N-Heterocyclic Carbene to Actinide d-Based π-bonding Correlates with Observed Metal-Carbene Bond Length Shortening Versus Lanthanide Congeners.

Comparison of bonding and electronic structural features between trivalent lanthanide (Ln) and actinide (An) complexes across homologous series' of molecules can provide insights into subtle and overt periodic trends. Of keen interest and debate is the extent to which the valence f- and d-orbitals of trivalent Ln/An ions engage in covalent interactions with different ligand donor functionalities and, crucially, how bonding differences change as both the Ln and An series are traversed. Synthesis and characterization (SC-XRD, NMR, UV-vis-NIR, and computational modeling) of the homologous lanthanide and actinide N-heterocyclic carbene (NHC) complexes [M(C5Me5)2(X)(IMe4)] {X = I, M = La, Ce, Pr, Nd, U, Np, Pu; X = Cl, M = Nd; X = I/Cl, M = Nd, Am; and IMe4 = [C(NMeCMe)2]} reveals consistently shorter An-C vs Ln-C distances that do not substantially converge upon reaching Am3+/Nd3+ comparison. Specifically, the difference of 0.064(6) Å observed in the La/U pair is comparable to the 0.062(4) Å difference observed in the Nd/Am pair. Computational analyses suggest that the cause of this unusual observation is rooted in the presence of π-bonding with the valence d-orbital manifold in actinide complexes that is not present in the lanthanide congeners. This is in contrast to other documented cases of shorter An-ligand vs Ln-ligand distances, which are often attributed to increased 5f vs 4f radial diffusivity leading to differences in 4f and 5f orbital bonding involvement. Moreover, in these traditional observations, as the 5f series is traversed, the 5f manifold contracts such that by americium structural studies often find no statistically significant Am3+vs Nd3+ metal-ligand bond length differences.

Carbene Complexes of Plutonium: Structure, Bonding, and Divergent Reactivity to Lanthanide Analogs.

Organoplutonium chemistry was established in 1965, yet structurally authenticated plutonium-carbon bonds remain rare being limited to π-bonded carbocycle and σ-bonded isonitrile and hydrocarbyl derivatives. Thus, plutonium-carbenes, including alkylidenes and N-heterocyclic carbenes (NHCs), are unknown. Here, we report the preparation and characterization of the diphosphoniomethanide-plutonium complex [Pu(BIPMTMSH)(I)(µ-I)]2 (1Pu, BIPMTMSH = (Me3SiNPPh2)2CH) and the diphosphonioalkylidene-plutonium complexes [Pu(BIPMTMS)(I)(DME)] (2Pu, BIPMTMS = (Me3SiNPPh2)2C) and [Pu(BIPMTMS)(I)(IMe4)2] (3Pu, IMe4 = C(NMeCMe)2), thus disclosing non-actinyl transneptunium multiple bonds and transneptunium NHC complexes. These Pu-C double and dative bonds, along with cerium, praseodymium, samarium, uranium, and neptunium congeners, enable lanthanide-actinide and actinide-actinide comparisons between metals with similar ionic radii and isoelectronic 4f5 vs 5f5 electron-counts within conserved ligand fields over 12 complexes. Quantum chemical calculations reveal that the orbital-energy and spatial-overlap terms increase from uranium to neptunium; however, on moving to plutonium the orbital-energy matching improves but the spatial overlap decreases. The bonding picture that emerges is more complex than the traditional picture of the bonding of lanthanides being ionic and early actinides being more covalent but becoming more ionic left to right. Multiconfigurational calculations on 2M and 3M (M = Pu, Sm) account for the considerably more complex UV/vis/NIR spectra for 5f5 2Pu and 3Pu compared to 4f5 2Sm and 3Sm. Supporting the presence of Pu═C double bonds in 2Pu and 3Pu, 2Pu exhibits metallo-Wittig bond metathesis involving the highest atomic number element to date, reacting with benzaldehyde to produce the alkene PhC(H)═C(PPh2NSiMe3)2 (4) and "PuOI". In contrast, 2Ce and 2Pr do not react with benzaldehyde to produce 4.

