A series of isostructural tetravalent cerium and thorium parent amide (NH2-) complexes were synthesized and characterized. The electronic structure of the M-N(amide) bond was investigated using 15N NMR spectroscopy and DFT calculations in a comparative study of the Na-capped complexes [Na(OEt2)2][M(NH2)(TriNOx)][BArF4], M = Ce (3-Ce), Th (3-Th). The 15N(amide) resonance in 3-Ce was observed at δ = 192 ppm, approximately 95 ppm downfield of the corresponding resonance in 3-Th (δ = 97 ppm). Computational analysis found that the spin-orbit (SO) heavy atom effect on the amide nitrogen NMR shift was relatively small, and comparable, at ΔSO = 12/16 ppm for 3-Ce/3-Th. The observed large difference in the 15N chemical shift for 3-Ce/3-Th is primarily due to differences in paramagnetic shielding generated by the amide lone pairs.

Selective oxidation of metal‐carbon bonds is arguably one of the most important reactions in modern chemistry. In this work, we report the synthesis and the reactivity of a titanium alkyl complex [(TriNOx)Ti(CH 2 SiMe 3 )] (TriNOx 3− = [(2‐ t BuNO)C 6 H 4 CH 2 ] 3 N) 3– ) that was found to undergo an internal rearrangement through an oxy‐insertion into the Ti─C bond facilitated by one of the hydroxylaminato moieties of the supporting TriNOx 3− ligand. Experimental and computational studies are in agreement with an organometallic Baeyer–Villiger‐type mechanism. Furthermore, stepwise dealkoxylation, reoxidation, and alkylation of the resulting complex allowed for closing a synthetic cycle and regenerating the initial starting complex. This work demonstrates the unique ability of the TriNOx 3− ligand to mediate and manage O‐atoms in the coordination sphere of a titanium cation and delineates a new type of metal‐ligand cooperativity through a H eteroatom‐ T ransfer L igand (HTL) platform.

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(Li2μ-N)Ce(TriNOx)][BArF4] is reported, the first example of a molecular cerium-nitride. The compound was isolated by deprotonating a monometallic cerium(IV)-ammonia complex: [CeIV(NH3)(TriNOx)][BArF4]. The average Ce═N bond length of [(TriNOx)Ce(Li2μ-N)Ce(TriNOx)][BArF4] was 2.117(3) Å. Vibrational studies of the 15N-isotopomer exhibited a shift of the Ce═N═Ce asymmetric stretch from ν = 644 cm-1 to 640 cm-1, and X-ray spectroscopic studies confirm the +4 oxidation state of cerium. Computational analyses showed strong involvement of the cerium 4f shell in bonding with overall 16% and 11% cerium weight in the σ- and π-bonds of the Ce═N═Ce fragment, respectively.

A series of thorium anilide compounds [ThNHArR(TriNOx)] (R = para-OCH3 (1-ArOMe), para-H (1-ArH), para-Cl (1-ArCl), para-CF3 (1-Ar4-CF3), TriNOx3- = tris(2-tert-butylhydroxylaminato)benzylamine), and their corresponding imido compounds [Li(DME)][Th═NArR(TriNOx)] (2-ArR) as well as the alkyl congeners [ThNHAd(TriNOx)] (1-Ad) and [Li(DME)][Th═NAd(TriNOx)] (2-Ad), have been prepared. The para-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 13C{1H} NMR chemical shifts of the ipso-C atom of the ArR moiety. Room temperature, solution-state luminescence of the four new thorium imido compounds, along with the previously reported [Li(THF)2][Th═NAr3,5-CF3(TriNOx)] (2-Ar3,5-CF3) and [Li(THF)(Et2O)][Ce═NAr3,5-CF3(TriNOx)] (3-Ar3,5-CF3) have been described. Among these complexes, 2-Ar3,5-CF3 demonstrated the most intense luminescence feature with excitation at 398 nm and emission at 453 nm. The luminescence measurements, together with a time-dependent density functional theory (TD-DFT) study, helped uncover an intra-ligand n → π* transition that was assigned as the origin of the bright blue luminescence; 3-Ar3,5-CF3 has an 1.2 eV redshift in excitation energy compared with its proligand. The weak luminescence of other derivatives (2-ArR and 3-Ar3,5-CF3) was attributed to non-radiative decay from low-lying excited states originating from inter-ligand transitions (2-ArR) or ligand-to-metal charge transfer bands (3-Ar3,5-CF3). Overall, the results expand the range of the thorium imido organometallic compounds and demonstrate that thorium(IV) complexes can support strong ligand luminescence. The results also demonstrate the utility of applying a Th(IV) center for tuning the n → π* luminescence energy and intensity of an associated imido moiety.

