances. This relationship appears to be remarkably general,encompassing various chelating ring sizes and substituents at P, includingremote electron-donating and -withdrawing substituents that are characterizedthrough their Hammett constants. The combination of 103Rh NMR and DFT computations emerges as a useful tool for structureelucidation of Rh–phosphine complexes. [ABSTRACT FROM AUTHOR]

The reaction at 20 °C of the metallocenelanthanide hydride, [1,2,4-(Me3C)3C5H2]2CeH, UGRAPHIC DISPLAY="INLINE" ID="UGT1" SRC="UGT1"/, and excess methyltrifluoromethanesulfonate, CH3OSO2CF3, results in formation of UGRAPHIC DISPLAY="INLINE" ID="UGT2" SRC="UGT2"/, UGRAPHIC DISPLAY="INLINE" ID="UGT3" SRC="UGT3"/, UGRAPHIC DISPLAY="INLINE" ID="UGT4" SRC="UGT4"/ and the bimetallic complex UGRAPHIC DISPLAY="INLINE" ID="UGT5" SRC="UGT5"/. The metallocenes UGRAPHIC DISPLAY="INLINE" ID="UGT6" SRC="UGT6"/, UGRAPHIC DISPLAY="INLINE" ID="UGT7" SRC="UGT7"/, and UGRAPHIC DISPLAY="INLINE" ID="UGT8" SRC="UGT8"/ react with excess CH3OSO2CF3 to form UGRAPHIC DISPLAY="INLINE" ID="UGT9" SRC="UGT9"/, CH3OCH3, CH3F, and (CH3O)2SO, respectively, at 20 °C. Thus, the net reaction is UGRAPHIC DISPLAY="INLINE" ID="UGT10" SRC="UGT10"/ but the pathway is not a direct methyl transfer. Comparison of the reactivity of CH3OSO2CF3 and CH3OSO2CH3 (Werkema et al., Organometallics, 2012, 31, 870) is revealing since both form a similar set of products but the rates of reaction of CH3OSO2CF3 are faster. The bimetallic complex, in which the SO32− anion bridges two UGRAPHIC DISPLAY="INLINE" ID="UGT11" SRC="UGT11"/ fragments, is unique in organometallic chemistry. The 1H NMR spectrum is fluxional at 20 °C and the low temperature spectrum is consistent with the geometry observed in the solid state. Density Functional Theory (DFT) calculations of the Gibbs energy profiles for the reaction of CH3OSO2CF3 with UGRAPHIC DISPLAY="INLINE" ID="UGT12" SRC="UGT12"/ show that the CH-bond activation and direct CH3 group transfer have similar activation energy barriers. This contrasts with what is observed in the reaction of UGRAPHIC DISPLAY="INLINE" ID="UGT13" SRC="UGT13"/ with CH3OSO2CH3, where CH-bond activation at the SCH3 group is preferred. Remarkably, the activation energy barriers for C–O-bond cleavage are similar in CH3OSO2CH3 and CH3OSO2CF3, which is traced to the calculated small exoergicity of −1.7 kcal mol−1 for the reaction of UGRAPHIC DISPLAY="INLINE" ID="UGT14" SRC="UGT14"/. This contrasts, perhaps, with conventional wisdom that overemphasizes the effect of the electron-withdrawing ability of the CF3 group on the chemical and physical properties of sulfonate esters. [ABSTRACT FROM AUTHOR]

Reaction mechanisms for the oxidative reactions of CO2 and COS with [(C5Me5)2Sm] 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 [(C5Me5)2Sm-CO2-Sm(C5Me5)2] and [(C5Me5)2Sm-COS-Sm(C5Me5)2] as intermediates, respectively, ruling out radical coupling for the formation of the oxalate complex. [ABSTRACT FROM AUTHOR]

The experimental reaction of [1,2,4-(Me3C)3C5H2]2CeH, Cp′2CeH, and CH3OSO2CH3beginsby α-C–Hactivation of the SCH3group, forming Cp′2CeCH2SO2(OCH3), which evolves intoCp′2CeOCH3with elimination of CH2(and presumably SO2). Prolonged heating of thismixture (days at 60 °C) forms Cp′2CeOSO2CH3and CH3OCH3. The metallacycle[1,2,4-(Me3C)3C5H2][1,2-(Me3C)2-4-(Me2CCH2)C5H2]Ce, when presented with the choice of C–H bondsin CH3S and CH3O groups, deprotonates both withcomparable rates, ultimately forming Cp′2CeOCH3and Cp′2CeOSO2CH3at 20 °C. The experimental studies are illuminated by DFT calculationson the experimental systems, which show that the hydride selects themore acidic CH3S bond, whereas the metallacycle reactswith C–H bonds of both the CH3S and CH3O groups of CH3OSO2CH3. In the metallacyclereaction, the initially formed regioisomers, Cp′2CeCH2SO2(OCH3) and Cp′2CeCH2OSO2CH3, rearrange tothe observed products, Cp′2CeOCH3andCp′2CeOSO2CH3, respectively.Furthermore, C–H activation at the SCH3group formstwo isomers of Cp′2CeCH2SO2(OCH3) in the reaction of CH3OSO2CH3with the metallacycle and only one in the reactionwith the hydride. The lack of selectivity in the reactions of themetallacycle relative to the hydride is due to the metallacycle’sgreater thermodynamic advantage and lower energy barriers, which arelinked to the higher bond energy of Ce–H relative to Ce–Cin the metallacycle. [ABSTRACT FROM AUTHOR]