Impact of Pendent Ammonium Groups on Solubility and Cycling Charge Carrier Performance in Nonaqueous Redox Flow Batteries.

The synthesis, characterization, electrochemical performance, and theoretical modeling of two base-metal charge carrier complexes incorporating a pendent quaternary ammonium group, [Ni(bppn-Me3)][BF4], 3', and [Fe(PyTRENMe)][OTf]3, 4', are described. Both complexes were produced in high yield and fully characterized using NMR, IR, and UV-vis spectroscopies as well as elemental analysis and single-crystal X-ray crystallography. The solubility of 3' in acetonitrile showed a 283% improvement over its neutral precursor, whereas the solubility of complex 4' was effectively unchanged. Cyclic voltammetry indicates an ∼0.1 V positive shift for all waves, with some changes in reversibility depending on the wave. Bulk electrochemical cycling demonstrates that both 3' and 4' can utilize the second more negative wave to a degree, whereas 4' ceases to have a reversible positive wave. Flow cell testing of 3' and 4' with Fc as the posolyte reveals little improvement to the cycling performance of 3' compared with its parent complex, whereas 4' exhibits reductions in capacity decay when cycling either negative wave. Postcycling CVs indicate that crossover is the likely source of capacity loss in complexes 3, 3', and 4' because there is little change in the CV trace. Density functional theory calculations indicate that the ammonium group lowers the HOMO energy in 3' and 4', which may impart stability to cycling negative waves while making positive waves less accessible. Overall, the incorporation of a positively charged species can improve solubility, stored electron density, and capacity decay depending on the complex, features critical to high energy density redox flow battery performance.

Synthesis and comparison of iso-structural f-block metal complexes (Ce, U, Np, Pu) featuring η6-arene interactions.

Reaction of the terphenyl bis(anilide) ligand [{K(DME)2}2LAr] (LAr = {C6H4[(2,6-iPr2C6H3)NC6H4]2}2-) with trivalent chloride "MCl3" salts (M = Ce, U, Np) yields two distinct products; neutral LArM(Cl)(THF) (1M) (M = Np, Ce), and the "-ate" complexes [K(DME)2][(LAr)Np(Cl)2] (2Np) or ([LArM(Cl)2(µ-K(X)2)])∞ (2Ce, 2U) (M = Ce, U) (X = DME or Et2O) (2M). Alternatively, analogous reactions with the iodide [MI3(THF)4] salts provide access to the neutral compounds LArM(I)(THF) (3M) (M = Ce, U, Np, Pu). All complexes exhibit close arene contacts suggestive of η6-interactions with the central arene ring of the terphenyl backbone, with 3M comprising the first structurally characterized Pu η6-arene moiety. Notably, the metal-arene bond metrics diverge from the predicted trends of metal-carbon interactions based on ionic radii, with the uranium complexes exhibiting the shortest M-Ccentroid distance in all cases. Overall, the data presents a systematic study of f-element M-η6-arene complexes across the early actinides U, Np, Pu, and comparison to cerium congeners.

Chlorination of Pu and U Metal Using GaCl3.

The oxidative chlorination of the plutonium metal was achieved through a reaction with gallium(III) chloride (GaCl3). In DME (DME = 1,2-dimethoxyethane) as the solvent, substoichiometric (2.8 equiv) amounts of GaCl3 were added, which consumed roughly 60% of the plutonium metal over the course of 10 days. The salt species [PuCl2(dme)3][GaCl4] was isolated as pale-purple crystals, and both solid-state and solution UV-vis-NIR spectroscopies were consistent with the formation of a trivalent plutonium complex. The analogous reaction was performed with uranium metal, generating a dicationic trivalent uranium complex crystallized as the [UCl(dme)3][GaCl4]2 salt. The extraction of [UCl(dme)3][GaCl4]2 in DME at 70 °C followed by crystallization produced [{U(dme)3}2(µ-Cl3)][GaCl4]3, a product arising from the loss of GaCl3. This method of halogenation worked on a small scale for plutonium and uranium, providing a route to cationic Pu3+ and dicationic U3+ complexes using GaCl3 in DME.

