Low Part-Per-Trillion, Humidity Resistant Detection of Nitric Oxide Using Microtoroid Optical Resonators.

The nitric oxide radical plays pivotal roles in physiological as well as atmospheric contexts. Although the detection of dissolved nitric oxide in vivo has been widely explored, highly sensitive (i.e.

Development of a Nickel-Catalyzed N-N Coupling for the Synthesis of Hydrazides.

A nickel-catalyzed N-N cross-coupling for the synthesis of hydrazides is reported. -Benzoylated hydroxamates were efficiently coupled with a broad range of aryl and aliphatic amines via nickel catalysis to form hydrazides in an up to 81% yield. Experimental evidence implicates the intermediacy of electrophilic Ni-stabilized acyl nitrenoids and the formation of a Ni(I) catalyst via silane-mediated reduction.

Identifying the Imperative Role of Metal-Olefin Interactions in Catalytic C-O Reductive Elimination from Nickel(II).

We present a series of experimental and computational mechanistic investigations of an unusually facile example of Ni-catalyzed C-O bond formation. Our method, originally reported in 2016, involves the formation of cyclic enol ethers from vinyl iodides bearing pendant alcohol groups. Our findings suggest that the observed reactivity arises from the coordination of the olefin in the vinyl iodide starting material and the enol ether product with Ni(0) intermediates.

Potent strategy towards strongly emissive nitroaromatics through a weakly electron-deficient core.

Nitroaromatics seldom fluoresce. The importance of electron-deficient (n-type) conjugates, however, has inspired a number of strategies for suppressing the emission-quenching effects of the strongly electron-withdrawing nitro group. Here, we demonstrate how such strategies yield fluorescent nitroaryl derivatives of dipyrrolonaphthyridinedione (DPND).

1,2-Addition and cycloaddition reactions of niobium bis(imido) and oxo imido complexes.

The bis(imido) complexes (BDI)Nb(N Bu) and (BDI)Nb(N Bu)(NAr) (BDI = ,'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate; Ar = 2,6-diisopropylphenyl) were shown to engage in 1,2-addition and [2 + 2] cycloaddition reactions with a wide variety of substrates. Reaction of the bis(imido) complexes with dihydrogen, silanes, and boranes yielded hydrido-amido-imido complexes 1,2-addition across Nb-imido π-bonds; some of these complexes were shown to further react insertion of carbon dioxide to give formate-amido-imido products. Similarly, reaction of (BDI)Nb(N Bu) with -butylacetylene yielded an acetylide-amido-imido complex.

Thorium amidates function as single-source molecular precursors for thorium dioxide.

We report the synthesis of four homoleptic thorium(iv) amidate complexes as single-source molecular precursors for thorium dioxide. Each can be sublimed at atmospheric pressure, with the substituents on the amidate ligands significantly impacting their volatility and thermal stability. These complexes decompose via alkene elimination to give ThO2 without need for a secondary oxygen source.

Amidinate Supporting Ligands Influence Molecularity in Formation of Uranium Nitrides.

Uranium nitride complexes are attractive targets for chemists as molecular models for the bonding, reactivity, and magnetic properties of next-generation nuclear fuels, but these molecules are uncommon and can be difficult to isolate due to their high reactivity. Here, we describe the synthesis of three new multinuclear uranium nitride complexes, [U(BCMA)](μ-N)(μ-κ:κ-BCMA) (), [(U(BIMA))(μ-N)(μ-NPr)(K(μ-η:η-CHCHNPr)] (), and [U(BIMA)](μ-N)(μ-κ:κ-BIMA) () (BCMA = ,-bis(cyclohexyl)methylamidinate, BIMA = ,-bis(-propyl)methylamidinate), from U(III) and U(IV) amidinate precursors. By varying the amidinate ligand substituents and azide source, we were able to influence the composition and size of these nitride complexes.

σ or π? Bonding interactions in a series of rhenium metallotetrylenes.

