Chemical structure and bonding in a thorium(iii)-aluminum heterobimetallic complex.

Thorium sits at a unique position on the periodic table. On one hand, there is little evidence that its 5f orbitals engage in bonding as they do in other early actinides; on the other hand, its chemistry is distinct from Lewis acidic transition metals. To gain insight into the underlying electronic structure of Th and develop trends across the actinide series, it is useful to study Th(iii) and Th(ii) systems with valence electrons that may engage in non-electrostatic metal-ligand interactions, although only a handful of such systems are known.

A Theoretical Outlook on the Stereoselectivity Origins of Isoselective Zirconocene Propylene Polymerization Catalysts.

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 -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 -symmetric {SBI}-type system, the computation results were in complete agreement with the sole operating chain migratory insertion mechanism.

The role of uranium-arene bonding in HO reduction catalysis.

The reactivity of uranium compounds towards small molecules typically occurs through stoichiometric rather than catalytic processes. Examples of uranium catalysts reacting with water are particularly scarce, because stable uranyl groups form that preclude the recovery of the uranium compound. Recently, however, an arene-anchored, electron-rich uranium complex has been shown to facilitate the electrocatalytic formation of H from HO.

Aqueous Solvation of SmI: A Born-Oppenheimer Molecular Dynamics Density Functional Theory Cluster Approach.

We report the results of Born-Oppenheimer molecular dynamics (BOMD) simulations on the aqueous solvation of the SmI molecule and of the bare Sm cation at room temperature using the cluster microsolvation approach including 37 and 29 water molecules, respectively. The electronic structure calculations were done using the M062X hybrid exchange-correlation functional in conjunction with the 6-31G** basis sets for oxygen and hydrogen. For the iodine and samarium atoms, the Stuttgart-Köln relativistic effective-core potentials were utilized with their associated valence basis sets.

The Nature of the Heavy Alkaline Earth Metal-Hydrogen Bond: Synthesis, Structure, and Reactivity of a Cationic Strontium Hydride Cluster.

The molecular strontium hydride [(MeTACD)Sr(μ-H)][SiPh] (2) was isolated as the dark red benzene solvate 2·CH in 69% yield from the reaction of [Sr(SiPh)(thf)] (1') with (MeTACD)H (1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane). This reaction can be considered as a redox process, with the Brønsted acidic amine proton in (MeTACD)H transformed into the hydride by the anion [SiPh]. Trace amounts of water resulted in the formation of [(MeTACD)Sr(μ-H)(μ-OH)][SiPh] (2*), which cocrystallized with 2.

Dianionic Carbon-Bridged Scandium-Copper/Silver Heterobimetallic Complexes: Synthesis, Bonding, and Reactivity.

Alkylidene-bridged scandium-copper/silver heterobimetallic complexes were synthesized and structurally characterized. The complexes contain different Sc-C and M-C (M=Cu , Ag ) bonds. The reactivity of the scandium-copper heterobimetallic complex was also studied, which reveals that the heterobimetallic complex is a reaction intermediate for the transmetalation of akylidene group from Sc to Cu .

Steric control in the metal-ligand electron transfer of iminopyridine-ytterbocene complexes.

A systematic study of reactions between Cp*Yb(THF) (Cp* = η-CMe, 1) and iminopyridine ligands (IPy = 2,6-PrCHN[double bond, length as m-dash]CH(CHN-R), R = H (2a), 6-CHO (2b), 6-CHS (2c), 6-CH (2d)) featuring similar electron accepting properties but variable denticity and steric demand, has provided a new example of steric control on the redox chemistry of ytterbocenes. The reaction of the unsubstituted IPy 2a with 1, either in THF or toluene, gives rise to the paramagnetic species Cp*Yb(IPy)˙ (3a) as a result of a formal one-electron oxidation of the Yb ion along with IPy reduction to a radical-anionic state. The reactions of 1 with substituted iminopyridines 2b-d, bearing aryl or hetero-aryl dangling arms on the 6 position of the pyridine ring occur in a non-coordinating solvent (toluene) only and afford coordination compounds of a formally divalent ytterbium ion, coordinated by neutral IPy ligands Cp*Yb(IPy) (3b-d).

Kinetic stabilisation of a molecular strontium hydride complex using an extremely bulky amidinate ligand.