Microstructural and Sensitivity Changes of Neat, Spray-Dried RDX.

Spray drying has recently gained interest in the high explosives (HE) community for the production of novel nanocomposites and well-controlled particle size distributions. However, there is a dearth of information on spray-dried, neat energetic materials. In this work, we correlate the spray drying production parameters to the resulting microstructure and handling sensitivity properties of neat RDX. We demonstrate the capability to fine-tune the particle size distributions for "nanopowder" spray-dried RDX, as well as larger particle size distributions by simply changing the spray dryer setup. We also investigate other physical and chemical changes that RDX undergoes after being processed with spray drying. We characterize these changes with scanning electron microscopy, X-ray diffraction, ultrahigh-performance liquid chromatography, and small-scale sensitivity tests. Interestingly, although the phase and chemical properties are similar before and after spray drying, small-scale sensitivity testing reveals that size reduction of RDX does not follow the typical HE desensitization trends, generally observed for other energetic materials.

Synthesis of Trimethyltriazacyclohexane (Me3tach) Sandwich Complexes of Uranium, Neptunium, and Plutonium Triiodides: (Me3tach)2AnI3.

1,3,5-Trimethyl-1,3,5-triazacyclohexane (Me3tach) readily complexes uranium triiodide to form (Me3tach)2UI3. The complex is soluble in THF and arenes and can function as a source of UI3 to form organometallic U(III) complexes. When dissolved in pyridine (py), (Me3tach)2UI3 forms (Me3tach)UI3(py)2. A related complex with the larger 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3tacn) ligand, namely (Me3tacn)UI3(THF), was synthesized for comparison. Since X-ray quality crystals of (Me3tach)2UI3 can be synthesized in high yield even with small-scale reactions, the system is ideal for extension to transuranium elements. Accordingly, the neptunium and plutonium complexes (Me3tach)2NpI3 and (Me3tach)2PuI3 were synthesized in an analogous manner from NpI3(THF)4 and PuI3(THF)4, respectively.

Isostructural σ-hydrocarbyl phospholide complexes of uranium, neptunium, and plutonium.

σ-Hydrocarbyl complexes of the form [M(η5-PC4Me4)2(µ-η1:η6-CH2Ph)2K(η6-arene)] (M = La, Ce, Pr, U, Np, Pu; arene = benzene or toluene) were synthesised in one-pot reactions from [MI3(THF)4], or [U(BH4)3(toluene)] (M = U). All complexes were examined by multinuclear (1H, 13C{1H}, 31P{1H}) NMR and UV-vis-NIR spectroscopy, as well as single-crystal X-ray diffraction from which molecular metal-phosphorus bonds for Np and Pu, and a σ-hydrocarbyl metal-carbon bond for Pu, have been structurally authenticated.

Hydrazine Energy Storage: Displacing N2 H4 from the Metal Coordination Sphere.

Hydrogen carriers, such as hydrazine (N2 H4 ), may facilitate long duration energy storage, a vital component for resilient grids by enabling more renewable energy generation. Lanthanide coordination chemistry with N2 H4 as well as efforts to displace N2 H4 from the metal coordination sphere to develop an efficient catalytic production cycle were detailed. Modeling the equilibrium of different ligand coordination, it was predicted that strong sigma donor molecules would be required to displace N2 H4 . Monitoring competition experiments with nuclear magnetic resonance confirmed that trimethyl phosphine oxide, dimethylformamide, and dimethyl sulfoxide displaced N2 H4 in large or small lanthanide complexes.

Synthesis, solid-state, solution, and theoretical characterization of an "in-cage" scandium-NOTA complex.