Salt metathesis reactions between a low-valent rhenium(i) complex, Na[Re(η5-Cp)(BDI)] (BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate), and a series of amidinate-supported tetrylenes of the form ECl[PhC(NtBu)2] (E = Si, Ge, Sn) led to rhenium metallotetrylenes Re(E[PhC(NtBu)2])(η5-Cp)(BDI) (E = Si (1a), Ge (2), Sn (4)) with varying extents of Re-E multiple bonding. Whereas the rhenium-stannylene 4 adopts a σ-metallotetrylene arrangement featuring a Re-E single bond, the rhenium-silylene (1a) and -germylene (2) both engage in π-interactions to form short Re-E multiple bonds. Temperature was found to play a crucial role in reactions between Na[Re(η5-Cp)(BDI)] and SiCl[PhC(NtBu)2], as manipulation of reaction conditions led to isolation of an unusual rhenium-silane, (BDI)Re(μ-η5:η1-C5H4)(SiH[PhC(NtBu)2]) (1b) and a dinitrogen bridged rhenium-silylene, (η5-Cp)(BDI)Re(μ-N2)Si[PhC(NtBu)2] (1c), in addition to 1a.

Rational Design of a Uranyl Metal-Organic Framework for the Capture and Colorimetric Detection of Organic Dyes.

A new uranyl containing metal-organic framework, RPL-1: [(UO)(CHO)] HO (RPL for Radiochemical Processing Laboratory), was prepared, structurally characterized, and the solid-state photoluminescence properties explored. Single crystal X-ray diffraction data reveals the structure of RPL-1 consists of two crystallographically unique three dimensional, interpenetrating nets with a 4,3-connected tbo topology. Each net contains large pores with an average width of 22.

Perturbation of Coupling in Carbon-Fluorine Bonds on Coordination to Lewis Acids: A Structural, Spectroscopic, and Computational Study.

A lithiated -terphenyl ligand bearing fluorine atoms at the ortho positions of the flanking aryl rings was synthesized and characterized using single crystal X-ray diffraction, variable-temperature multinuclear NMR spectroscopy, and computational methods. Changes in on coordination to lithium as a spectroscopic observable parametrizing the strength of the C-F···Li interaction are described, and a general, qualitative relationship between C-F bond lengths, Δ values, and the extent of C-F bond activation as a result of Lewis acid coordination is proposed.

Access to Corrole-Appended Persubstituted Benzofurans by a Multicomponent Reaction: The Dual Role of -Chloranil.

A multicomponent reaction among dipyrranes, aryl-propargyl aldehydes, and -chloranil leading to 10-(benzofuran-2-yl)corroles is described. -Chloranil was identified as a crucial reagent playing a twofold role: an oxidant taking part in the formation of the corrole macrocycle and a component undergoing heteroannulation to the incipient 10-arylethynylcorrole. A series of corroles bearing persubstituted benzofuran-2-yl moieties have been synthesized, and their fundamental electronic properties have been studied via UV-vis absorption and fluorescence spectroscopies.

Electronic Structures of Rhenium(II) β-Diketiminates Probed by EPR Spectroscopy: Direct Comparison of an Acceptor-Free Complex to Its Dinitrogen, Isocyanide, and Carbon Monoxide Adducts.

Electron paramagnetic resonance (EPR) studies of the rhenium(II) complex Re(η-Cp)(BDI) (; BDI = ,'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate) have revealed that this species reversibly binds N in solution: flash frozen toluene solutions of disclose entirely different EPR spectra at 10 K when prepared under N versus Ar atmospheres. This observation was additionally verified by the synthesis of stable CO and 2,6-xylylisocyanide (XylNC) adducts of , which display EPR features akin to those observed in the putative N complex. While we found that displays an extremely large value of 3.

Diverse Reactivity of a Rhenium(V) Oxo Imido Complex: [2 + 2] Cycloadditions, Chalcogen Metathesis, Oxygen Atom Transfer, and Protic and Hydridic 1,2-Additions.

