-Butyl and Trimethylsilyl Substituents in Nickel Allyl Complexes: Similar but Not the Same.

Metal complexes with -Bu-substituted allyl ligands are relatively rare, especially compared to their conceptually similar trimethylsilyl-substituted analogs. The scarcity partially stems from the few general synthetic entry points for the -Bu versions. This situation was studied through a modified synthesis for the allyl ligand itself and by forming several mono(allyl)nickel derivatives.

p of alcohols dictates their reactivity with reduced uranium-substituted thiomolybdate clusters.

The uranium-substituted thiomolybdate cluster, (Cp*3Mo3S4)UCp*, has been demonstrated as a model for water reduction by single uranium atoms supported on a molybdenum sulfide surface (U@MoS). In this study, the scope of O-H bond activation is expanded through the investigation of the reactivity of various alcohols with differing p values for the -OH proton. The reaction of (Cp*3Mo3S4)UCp* with stoichiometric amounts of methanol, phenol, 2,6-dichlorophenol, and nonafluoro--butyl alcohol affords the corresponding mono-alkoxide species, (Cp*3Mo3S4)Cp*U(OR), a uranium-metalloligand cooperative activation of the O-H bond.

Vanadium Substitution Dictates H Atom Uptake at Lindqvist-type Polyoxotungstates.

Understanding how modification of molecular structures changes the thermochemistry of H atom uptake can provide design criteria for the formation of highly active catalysts for reductive transformations. Herein, we describe the effect of doping an atomically precise polyoxotungstate with vanadium on proton-coupled electron transfer (PCET) reactivity. The Lindqvist-type polyoxotungstate [WO] displays reversible redox chemistry, which was found to be unchanged in the presence of acid, indicating an inability to couple reduction with protonation.

Efficient Dehydration of 1-Phenylethanol to Styrene by Copper(II) and Zinc(II) Fused-Bisoxazolidine Catalysts.

The air-stable copper(II) catalyst [Cu(FOX-L1)(MeCN)][OTf] () is prepared from a fused meso-dipyridylbisoxazolidine (FOX-L1) and CuBr, followed by treatment with AgOTf. The compound is a catalyst for the dehydration of 1-phenylethanol to styrene (+HO) in over 95% yield at 1 mol % catalyst loading. Other alcohols (benzylic, tertiary, or allylic) are also efficiently dehydrated by this catalyst.

Installation of Copper(I) and Silver(I) Sites into TREN-Based Porous Organic Cages via Postsynthetic Metalation.

Porous organic cages (POCs) and metal-organic polyhedra (MOPs) function as zero-dimensional porous materials, able to mimic many functions of insoluble framework materials while offering processability advantages. A popular approach to access tailored metal-based motifs in extended network materials is postsynthetic metalation, which allows metal installation to be decoupled from framework assembly. Surprisingly, this approach has only sparingly been reported for molecular porous materials.

Deactivation Modes in Nickel-Mediated Suzuki-Miyaura Cross-Coupling Reactions Using an NHC-Pyridonate Ligand.

The catalytic activity of an NHC-pyridonate-supported nickel(0) complex for Suzuki-Miyaura coupling of aryl halides was evaluated. Product formation was observed in the absence of a basic additive. However, low turnover numbers resulted from competitive catalyst deactivation.

Bis[2-(isoquinolin-1-yl)phenyl-κ , ](2-phenyl-1-imidazo[4,5-][1,10]phenanthroline-κ ,')iridium(III) hexa-fluorido-phosphate methanol monosolvate.

The title compound, [Ir(CHN)(CHN)]PF·CHOH, crystallizes in the 2/ space group with one monocationic iridium complex, one hexa-fluorido-phosphate anion, and one methanol solvent mol-ecule of crystallization in the asymmetric unit, all in general positions. The anion and solvent are linked to the iridium complex cation hydrogen bonding. All bond lengths and angles fall into expected ranges compared to similar compounds.

Fundamentally intertwined: anharmonic intermolecular interactions dictate both thermal expansion and terahertz lattice dynamics in molecular crystals.

