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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-iPr3C6H2) at 95 °C produces [(C5Me5)2Th] 2 (μ2-P[(2,6-CH2CHCH3)2-4-iPrC6H2] 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. [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 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 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]

Density functional theory calculations have been performed to calculate the one-electron redox potential for a series of oxoiron(IV) porphyrin complexes of the form [(TMP)Fe(IV)(O)(L)] (TMP = 5,10,15,20-tetramesitylporphyrinate). Different axial ligands were chosen (L = none, Im, ClO4(-), CH3CO2(-), Cl(-), F(-), SCH3(-)) in order to compare the results with recent electrochemical experiments. The redox potentials were calculated with a Born-Haber cycle and the use of an internal reference, i.e. the absolute redox potential of ferrocene. Diverse methodologies were tested and show that the computed redox potentials depend strongly on the functional, the basis set, and the continuum models used to compute the solvation energies. Globally, BP86 gives better results for the geometries of the complexes than B3LYP and M06-L as well as more consistent values for the redox potentials. Although the results fit the experimental data for L = Im and L = ClO4(-), the addition of the other anionic axial ligands to the oxoiron(IV) porphyrin complex strongly lowers the redox potential, which is in disagreement with experimental observations. This important discrepancy is discussed.

The heterobimetallic complexes [{UO2Ln(py)2(L)}2], combining a singly reduced uranyl cation and a rare-earth trication in a binucleating polypyrrole Schiff-base macrocycle (Pacman) and bridged through a uranyl oxo-group, have been prepared for Ln = Sc, Y, Ce, Sm, Eu, Gd, Dy, Er, Yb, and Lu. These compounds are formed by the single-electron reduction of the Pacman uranyl complex [UO2(py)(H2L)] by the rare-earth complexes Ln(III)(A)3 (A = N(SiMe3)2, OC6H3Bu(t)2-2,6) via homolysis of a Ln-A bond. The complexes are dimeric through mutual uranyl exo-oxo coordination but can be cleaved to form the trimetallic, monouranyl "ate" complexes [(py)3LiOUO(μ-X)Ln(py)(L)] by the addition of lithium halides. X-ray crystallographic structural characterization of many examples reveals very similar features for monomeric and dimeric series, the dimers containing an asymmetric U2O2 diamond core with shorter uranyl U═O distances than in the monomeric complexes. The synthesis by Ln(III)-A homolysis allows [5f(1)-4f(n)]2 and Li[5f(1)-4f(n)] complexes with oxo-bridged metal cations to be made for all possible 4f(n) configurations. Variable-temperature SQUID magnetometry and IR, NIR, and EPR spectroscopies on the complexes are utilized to provide a basis for the better understanding of the electronic structure of f-block complexes and their f-electron exchange interactions. Furthermore, the structures, calculated by restricted-core or all-electron methods, are compared along with the proposed mechanism of formation of the complexes. A strong antiferromagnetic coupling between the metal centers, mediated by the oxo groups, exists in the U(V)Sm(III) monomer, whereas the dimeric U(V)Dy(III) complex was found to show magnetic bistability at 3 K, a property required for the development of single-molecule magnets.

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).

Methylation reactions of gaseous elementary mercury by halogen containing molecules such as halogenomethane species CH(3)X (with X = Cl, Br, and I) and the dimethylchlorinium ion CH(3)ClCH(3)(+) were investigated at the density functional level. With CH(3)X, the reaction is predicted to be almost athermic and kinetically demanding for a thermal reaction. The reaction can proceed photochemically in the visible range; therefore sunlight may increase the reaction rate. These results compare well with the experimental data. Consecutive methylation of the CH(3)HgX products (with X = Cl, Br, and I) and subsequent formation of CH(3)HgCH(3) were also studied. These reactions are predicted to be kinetically inaccessible and thermodynamically unfavorable. With CH(3)ClCH(3)(+), the reaction is predicted to be athermic but kinetically easy. This is due to the suitability of the methyl transfer reagent. Geometrical and electronic data were systematically analyzed in order to rationalize the results.