The synthesis of iron complexes supported by a mixed phosphine-lutidine-iminophosphorane (PPyNP) ligand was carried out. While bidentate κ2-N,N coordination was observed for FeCl2, pincer coordination modes were adopted at cationic iron centers, either through dechlorination of [LFe(PPyNP)Cl2] (1) or direct coordination of PPyNP to Fe(OTf)2. Reaction with tert-butylisocyanide gave access to the diamagnetic octahedral complex [Fe(PPyNP)(CNtBu)3]X2 (X = OTf (4), Cl (4')). Both 1 and 4 were shown to undergo deprotonation of the phosphinomethyl group, but the resulting complexes were not active for the dehydrogenative coupling of hexan-1-ol. The hydrosilylation of acetophenones was catalyzed at room temperature with 1 mol% of a catalyst generated in situ from cationic PPyNP-supported iron triflate complexes and KHBEt3.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

A selective separation of the critical metals tantalum and niobium was accomplished from π-bonding-based reactivity differences of imido complexes. New insights into Ta/Nb separations were gained through detailed kinetic and computational studies.

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 N-tert-butyl-N-(pyridin-2-yl)hydroxylaminato, [2-( t BuNO)py]-(interchangeable hereafter with [( t BuNO)py]-), a ligand which was previously found to impart remarkable stability to cerium in the +4 oxidation state. An[( t BuNO)py]4 (An = Pu, 1; Np, 2) have been synthesized, characterized by X-ray diffraction, X-ray absorption, 1H NMR and UV-vis-NIR spectroscopies, and cyclic voltammetry, along with computational modeling and analysis. In the case of Pu, oxidation of Pu(iii) to Pu(iv) was observed upon complexation with the [( t BuNO)py]- ligand. The Pu complex 1 and Np complex 2 were also isolated directly from Pu(iv) and Np(iv) precursors. Electrochemical measurements indicate that a Pu(iii) species can be accessed upon one-electron reduction of 1 with a large negative reduction potential (E1/2 = -2.26 V vs. Fc+/0). Applying oxidation potentials to 1 and 2 resulted in ligand-centered electron transfer reactions, which is different from the previously reported redox chemistry of UIV[( t BuNO)py]4 that revealed a stable U(v) product. Treatment of an anhydrous Am(iii) precursor with the [( t BuNO)py]- ligand did not result in oxidation to Am(iv). Instead, the dimeric complex [AmIII(μ2-( t BuNO)py)(( t BuNO)py)2]2 (3) was isolated. Complex 3 is a rare example of a structurally characterized non-aqueous Am-containing molecular complex prepared using inert atmosphere techniques. Predicted redox potentials from density functional theory calculations show a trivalent accessibility trend of U(iii) < Np(iii) < Pu(iii) and that the higher oxidation states of actinides (i.e., +5 for Np and Pu and +4 for Am) are not stabilized by [2-( t BuNO)py]-, in good agreement with experimental observations.

Glutarimide-dioxime, a proligand known for its strongly electron-donating properties that has been studied for applications in uranium-sequestration from seawater, is considered here for stabilization of the cerium(iv) cation.

The reactivity of alkali metal capped Ce(iv) imido compounds [M(DME)2][Ce[double bond, length as m-dash]NArF(TriNOx)] (1-M with M = K, Rb, Cs and ArF = 3,5-bis(trifluoromethyl)phenyl) with CO2 and organic isocyanates has been evaluated. 1-Cs reacted with CO2 to yield an organocarbamate complex. Reaction of 1-K and 1-Rb with organic isocyanates yielded organoureate Ce(iv) complexes.

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, H 3 1·TFA (TFA = trifluoroacetic acid), and complexes 1·RE (RE = La, Nd, Dy). A high-throughput experimentation (HTE) screen was developed to quantitatively determine the precipitation of 1·RE as a function of pH as well as equivalents of H 3 1·TFA. This method rapidly determines optimal conditions for the separation of RE mixtures, while minimizing materials consumption. The HTE-predicted conditions are used to achieve the lab-scale separation of Nd/Dy ( SF Nd/Dy = 213 ± 34) and La/Nd ( SF La/Nd = 16.2 ± 0.2) mixtures in acidic aqueous media.

