Fe complexes supported by an iminophosphorane ligand: synthesis and reactivity.

The synthesis of iron complexes supported by a mixed phosphine-lutidine-iminophosphorane (PPyNP) ligand was carried out. While bidentate κ-N,N coordination was observed for FeCl, pincer coordination modes were adopted at cationic iron centers, either through dechlorination of [LFe(PPyNP)Cl] (1) or direct coordination of PPyNP to Fe(OTf). Reaction with -butylisocyanide gave access to the diamagnetic octahedral complex [Fe(PPyNP)(CNBu)]X (X = OTf (4), Cl (4')).

Electronic Structure Studies and Photophysics of Luminescent Th(IV) Anilido and Imido Complexes.

A series of thorium anilide compounds [ThNHAr(TriNOx)] (R = -OCH (), -H (), -Cl (), -CF (), TriNOx = (2--butylhydroxylaminato)benzylamine), and their corresponding imido compounds [Li(DME)][Th═NAr(TriNOx)] () as well as the alkyl congeners [ThNHAd(TriNOx)] () and [Li(DME)][Th═NAd(TriNOx)] (), have been prepared. The -substituents on the arylimido moiety were introduced for systematic variation of their electron-donating and withdrawing abilities, changes that were evident in measurements of the C{H} NMR chemical shifts of the -C atom of the Ar moiety. Room temperature, solution-state luminescence of the four new thorium imido compounds, along with the previously reported [Li(THF)][Th═NAr(TriNOx)] () and [Li(THF)(EtO)][Ce═NAr(TriNOx)] () have been described.

Synthesis and Characterization of a Bridging Cerium(IV) Nitride Complex.

Complexes featuring lanthanide-ligand multiple bonds are rare and highly reactive. They are important synthetic targets to understand 4f/5d-bonding in comparison to d-block and actinide congeners. Herein, the isolation and characterization of a bridging cerium(IV)-nitride complex: [(TriNOx)Ce(Liμ-N)Ce(TriNOx)][BAr] is reported, the first example of a molecular cerium-nitride.

Tantalum, easy as Pi: understanding differences in metal-imido bonding towards improving Ta/Nb separations.

The separation and purification of niobium and tantalum, which co-occur in natural sources, is difficult due to their similar physical and chemical properties. The current industrial method for separating Ta/Nb mixtures uses an energy-intensive process with caustic and toxic conditions. It is of interest to develop alternative, fundamental methodologies for the purification of these technologically important metals that improve upon their environmental impact.

Complexation and redox chemistry of neptunium, plutonium and americium with a hydroxylaminato ligand.

There is significant interest in ligands that can stabilize actinide ions in oxidation states that can be exploited to chemically differentiate 5f and 4f elements. Applications range from developing large-scale actinide separation strategies for nuclear industry processing to carrying out analytical studies that support environmental monitoring and remediation efforts. Here, we report syntheses and characterization of Np(iv), Pu(iv) and Am(iii) complexes with -butyl--(pyridin-2-yl)hydroxylaminato, [2-( BuNO)py](interchangeable hereafter with [( BuNO)py]), a ligand which was previously found to impart remarkable stability to cerium in the +4 oxidation state.

Proton affinities of pertechnetate (TcO) and perrhenate (ReO).

The anions pertechnetate, TcO4-, and perrhenate, ReO4-, exhibit very similar chemical and physical properties. Revealing and understanding disparities between them enhances fundamental understanding of both. Electrospray ionization generated the gas-phase proton bound dimer (TcO4-)(H+)(ReO4-).

Reactivity of Ce(iv) imido compounds with heteroallenes.

The reactivity of alkali metal capped Ce(iv) imido compounds [M(DME)][Ce[double bond, length as m-dash]NAr(TriNOx)] (1-M with M = K, Rb, Cs and Ar = 3,5-bis(trifluoromethyl)phenyl) with CO and organic isocyanates has been evaluated. 1-Cs reacted with CO to yield an organocarbamate complex. Reaction of 1-K and 1-Rb with organic isocyanates yielded organoureate Ce(iv) complexes.

High-throughput screening for discovery of benchtop separations systems for selected rare earth elements.

Rare earth (RE) elements (scandium, yttrium, and the lanthanides) are critical for their role in sustainable energy technologies. Problems with their supply chain have motivated research to improve separations methods to recycle these elements from end of life technology. Toward this goal, we report the synthesis and characterization of the ligand tris[(1-hydroxy-2-oxo-1,2-dihydropyridine-3-carboxamido)ethyl]amine, H1·TFA (TFA = trifluoroacetic acid), and complexes 1·RE (RE = La, Nd, Dy).

Magnetic Field Directed Rare-Earth Separations.

