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A joint experimental/theoretical (DFT) study of the activation of heteroallenes CO xS2- x ( x = 0-2) by [Sm(Giso)2] {Giso- = [(ArN)2CNCy2]-, Cy = cyclohexyl, Ar = 2,6-diisopropylphenyl} is reported. All heteroallenes are reduced in a different manner. Indeed, while activation of CS2 yields a bimetallic CS2 coupled product through C-S bond formation, CO2 forms an oxalate complex through C-C bond formation. This subsequently undergoes CO2 insertion into one of its Sm-N bonds. Finally, COS activation is predicted to yield a dithiocarbonate complex, through the formation of an intermediate sulfido complex [(Giso)2Sm(µ-S)Sm(Giso)2]. Therefore, [Sm(Giso)2] is a very versatile reagent, since it is a rare example of a complex that allows formation of several activation products involving valence isoelectronic substrates. This is rationalized by DFT calculations, and the latter emphasizes both the lack of kinetic stability of CS vs. CO and the high thermodynamic stability of the oxalate. [ABSTRACT FROM AUTHOR]

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 orthoC–H bond activation of several pyridine and pyridine N-oxide derivatives mediated by Cp2An(iv)(CH3)2and Cp2An(iii)(CH3) (Cp = C5H5and An = U, Np, Pu) have been investigated at the DFT level. For uranium(iv) complex, an excellent agreement with experimental observations is found, and particularly in the case of 2-picoline where only orthosp2C–H activation is observed without any sp3C–H activation. These differences of reactivity can be explained by the charges distribution at the metathesis transition state level. A predictive study of the reactivity of neptunium and plutonium complexes with pyridine and pyridine N-oxide is reported. This study shows that neptunium and plutonium have almost the same reactivity. The C–H activation mediated by actinide (iii) complexes have found to be more kinetically and thermodynamically favorable than for actinide (iv) complexes. The influence of 5f electrons on organoactinide reactivity is found to be small by comparing implicit and explicit treatment of 5f electrons. [ABSTRACT FROM AUTHOR]