The determination of the solvation shell of Hg(ii)-containing molecules and especially the interaction between Hg(ii) and water molecules is the first requirement to understand the transmembrane passage of Hg into the cell. We report a systematic DFT study by stepwise solvation of HgCl2including up to 24 water molecules. In order to include pH and salinity effects, the solvation patterns of HgClOH, Hg(OH)2and HgCl3−were also studied using 24 water molecules. In all cases the hydrogen bond network is crucial to allow orbital-driven interactions between Hg(ii) and the water molecules. DFT Born–Oppenheimer molecular dynamics simulations starting from the stable HgCl2–(H2O)24structure revealed that an HgCl2–(H2O)3trigonal bipyramid effective solute appears and then the remaining 21 water molecules build a complete first solvation shell, in the form of a water-clathrate. In the HgCl2, HgClOH, Hg(OH)2–(H2O)24optimized structures Hg also directly interacts with 3 water molecules from an orbital point of view (three Hg–O donor–acceptor type bonds). All the other interactions are through hydrogen bonding. The cluster-derived solvation energies of HgCl2, HgClOH and Hg(OH)2are estimated to be −34.4, −40.1 and −47.2 kcal mol−1, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A predictive reactivity of Cp2An(IV)Me2 (with An=uranium [U], neptunium [Np] and plutonium [Pu]) with pyridine N-oxide has been studied at the theoretical level. The predictive reaction, which consists in the formation of a formaldehyde complex, begins after the initial formation of a cyclometalated complex produced by a C-H activation of the pyridine N-oxide. A difference of reactivity between U/Pu and Np has been observed and has been attributed to the presence of a more covalent bond between Np and the carbene group in the transition state of formation of a transient carbene intermediate. [ABSTRACT FROM AUTHOR]

Abstract: In the mid 1980s the study of ozone reactivity gained a significant interest with the discoveries of the stratospheric ozone hole () and of the ozone depletion events in the polar boundary layer (). In the stratosphere, the mechanism involves heterogeneous reactions on polar stratospheric clouds that lead to chlorine activation (). In contrast, tropospheric ozone depletion occurring during polar springtime rather involves reactive bromine species. They are released during a series of photochemical and heterogeneous reactions often called the bromine explosion (see the review of ). In this reaction sequence, an essential step is the generation of photolyzable Br2, the precursor of two Br atoms, via the multiphasic reaction (1): The production of reactive HOBr could occur with the oxidation of BrO by HO2. [Copyright &y& Elsevier]

The uranium(IV)/uranium(IV) μ-sulfide complex [{((AdArO)3N)U}2(μ-S)] reacts with CS2 to form the trithiocarbonate-bridged complex [{((AdArO)3N)U}2(μ-K2:K2-CS3)]. The trithiocarbonate complex can alternatively be formed in low yields from low-valent [((AdArO)3N)U(DME)] through the reductive cleavage of CS2. [ABSTRACT FROM AUTHOR]

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 carbon disulfide (CS2) with the side-on end-on dinitrogen complex ([NPNSi]Ta)2(μ-η1:η2-N2)(μ-H)2 (1) (where [NPNSi] = [PhP(CH2SiMe2NPh)2]) has been studied and shown to generate two products, the ratio of which depends on the concentration of added carbon disulfide. At high concentrations of CS2, N-N bond cleavage and functionalization occur to generate a ditantalum complex with an isothiocyanato ligand N-bound to Ta along with bridging sulfido and nitrido moieties. At lower concentrations of CS2, less dinitrogen functionalization is observed; instead, N2 is displaced and the CS2 molecule is completely disassembled to generate a ditantalum derivative with bridging methylene and two sulfide moieties. Kinetic and DFT studies have been performed and provide clues about the product ratio and mechanistic information and shed light on why N2 functionalization is challenging.

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.)

The synthesis and structural determination of the first thorium phosphinidene complex are reported. The reaction of 2 equiv of (C5Me5)2Th(CH3)2 with H2P(2,4,6-(i)Pr3C6H2) at 95 °C produces [(C5Me5)2Th]2(μ2-P[(2,6-CH2CHCH3)2-4-(i)PrC6H2] as well as 4 equiv of methane, 2 equiv from deprotonation of the phosphine and 2 equiv from C-H bond activation of one methyl group of each of the isopropyl groups at the 2- and 6-positions. Transition state calculations indicate that the steps in the mechanism are P-H, C-H, C-H, and then P-H bond activation to form the phosphinidene.

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.)

The uranium(IV)/uranium(IV) μ-sulfide complex [{(((Ad)ArO)(3)N)U}(2)(μ-S)] reacts with CS(2) to form the trithiocarbonate-bridged complex [{(((Ad)ArO)(3)N)U}(2)(μ-κ(2):κ(2)-CS(3))]. The trithiocarbonate complex can alternatively be formed in low yields from low-valent [(((Ad)ArO)(3)N)U(DME)] through the reductive cleavage of CS(2).