Developing chelators that strongly and selectively bind rare-earth elements (Sc, Y, La, and lanthanides) represents a longstanding fundamental challenge in inorganic chemistry. Solving these challenges is becoming more important because of increasing use of rare-earth elements in numerous technologies, ranging from paramagnets to luminescent materials. Within this context, we interrogated the complexation chemistry of the scandium(III) (Sc3+) trication with the hexadentate 1,4,7-triazacyclononane-1,4,7-triacetic acid (H3NOTA) chelator. This H3NOTA chelator is often regarded as an underperformer for complexing Sc3+. A common assumption is that metalation does not fully encapsulate Sc3+ within the NOTA3- macrocycle, leaving Sc3+ on the periphery of the chelate and susceptible to demetalation. Herein, we developed a synthetic approach that contradicted those assumptions. We confirmed that our procedure forced Sc3+ into the NOTA3- binding pocket by using single crystal X-ray diffraction to determine the Na[Sc(NOTA)(OOCCH3)] structure. Density functional theory (DFT) and 45Sc nuclear magnetic resonance (NMR) spectroscopy showed Sc3+ encapsulation was retained when the crystals were dissolved. Solution-phase and DFT studies revealed that [Sc(NOTA)(OOCCH3)]1- could accommodate an additional H2O capping ligand. Thermodynamic properties associated with the Sc-OOCCH3 and Sc-H2O capping ligand interactions demonstrated that these capping ligands occupied critical roles in stabilizing the [Sc(NOTA)] chelation complex.

Synthesis, characterization, X-ray and electronic structures of diethyl ether and 1,2-dimethoxyethane adducts of molybdenum(IV) chloride and tungsten(IV) chloride.

The bis(diethyl ether) and 1,2-dimethoxyethane (dme) adducts of molybdenum(IV) chloride and tungsten(IV) chloride are valuable starting materials for a variety of synthetic inorganic and organometallic reactions. Despite the broad utility and extensive use of these 6-coordinate complexes, their syntheses remain unoptimized, and their characterization incomplete after more than three decades. While exploring the ligand exchange behaviour of trans-MoCl4(OEt2)2, we obtained single crystals of this red-orange complex and subsequently compared its structural parameters with those of the recently reported trans-WCl4(OEt2)2. Significantly improved procedures for both MoCl4(dme) and WCl4(dme) were developed, and X-ray diffraction data were obtained and analysed. The magnetic properties of the dme adducts were probed, both with Gouy and SQUID magnetometry measurements. The magnetic moment of WCl4(dme) was smaller than that of MoCl4(dme), an observation that we attribute to the greater spin-orbit coupling of tungsten. Electronic structure studies were also conducted to probe the preferential trans configuration of the diethyl ether adducts and to assign the UV-Vis spectra of the dme adducts.

Carbene Complexes of Neptunium.

Since the advent of organotransuranium chemistry six decades ago, structurally verified complexes remain restricted to π-bonded carbocycle and σ-bonded hydrocarbyl derivatives. Thus, transuranium-carbon multiple or dative bonds are yet to be reported. Here, utilizing diphosphoniomethanide precursors we report the synthesis and characterization of transuranium-carbene derivatives, namely, diphosphonio-alkylidene- and N-heterocyclic carbene-neptunium(III) complexes that exhibit polarized-covalent σ2π2 multiple and dative σ2 single transuranium-carbon bond interactions, respectively. The reaction of [NpIIII3(THF)4] with [Rb(BIPMTMSH)] (BIPMTMSH = {HC(PPh2NSiMe3)2}1-) affords [(BIPMTMSH)NpIII(I)2(THF)] (3Np) in situ, and subsequent treatment with the N-heterocyclic carbene {C(NMeCMe)2} (IMe4) allows isolation of [(BIPMTMSH)NpIII(I)2(IMe4)] (4Np). Separate treatment of in situ prepared 3Np with benzyl potassium in 1,2-dimethoxyethane (DME) affords [(BIPMTMS)NpIII(I)(DME)] (5Np, BIPMTMS = {C(PPh2NSiMe3)2}2-). Analogously, addition of benzyl potassium and IMe4 to 4Np gives [(BIPMTMS)NpIII(I)(IMe4)2] (6Np). The synthesis of 3Np-6Np was facilitated by adopting a scaled-down prechoreographed approach using cerium synthetic surrogates. The thorium(III) and uranium(III) analogues of these neptunium(III) complexes are currently unavailable, meaning that the synthesis of 4Np-6Np provides an example of experimental grounding of 5f- vs 5f- and 5f- vs 4f-element bonding and reactivity comparisons being led by nonaqueous transuranium chemistry rather than thorium and uranium congeners. Computational analysis suggests that these NpIII═C bonds are more covalent than UIII═C, CeIII═C, and PmIII═C congeners but comparable to analogous UIV═C bonds in terms of bond orders and total metal contributions to the M═C bonds. A preliminary assessment of NpIII═C reactivity has introduced multiple bond metathesis to transuranium chemistry, extending the range of known metallo-Wittig reactions to encompass actinide oxidation states III-VI.