We present a wide range of reactivity studies focused on the rhenium(V) oxo imido complex (DippN)(O)Re(BDI) (, Dipp = 2,6-diisopropylphenyl and BDI = ,'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate). This complex, which was previously shown to possess a highly polarized Re oxo moiety, has proven to be a potent nucleophile and a valuable precursor to a variety of rare structural motifs in rhenium coordination complexes. For example, the Re oxo moiety of undergoes [2 + 2] cycloadditions with carbodiimides, isocyanates, carbon dioxide, and isothiocyanates at room temperature.

Uranium Metallocene Azides, Isocyanates, and Their Borane-Capped Lewis Adducts.

Uranium(IV) metallocene complexes (Cp)U(N) (), (Cp)U(NCO) (), and (Cp)U(OTf) () containing the bulky Cp ligand (Cp = tetra(isopropyl)cyclopentadienyl) were prepared directly from reactions between (Cp)UI or (Cp)UI and corresponding pseudohalide salts. The mixed-ligand complex (Cp)U(N)(OTf) () was isolated after heating a 1:1 mixture of and . The coordination of 1 equiv B(CF) to produced the borane-capped azide (Cp)U(N)[(μ-η:η-N)B(CF)] (), while the reaction of 1 equiv B(CF) with yielded (Cp)U(NCO)[(μ-η:η-OCN)B(CF)] () in which the borane-capped cyanate ligand had rearranged to become O-bound to uranium.

Developing scandium and yttrium coordination chemistry to advance theranostic radiopharmaceuticals.

The octadentate siderophore analog 3,4,3-LI(1,2-HOPO), denoted 343-HOPO hereafter, is known to have high affinity for both trivalent and tetravalent lanthanide and actinide cations. Here we extend its coordination chemistry to the rare-earth cations Sc and Y and characterize fundamental metal-chelator binding interactions in solution via UV-Vis spectrophotometry, nuclear magnetic resonance spectroscopy, and spectrofluorimetric metal-competition titrations, as well as in the solid-state via single crystal X-ray diffraction. Sc and Y binding with 343-HOPO is found to be robust, with both high thermodynamic stability and fast room temperature radiolabeling, indicating that 343-HOPO is likely a promising chelator for in vivo applications with both metals.

Structural properties of ultra-small thorium and uranium dioxide nanoparticles embedded in a covalent organic framework.

We report the structural properties of ultra-small ThO and UO nanoparticles (NPs), which were synthesized without strong binding surface ligands by employing a covalent organic framework (COF-5) as an inert template. The resultant NPs were used to observe how structural properties are affected by decreasing grain size within bulk actinide oxides, which has implications for understanding the behavior of nuclear fuel materials. Through a comprehensive characterization strategy, we gain insight regarding how structure at the NP surface differs from the interior.

Facile Activation of Triarylboranes by Rhenium(V) Oxo Imido Complexes.

We report the synthesis and reactivity studies of a pair of rhenium(V) oxo imido complexes. Oxidation of the rhenium(III) terminal oxo ORe(η-DHF)(BDI) (DHF = dihydrofulvalene, BDI = ,'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate) with organic azides R-N (R = Bu, 2,6-diisopropylphenyl) yields the title complexes. Computational studies confirm that the rhenium oxo moieties of these complexes are polarized and correspondingly nucleophilic, owing to the preferential π bonding of the imido ligand to the Re center.

Electron acceptors promote proton-hydride tautomerism in low valent rhenium β-diketiminates.

We report a series of β-diketiminate (BDI) complexes in which tautomeric rhenium(iii) hydride and rhenium(i) protio-BDI species readily interconvert between the solid and solution states. This phenomenon, which is only operative when an electron-accepting ligand is bound to rhenium, was investigated by a combination of experimental and computational methods.

Controlling dinitrogen functionalization at rhenium through alkali metal ion pairing.