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-). Collision induced dissociation of the dimer yielded predominantly HTcO(4)and ReO4-, which according to Cooks' kinetic method indicates that the proton affinity (PA) of TcO(4)(-)is greater than that of ReO4-. Density functional theory computations agree with the experimental observation, providing PA[TcO4-] = 300.1 kcal mol(-1)and PA[ReO4-] = 297.2 kcal mol(-1). Attempts to rationalize these relative PAs based on elementary molecular parameters such as atomic charges indicate that the entirety of bond formation and concomitant bond disruption needs to be considered to understand the energies associated with such protonation processes. Although in both the gas and solution phases, TcO(4)(-)is a stronger base than ReO4-, it is noted that the significance of even such qualitative accordance is tempered by the very different natures of the underlying phenomena.

Rare earth metal complexes of the proligand H(3)TriNOx ([(2-(BuNOH)-Bu-t)C6H3CH2](3)N) have been shown to afford separations of simple mixtures of rare earth metal salts. In particular, separations systems were developed for applications to technologically relevant mixtures, e.g., Nd/Dy and Eu/Y for targeted, rare earths recycling chemistry. More recently, it was demonstrated that an electron-donating derivative of the proligand H(3)TriNOx(R) (([(2-(BuNOH)-Bu-t)C6H3RCH2](3)N; R = 5-OMe) influenced electronic and physical properties to effect improved separations. To further probe substituent effects, in the current work, derivatives with electron-donating and-withdrawing groups along the aryl-backbone were synthesized (R = 4-Bu-t, 5-Ph, 4-CF3). The new proligands were coordinated to rare earths (RE) through protonolysis reactions, and the resulting complexes (RE = Nd, Dy) were characterized. Dimerization equilibrium constants and molar solubility were determined where applicable. Overall, the studies indicated that increased electron-donation of the aryl-substituents resulted in an increased driving force for the dimerization of the Nd complexes. This dimerization equilibrium and resultant solubility differences were used to separate mixtures of neodymium/dysprosium as well as mixtures of europium/yttrium. These findings demonstrate the tunability of the TriNOx(3-) framework to achieve tailored RE separations.

A series of uranium(VI)-acetylide complexes of the general formula UVI(O)(C≡C-C6H4-R)[N(SiMe3)2]3, with variation of the para substituent (R = NMe2, OMe, Me, Ph, H, Cl) on the aryl(acetylide) ring, was prepared. These compounds were analyzed by 13C NMR spectroscopy, which showed that the acetylide carbon bound to the uranium(VI) center, U- C≡C-Ar, was shifted strongly downfield, with δ(13C) values ranging from 392.1 to 409.7 ppm for Cl and NMe2 substituted complexes, respectively. These extreme high-frequency 13C resonances are attributed to large negative paramagnetic (σpara) and relativistic spin-orbit (σSO) shielding contributions, associated with extensive U(5f) and C(2s) orbital contributions to the U-C bonding in title complexes. The trend in the 13C chemical shift of the terminal acetylide carbon is opposite that observed in the series of parent (aryl)acetylenes, due to shielding effects of the para substituent. The 13C chemical shifts of the acetylide carbon instead correlate with DFT computed U-C bond lengths and corresponding QTAIM delocalization indices or Wiberg bond orders. SQUID magnetic susceptibility measurements were indicative of the Van Vleck temperature independent paramagnetism (TIP) of the uranium(VI) complexes, suggesting a magnetic field-induced mixing of the singlet ground-state (f0) of the U(VI) ion with low-lying (thermally inaccessible) paramagnetic excited states (involved also in the perturbation-theoretical treatment of the unusually large paramagnetic and SO contributions to the 13C shifts). Thus, together with reported data, we demonstrate that the sensitive 13C NMR shifts serve as a direct, simple, and accessible measure of uranium(VI)-carbon bond covalency.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Phosphoryl ligands of the general formula O═PR3 (R = Me, OMe, Et, nBu, Ph, iPr, NMe2) were coordinated to [Nd(TriNOx)] (TriNOx3– = ([(2-tBuNO)C6H4CH2]3N)3–), and the resulting complexes were characterized. Solution equilibrium constants for each complex were determined, demonstrating a large range for phosphoryl ligands’ Lewis basicity. Thermogravimetric analyses provided evidence for the qualitative thermodynamic preference of phosphoryl ligands for [Nd(TriNOx)] over the dysprosium analogue. These findings were exploited for the separation of binary mixtures of neodymium/dysprosium and lanthanum/neodymium. Implementation of phosphoryl ligands in the TriNOx separation system expands its scope and demonstrates a fundamentally different mode for separating rare-earth cations based on adducts with neutral donors.