Pain and Opioid Consumption Following Endoscopic Sinus Surgery: A Prospective Cohort Study.

OBJECTIVES/HYPOTHESIS: Surgeons have a critical role in the current opioid epidemic, and there is a need to prospectively understand patterns of pain and opioid use among patients undergoing endoscopic sinus surgery (ESS). STUDY DESIGN: Prospective observational cohort. METHODS: This was a prospective, observational cohort study that included patients undergoing ESS from November 2019 to March 2020. Demographic data were collected at baseline, as was respondent information regarding preoperative anxiety, pain, and postoperative pain expectations. Opioid use was converted to milligram morphine equivalents (MME). All patients received 10 tablets of 5 mg oxycodone (75 MME). Patients quantified postoperative pain and opioid consumption via telephone follow-up every 48 hours. The primary outcome was total MME utilized. RESULTS: There were 91 patients included in the final cohort. Mean opioid use was 35.2 ± 47.3 MME. There were 29 (32%) patients who did not use any opioids after surgery, and six (7%) patients who required opioid refills. Postoperative opioid use was associated with increased preoperative anxiety (r = 0.41, P < .001), preoperative pain (r = 0.28, P = .007), and expectations for postoperative pain (r = 0.36, P < .001). Increased postoperative pain was only associated with increased opioid use on postoperative days 0-2 (r = 0.33, P = .001) and 3-4 (r = 0.59, P < .001). On multivariate regression, former smoking (ß = 23.4 MME, SE = 10.1, 95% confidence interval [CI]: 3.3-43.5, P = .023) and anxiety (ß = 35.9, SE = 10.2, 95% CI: 15.6-56.3, P < .001) were associated with increased MME. CONCLUSIONS: The majority of patients have minimal opioid use after ESS, and pain appears to influence opioid use within the first 4 days after surgery. Additionally, patients with anxiety may benefit from alternative pain management strategies to mitigate opioid consumption. LEVEL OF EVIDENCE: 3 Laryngoscope, 132:2096-2102, 2022.

2.2.2-Cryptand complexes of neptunium(III) and plutonium(III).

New coordination environments are reported for Np(III) and Pu(III) based on pilot studies of U(III) in 2.2.2-cryptand (crypt). The U(III)-in-crypt complex, [U(crypt)I2][I], obtained from the reaction between UI3 and crypt, is treated with Me3SiOTf (OTf = O3SCF3) in benzene to form the [U(crypt)(OTf)2][OTf] complex. Similarly, the isomorphous Np(III) and Pu(III) complexes were obtained similarly starting from [AnI3(THF)4]. All three complexes (1-An; An = U, Np, Pu) contain an encapsulated actinide in a THF-soluble complex. Absorption spectroscopy and DFT calculations are consistent with 5f3 U(III), 5f4 Np(III), and 5f5 Pu(III) electron configurations.

Repair of Gauged Earlobes: Case Series and Review of Two Techniques According to Size.