The rhenium(i) salt Na[Re(η-Cp)(BDI)] can be cooled in solution under a dinitrogen atmosphere to selectively access complexes containing rhenium(iii) centers bound to direduced, doubly-bonded N (i.e. diazenide) fragments.

Structural, Electrochemical, and Magnetic Studies of Bulky Uranium(III) and Uranium(IV) Metallocenes.

Addition of the potassium salt of the bulky tetra(isopropyl)cyclopentadienyl (Cp) ligand to UI(1,4-dioxane) results in the formation of the bent metallocene uranium(III) complex (Cp)UI (), which is then used to obtain the uranium(IV) and uranium(III) dihalides (Cp)UX () and [cation][(Cp)UX] (, [cation] = [Cp*Co], [EtN], or [MeN]) as mononuclear, donor-free complexes, for X = F, Cl, Br, and I. Interestingly, reaction of with chloride and cyanide salts of alkali metal ions leads to isolation of the chloride- and cyanide-bridged coordination solids [(Cp)U(μ-Cl)Cs] () and [(Cp)U(μ-CN)Na(OEt)] (). Abstraction of the iodide ligand from further enables isolation of the "base-free" metallocenium cation salt [(Cp)U][B(CF)] () and its DME adduct [(Cp)U(DME)][B(CF)] ().

Coordination of 2,2'-(Trifluoroazanediyl)bis(,'-dimethylacetamide) with U(VI), Nd(III), and Np(V): A Thermodynamic and Structural Study.

Thermodynamic properties of the complexation of 2,2'-(trifluoroazanediyl)bis(,'-dimethylacetamide) (CFABDMA) with U(VI), Nd(III), and Np(V) have been studied in 1.0 M NaNO at 25 °C. Equilibrium constants of the complexation were determined by potentiometry and spectrophotometry.

Structural diversity in multinuclear tantalum polyhydrides formed via reductive hydrogenolysis of metal-carbon bonds.

Using H2 as a reducing agent, we demonstrate controlled reduction of tri- and tetramethyl tantalum bis(N-heterocyclic carbene)borate complexes to yield low-valent, multinuclear tantalum polyhydrides. Reaction of a Ta(v)Me3 complex with H2 afforded a bimetallic, hydride-bridged Ta(iv) complex. The analogous reaction of a Ta(v)Me4 complex in benzene or toluene yielded bimetallic Ta(iii) complexes in which both metals are bound to the same face of a μ-η4:η4-arene2- ligand.

H Activation and Direct Access to Terminal Nitride and -P Complexes by an Acceptor-Free Rhenium(II) β-Diketiminate.

The rhenium(II) complex Re(η-Cp)(BDI) (; BDI = ,'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate; Cp = cyclopentadienyl) was subjected to a number of reactivity studies that highlight its unique combination of oxidation state and acceptor-free coordination environment. In the reactions under study we found that this low-valent paramagnetic species yields diamagnetic rhenium(III) or rhenium(V) products, indicating a combination of reducing power and radical character are the primary variables that control its reactivity. Namely, has been found to promote the cleavage of dihydrogen to yield the rhenium(III) hydride Re(H)(η-Cp)(BDI) (), as well as the three-electron reduction of organic azides to yield a rhenium(V) terminal nitride complex NRe(η-Cp)(BDI) (), which features a low-hapticity Cp ligand.

Inducing selectivity and chirality in group IV metal coordination with high-denticity hydroxypyridinones.

The solution- and solid-state interactions between the octadentate siderophore mimic 3,4,3-LI(1,2-HOPO) (343HOPO) and group IV metal ions were investigated using high-resolution mass spectrometry, liquid chromatography, UV-visible spectrophotometry, metal-competition batch titrations, and single crystal X-ray diffraction. 343HOPO forms a neutral 1 : 1 complex, [HfIV343HOPO], that exhibits extreme stability in aqueous solution, with a log β110 value reaching 42.3.