Two extremely bulky amidinate ligands, [RC{N(Dip)}{N(Ar)}] (Dip = 2,6-diisopropylphenyl; Ar = CH{C(H)Ph}Pr-2,6,4; R = 1-adamantyl (L), tert-butyl (L)) have been developed and utilised for the kinetic stabilisation of the strontium and magnesium hydride complexes, [LSr(μ-H)] and [LMg(μ-H)] (R = Ad or Bu). The former represents the missing link in the series of dimeric systems, [LAe(μ-H)] (Ae = alkaline earth metal). The structure and bonding of the complexes have been studied by crystallographic, spectroscopic and computational techniques.

Unprecedented Reaction Mode of Phosphorus in Phosphinidene Rare-Earth Complexes: A Joint Experimental-Theoretical Study.

Reactions of trinuclear rare-earth metal complexes bearing functionalized phosphinidene ligand [LLn(μ-Me)(μ-Me)(μ-η:η:η-PCH-o)] (L = [PhC(NCHPr-2,6)], Ln = Y (1a), Lu (1b)) with phenylacetylene, CO, diisopropyl carbodiimide, isocyanide, or PhSSPh lead to the formation of a series of phosphorus-containing products. The reaction of 1 with CS yields two novel P-methyl-phosphindole-2,3-dithiolate dianion complexes, revealing an unusual tandem desulfurization/coupling/cyclization reaction mode of CS. A possible reaction pathway was determined by density functional theory calculations.

Oxygen Atom Transfer to Cationic PCPNi(II) Complexes Using Amine-N-Oxides.

Three PCP pincer ligands differing in the aryl group linking the phosphine arms with the anchoring carbon donor were used to support square planar Ni(II) bromide complexes 1-3. Exchange of the coordinating bromide anion for the more weakly coordinating triflate (OTf) or hexafluoroantimonate (SbF) anions was accomplished by treatment with AgX or TlX salts to give compounds 1-3; compounds 1, 1, 2, 2, 3, and 3 were all characterized by X-ray crystallography. The reactions of these Ni(II) compounds with the amine-N-oxide oxygen atom transfer agents ONMe and ONMePh were explored.

Reversing Conventional Reactivity of Mixed Oxo/Alkyl Rare-Earth Complexes: Non-Redox Oxygen Atom Transfer.

The preferential substitution of oxo ligands over alkyl ones of rare-earth complexes is commonly considered as "impossible" due to the high oxophilicity of metal centers. Now, it has been shown that simply assembling mixed methyl/oxo rare-earth complexes to a rigid trinuclear cluster framework cannot only enhance the activity of the Ln-oxo bond, but also protect the highly reactive Ln-alkyl bond, thus providing a previously unrecognized opportunity to selectively manipulate the oxo ligand in the presence of numerous reactive functionalities. Such trimetallic cluster has proved to be a suitable platform for developing the unprecedented non-redox rare-earth-mediated oxygen atom transfer from ketones to CS and PhNCS.

Reversible Insertion of a C═C Bond into Magnesium(I) Dimers: Generation of Highly Active 1,2-Dimagnesioethane Compounds.

The insertion of 1,1-diphenylethylene into the Mg-Mg bond of two magnesium(I) dimers, [(Nacnac)Mg-] (Ar = CHMe-2,4,6 (Mes); CHEt-2,6 (Dep)), yielding 1,2-dimagnesioethane products, [{(Nacnac)Mg}(μ-CHCPh)], is described. These reactions are readily reversible at room temperature and thus represent the first examples of room-temperature reversible redox processes for s-block metal complexes. The 1,2-dimagnesioethane products are highly activated magnesium alkyls and show unprecedented, uncatalyzed reactivity toward H, CO, and ethylene.

Evidence for single metal two electron oxidative addition and reductive elimination at uranium.

Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido complex in a reaction that satisfies all criteria of a single-metal two-electron oxidative addition.

Organocalcium-mediated nucleophilic alkylation of benzene.

The electrophilic aromatic substitution of a C-H bond of benzene is one of the archetypal transformations of organic chemistry. In contrast, the electron-rich π-system of benzene is highly resistant to reactions with electron-rich and negatively charged organic nucleophiles. Here, we report that this previously insurmountable electronic repulsion may be overcome through the use of sufficiently potent organocalcium nucleophiles.

Nonchelated Phosphoniomethylidene Complexes of Scandium and Lutetium.

The first phosphoniomethylidene complexes of scandium and lutetium, [LLn(CHPPh)X] (L = [MeC(NDIPP)CHC(NDIPP)Me]; Ln = Sc, X = Me, I, TfO; Ln = Lu, X = CHSiMe), have been synthesized and fully characterized. DFT calculations clearly demonstrate the presence of an allylic Ln, C, P π-type interaction in these complexes. X-ray diffraction indicates that the scandium iodide complex has the shortest Sc-C bond length to date (2.