The separation of rare-earth ions from one another is challenging due to their chemical and physical similarities. Nearly all rare-earth separations rely upon small changes in ionic radii to direct speciation or reactivity. Herein, we show that the intrinsic magnetic properties of the rare-earth ions impact the separations of light/heavy and selected heavy/heavy binary mixtures.

Halide anion discrimination by a tripodal hydroxylamine ligand in gas and condensed phases.

Electrospray ionization of solutions containing a tripodal hydroxylamine ligand, H3TriNOx ([((2-tBuNOH)C6H4CH2)3N]) denoted as L, and a hydrogen halide HX: HCl, HBr and/or HI, yielded gas-phase anion complexes [L(X)]- and [L(HX2)]-. Collision induced dissociation (CID) of mixed-halide complexes, [L(HXaXb)]-, indicated highest affinity for I- and lowest for Cl-. Structures and energetics computed by density functional theory are in accord with the CID results, and indicate that the gas-phase binding preference is a manifestation of differing stabilities of the HX molecules.

Redox-Driven Chelation and Kinetic Separation of Select Rare Earths Using a Tripodal Nitroxide Proligand.

Separation of the rare-earth (RE) elements (Sc, Y, La-Lu) is challenging because of their similar chemical properties, but is necessary for their applications in renewable energy and electronic device technologies. The development of separation processes driven by kinetic factors represents a new area for this field. Herein, we disclose a novel method of separating select rare earths by reacting RE cyclopentadienides with the triradical species tris(2--butylnitroxyl)benzylamine ().

Multiple Bonding in Lanthanides and Actinides: Direct Comparison of Covalency in Thorium(IV)- and Cerium(IV)-Imido Complexes.

A series of thorium(IV)-imido complexes was synthesized and characterized. Extensive experimental and computational comparisons with the isostructural cerium(IV)-imido complexes revealed a notably more covalent bonding arrangement for the Ce═N bond compared with the more ionic Th═N bond. The thorium-imido moieties were observed to be 3 orders of magnitude more basic than their cerium congeners.

A strategy to improve the performance of cerium(iii) photocatalysts.

A structural modification strategy to improve the photocatalytic performance of a series of cerium(iii) bis(guanidinate) mono(amide) molecular luminophores was demonstrated. Reducing the steric bulkiness of the amide ligand gave rise to two categories of complexes with distinct photophysical and photochemical properties. A structural parameter, the amide cone angle (θ), was applied to differentiate the two categories.

C NMR Shifts as an Indicator of U-C Bond Covalency in Uranium(VI) Acetylide Complexes: An Experimental and Computational Study.

A series of uranium(VI)-acetylide complexes of the general formula U(O)(C≡C-CH-R)[N(SiMe)], with variation of the para substituent (R = NMe, OMe, Me, Ph, H, Cl) on the aryl(acetylide) ring, was prepared. These compounds were analyzed by C NMR spectroscopy, which showed that the acetylide carbon bound to the uranium(VI) center, U- C≡C-Ar, was shifted strongly downfield, with δ(C) values ranging from 392.1 to 409.

Rare earth elements: Mendeleev's bane, modern marvels.

The rare earths (REs) are a family of 17 elements that exhibit pronounced chemical similarities as a group, while individually expressing distinctive and varied electronic properties. These atomistic electronic properties are extraordinarily useful and motivate the application of REs in many technologies and devices. From their discovery to the present day, a major challenge faced by chemists has been the separation of RE elements, which has evolved from tedious crystallization to highly engineered solvent extraction schemes.

Ruthenium complexes featuring cooperative phosphine-pyridine-iminophosphorane (PNN) ligands: synthesis, reactivity and catalytic activity.

The coordination to ruthenium(ii) centres of two phosphine-pyridine-iminophosphorane ligands LR (PPh2CH2(C6H3N)CH2N[double bond, length as m-dash]PR3, R = Ph or Cy) differing by the nature of the substituent of the P[double bond, length as m-dash]N phosphorus was explored. Coordination to [RuCl2(PPh3)3] afforded the complexes [RuLRCl2(PPh3)] that were successfully deprotonated at the acidic phosphinomethyl position. With LCy, coordination led to a mixture of two isomers.

A molecular basis to rare earth separations for recycling: tuning the TriNOx ligand properties for improved performance.

A methoxy-substituted tripodal hydroxylamine ligand, H3TriNOxOMe, was synthesized and coordinated to rare earth cations for separation purposes. Metrics of the resulting complexes were investigated and compared with their parent TriNOx3- counterparts for determination of the molecular basis for the described rare earth separation system. Addition of an electron donating group to the aryl backbone resulted in a more electron rich ligand that increased the equilbrium constant for complex dimerization five-fold.