BACKGROUND: Earlobe stretching is a common body modification typically performed in individuals under 30 years old. Individuals may later desire restoration of a natural earlobe contour. There is a paucity of literature regarding technique and outcomes for repair of the gauged earlobe defect. AIMS AND OBJECTIVES: The primary aim of this study was to provide a strategy to assess stretched earlobe defects and choose between the repair techniques of de-epithelialization and closure or excision and rotation. The secondary aim of this study was to evaluate complication rates of the two techniques. MATERIALS AND METHODS: Retrospective review of all patients who underwent repair of stretched (gauged) earlobes at a single institution from 2012 to 2019. Patient demographics, maximum earlobe size, motivation for seeking repair, surgical technique, and complication rate were recorded. RESULTS: Fifty-three patients underwent stretched earlobe repair. The average age was 25.9 years old; 60.0% of the patients were male. Defects repaired with de-epithelialization and closure had been stretched to an average of 12.4 (SD = 3.2) mm compared to 29.3 (SD = 10.9) mm for excision and rotation. The minor complication rate was 12.5% with de-epithelialization and 10.8% for excision and rotation. Motivations for seeking repair included a desire to look more professional for work (34.0%), personal preference (30.0%), and joining the military (23.0%). CONCLUSION: Smaller earlobe defects (<15 mm) with nonptotic lobules can be repaired with de-epithelialization and primary closure, whereas larger earlobes (>15.0 mm) with ptotic lobules require excision and rotation. Stretched earlobe repair is a well-tolerated procedure, although a significant number of patients will require minor revisions.

[AnI3(THF)4] (An = Np, Pu) Preparation Bypassing An0 Metal Precursors: Access to Np3+/Pu3+ Nonaqueous and Organometallic Complexes.

Direct comparison of homologous molecules provides a foundation from which to elucidate both subtle and patent changes in reactivity patterns, redox processes, and bonding properties across a series of elements. While trivalent molecular U chemistry is richly developed, analogous Np or Pu research has long been hindered by synthetic routes often requiring scarcely available metallic-phase source material, high-temperature solid-state reactions producing poorly soluble binary halides, or the use of pyrophoric reagents. The development of routes to nonaqueous Np3+/Pu3+ from widely available precursors can potentially transform the scope and pace of research into actinide periodicity. Here, aqueous stocks of An4+ (An = Np, Pu) are dehydrated to well-defined [AnCl4(DME)2] (DME = 1,2-dimethoxyethane), and then a single-step halide exchange/reduction employing Me3SiI produces [AnI3(THF)4] (THF = tetrahydrofuran) in a high to nearly quantitative crystalline yield (with I2 and Me3SiCl as easily removed byproducts). We demonstrate the synthetic utility of these An-iodide molecules, prepared by metal0-free routes, through characterization of archetypal complexes including the tris-silylamide, [Np{N(SiMe3)2}3], and bent metallocenes, [An(C5Me5)2(I)(THF)] (An = Np, Pu)─chosen because both motifs are ubiquitous in Th, U, and lanthanide research. The synthesis of [Np{N(Se═PPh2)2}3] is also reported, completing an isomorphous series that now extends from U to Am and is the first characterized Np3+-Se bond.

Isolation and characterization of a californium metallocene.

Californium (Cf) is currently the heaviest element accessible above microgram quantities. Cf isotopes impose severe experimental challenges due to their scarcity and radiological hazards. Consequently, chemical secrets ranging from the accessibility of 5f/6d valence orbitals to engage in bonding, the role of spin-orbit coupling in electronic structure, and reactivity patterns compared to other f elements, remain locked. Organometallic molecules were foundational in elucidating periodicity and bonding trends across the periodic table1-3, with a twenty-first-century renaissance of organometallic thorium (Th) through plutonium (Pu) chemistry4-12, and to a smaller extent americium (Am)13, transforming chemical understanding. Yet, analogous curium (Cm) to Cf chemistry has lain dormant since the 1970s. Here, we revive air-/moisture-sensitive Cf chemistry through the synthesis and characterization of [Cf(C5Me4H)2Cl2K(OEt2)]n from two milligrams of 249Cf. This bent metallocene motif, not previously structurally authenticated beyond uranium (U)14,15, contains the first crystallographically characterized Cf-C bond. Analysis suggests the Cf-C bond is largely ionic with a small covalent contribution. Lowered Cf 5f orbital energy versus dysprosium (Dy) 4f in the colourless, isoelectronic and isostructural [Dy(C5Me4H)2Cl2K(OEt2)]n results in an orange Cf compound, contrasting with the light-green colour typically associated with Cf compounds16-22.

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 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 (E 1/2 = -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.