Understanding the Scarcity of Thorium Peroxide Clusters.

The reaction of Th(NO)·5HO with 3 equiv of 2,2',6',2″-terpyridine (terpy) in a mixture of acetonitrile and methanol results in formation of the trinuclear thorium peroxide cluster [Th(O)(terpy)(NO)]. This cluster is assembled via bridging by μ-η:η peroxide anions between thorium centers. It decomposes upon removal from the mother liquor to yield Th(terpy)(NO) and Th(terpy)(NO)(EtOH).

Reduction of a Cerium(III) Siloxide Complex To Afford a Quadruple-Decker Arene-Bridged Cerium(II) Sandwich.

Organometallic multi-decker sandwich complexes containing f-elements remain rare, despite their attractive magnetic and electronic properties. The reduction of the Ce siloxide complex, [KCeL ] (1; L=OSi(OtBu) ), with excess potassium in a THF/toluene mixture afforded a quadruple-decker arene-bridged complex, [K(2.2.

() contributes to natural variation in aluminum resistance in diverse genetic backgrounds of rice ().

Transcription factors (TFs) regulate the expression of other genes to indirectly mediate stress resistance mechanisms. Therefore, when studying TF-mediated stress resistance, it is important to understand how TFs interact with genes in the genetic background. Here, we fine-mapped the aluminum (Al) resistance QTL to a 44-kb region containing six genes.

Metathesis of a U imido complex: a route to a terminal U sulfide.

Herein, we report the synthesis and characterisation of the first terminal uranium(v) sulfide and a related U trithiocarbonate complex supported by sterically demanding tris(-butoxy)siloxide ligands. The reaction of the potassium-bound U imido complex, [U(NAd){OSi(OBu)}K] (), with CS led to the isolation of perthiodicarbonate [K(18c6)][CS] (), with concomitant formation of the U complex, [U{OSi(OBu)}], and S[double bond, length as m-dash]C[double bond, length as m-dash]NAd. In contrast, the reaction of the U imido complex, [K(2.

Formation of Methane versus Benzene in the Reactions of (C Me ) Th(CH ) with [CH PPh ]X (X=Cl, Br, I) Yielding Thorium-Carbene or Thorium-Ylide Complexes.

The reaction of (C Me ) Th(CH ) with the phosphonium salts [CH PPh ]X (X=Cl, Br, I) was investigated. When X=Br and I, two equivalents of methane are liberated to afford (C Me ) Th[CHPPh ]X, rare terminal phosphorano-stabilized carbenes with thorium. These complexes feature the shortest thorium-carbon bonds (≈2.

Accessing Stable Magnesium Acyl Compounds: Reductive Cleavage of Esters by Magnesium(I) Dimers.

The first examples of magnesium acyls, [(Nacnac)Mg{μ-C(Ph)O}(μ-OR)Mg(Nacnac)] (R=Me, tBu or Ph; Nacnac=[HC(MeCNAr) ] ; Ar=C H Me -2,4,6 ( Nacnac), C H Et -2,6 ( Nacnac), C H iPr -2,6 ( Nacnac)), have been prepared by reductive cleavage of a series of esters using dimeric magnesium(I) reducing agents, [{(Nacnac)Mg} ]. Crystallographic studies reveal the complexes to be dimeric, being bridged by both phenyl-acyl and alkoxide/aryloxide fragments. The crystal structures, combined with results of spectroscopic and computational studies suggest that the nature of the acyl ligands within these complexes should be viewed as lying somewhere between anionic umpolung acyl and oxo-carbene.

Synthesis and Reactivity of a Scandium Terminal Hydride: H Activation by a Scandium Terminal Imido Complex.

Dihydrogen is easily activated by a scandium terminal imido complex containing the weakly coordinated THF. The reaction proceeds through a 1,2-addition mechanism, which is distinct from the σ-bond metathesis mechanism reported to date for rare-earth metal-mediated H activation. This reaction yields a scandium terminal hydride, which is structurally well-characterized, being the first one to date.

Incipient class II mixed valency in a plutonium solid-state compound.

Electron transfer in mixed-valent transition-metal complexes, clusters and materials is ubiquitous in both natural and synthetic systems. The degree to which intervalence charge transfer (IVCT) occurs, dependent on the degree of delocalization, places these within class II or III of the Robin-Day system. In contrast to the d-block, compounds of f-block elements typically exhibit class I behaviour (no IVCT) because of localization of the valence electrons and poor spatial overlap between metal and ligand orbitals.