Exploration of the Solid- and Solution-State Structures and Electrochemical Properties of Ce(atrane) Complexes.

Chemical oxidation of cerium complexes can be unpredictable because of labile metal-ligand bonds leading to ligand redistribution. The use of tripodal frameworks such as silyl-substituted tren ligands (NN' = [N(CHCHN(SiMeBu))]) and a tris(hydroxylaminato) ligand, [((2- BuNO)CHCH)N] (TriNOx), has been shown to mitigate ligand redistribution effects to allow access to tetravalent cerium complexes with different apical ligands. In the current work, the coordination chemistry of Ce with the related tripodal atrane (Hatrane = [N(CHC(CH)OH)]) ligand framework was examined.

C-H Bond Addition across a Transient Uranium-Nitrido Moiety and Formation of a Parent Uranium Imido Complex.

Uranium complexes in the +3 and +4 oxidation states were prepared using the anionic PN (PN = ( N-(2-(diisopropylphosphino)-4-methylphenyl)-2,4,6-trimethylanilide) ligand framework. New complexes include the halide starting materials, (PN)UI (1) and (PN)UCl (2), which both yield (PN)U(N) (3) by reaction with NaN. Compound 3 was reduced with potassium graphite to produce a putative, transient uranium-nitrido moiety that underwent an intramolecular C-H activation to form a rare example of a parent imido complex, [K(THF)][(PN)U(═NH)[ PrP(CHMe)N(CHMeCH)]] (4).

Synthesis and Reactivity of Low-Valent f-Element Iodide Complexes with Neutral Iminophosphorane Ligands.

The coordination and reactivity of simple iodide salts of low-valent f elements [YbI, SmI, TmI, and UI(THF), where THF = tetrahydrofuran] with iminophosphorane (RP═NR') ligands are reported. The studied chelates were observed to adapt their geometry and effectively bind divalent ytterbium and samarium centers, as well as the trivalent uranium cation. The reactivity of the ytterbium adducts with benzophenone was found to be dependent on the steric demand of the supporting iminophosphorane ligand.

Coordination Chemistry of a Strongly-Donating Hydroxylamine with Early Actinides: An Investigation of Redox Properties and Electronic Structure.

Separations of f-block elements are a critical aspect of nuclear waste processing. Redox-based separations offer promise, but challenges remain in stabilizing and differentiating actinides in high oxidation states. The investigation of new ligand types that provide thermodynamic stabilization to high-valent actinides is essential for expanding their fundamental chemistry and to elaborate new separation techniques and storage methods.

Understanding and Controlling the Emission Brightness and Color of Molecular Cerium Luminophores.

Molecular cerium complexes are a new class of tunable and energy-efficient visible- and UV-luminophores. Understanding and controlling the emission brightness and color are important for tailoring them for new and specialized applications. Herein, we describe the experimental and computational analyses for series of tris(guanidinate) (1-8, Ce{(RN)C(N Pr)}, R = alkyl, silyl, or phenyl groups), guanidinate-amide [GA, A = N(SiMe), G = (MeSi)NC(N Pr)], and guanidinate-aryloxide (GOAr, OAr = 2,6-di- tert-butylphenoxide) cerium(III) complexes to understand and develop predictive capabilities for their optical properties.

Functional Synthetic Model for the Lanthanide-Dependent Quinoid Alcohol Dehydrogenase Active Site.

The oxidation of methanol by dehydrogenase enzymes is an essential part of the bacterial methane metabolism cycle. The recent discovery of a lanthanide (Ln) cation in the active site of the XoxF dehydrogenase represents the only example of a rare-earth element in a physiological role. Herein, we report the first synthetic, functional model of Ln-dependent dehydrogenase and its stoichiometric and catalytic dehydrogenation of a benzyl alcohol.

Electronic Structures of Mono-Oxidized Copper and Nickel Phosphasalen Complexes.

Non-innocent ligands render the determination of the electronic structure in metal complexes difficult. As such, a combination of experimental techniques and quantum chemistry are required to correctly elucidate them. This paper deals with the one-electron oxidation of copper(II) and nickel(II) complexes featuring a phosphasalen ligand (Psalen), which differs from salen analogues by the presence of iminophosphorane groups (P=N) instead of imines.

Reduction of Carbonyl Groups by Uranium(III) and Formation of a Stable Amide Radical Anion.

Methyl benzoate, N,N-dimethylbenzamide, and benzophenone were reduced by U [N(SiMe ) ] resulting in uranium(IV) products. Reduction of benzophenone lead to U [OC⋅Ph )][N(SiMe ) ] , (1.1) which forms the dinuclear complex, [N(SiMe ) ] U (OCPhPh-CPh O)U [N(SiMe ) ] (1.