We investigate the anisotropic thermal expansion behavior of a co-crystalline system composed of 4,4'-azopyridine and trimesic acid (TMA-azo). Using variable-temperature single-crystal X-ray diffraction (SC-XRD), low-frequency Raman spectroscopy, and terahertz time-domain spectroscopy (THz-TDS), we observe significant temperature-induced shifting and broadening of the vibrational absorption features, indicating changes in the intermolecular potential. Our findings reveal that thermal expansion is driven by anharmonic interactions and the potential energy topography, rather than increased molecular dynamics.

Effective Alkyl-Alkyl Cross-Coupling with an Iron-Xantphos Catalyst: Mechanistic and Structural Insights.

While iron-catalyzed C(sp)-C(sp) cross-couplings have been widely studied and developed in the last decade, alkyl-alkyl cross-coupling systems with iron remain underdeveloped despite the importance of C(sp)-C(sp) bonds in organic synthesis. A major challenge to the development of these reactions is the current lack of fundamental insight into ligand effects and organoiron intermediates that enable effective alkyl-alkyl couplings. The current study addresses this longstanding limitation using a combination of Fe Mössbauer spectroscopy, SC-XRD (single-crystal X-ray diffraction) and reactivity studies of alkyl-alkyl coupling with iron-Xantphos to define the in situ formed iron-Xantphos intermediates in catalysis.

Mononuclear Fe(III) Schiff base antipyrine complexes for catalytic hydrogen generation.

Mononuclear Fe(III) complexes containing an antipyrine Schiff base ligand were prepared and fully characterized, demonstrating a planar tetradentate coordination geometry. These complexes were found to be active for the hydrogen evolution reaction. Catalysis occurs at -1.

Ru(II)-arene azole complexes as anti-amyloid-β agents.

With the recent clinical success of anti-amyloid-β (Aβ) monoclonal antibodies, there is a renewed interest in agents which target the Aβ peptide of Alzheimer's disease (AD). Metal complexes are particularly well-suited for this development, given their structural versatility and ability to form stabile interactions with soluble Aβ. In this report, a small series of ruthenium-arene complexes were evaluated for their respective ability to modulate both the aggregation and cytotoxicity of Aβ.

Leveraging a reduced polyoxomolybdate-alkoxide cluster for the formation of a stable U(v) sandwich complex.

The synthesis and characterization of a series of (TBA)[M{MoO(OMe)NO}] (M = Zr, Hf, Th, and U) sandwich complexes is reported. A preformed lacunary, Lindqvist-type, polyoxomolybdate-alkoxide cluster provides access to first examples of actinide-polyoxomolybdate sandwich complexes isolated under non-aqueous conditions. Incorporation of metal(iv) cations into this framework was found to "switch on" reversible redox chemistry at the {Mo} ligands, with the Zr and Hf containing complexes accepting up to two electrons, while the Th and U derivates accommodate as many as four additional electrons.

Molecular Models of Atomically Dispersed Uranium at MoS Surfaces Reveal Cooperative Mechanism of Water Reduction.

Single atoms of uranium supported on molybdenum sulfide surfaces (U@MoS) have been recently demonstrated to facilitate the hydrogen evolution reaction (HER) through electrocatalysis. Theoretical calculations have predicted uranium hydroxide moieties bound to edge-sulfur atoms of MoS as a proposed transition state involved in the HER process. However, the isolation of relevant intermediates involved in this process remains a challenge, rendering mechanistic hypotheses unverified.

Unusual S=1 Four-Coordinate Fe(IV) Complexes Supported by Bisamide Ligands: Syntheses, Characterization, and Electronic Structures.

The catalytic relevance of Fe(IV) species in non-heme iron catalysis has motivated synthetic advances in well-defined five- and six-coordinate Fe(IV) complexes for a better understanding of their fundamental electronic structures and reactivities. Herein, we report the syntheses of FeDipp and FeMes, a pair of unusual four-coordinate non-heme formally Fe(IV) complexes with S=1 ground states supported by strongly donating bisamide ligands. By combining spectroscopic characterization and computational modeling, we found that small variations in ligand aryl substituents resulted in substantial changes in both structures and bonding.

Ni(2,2':6',2''-terpyridine): a high-spin octahedral formal Ni(0) complex.

We have synthesised and characterised the complex Ni(tpy) (tpy = 2,2':6',2''-terpyridine). This formally Ni(0) complex is paramagnetic both in the solid state and in solution ( = 2). The crystal structure shows an octahedral geometry, with molecules arranged in independent dimers involving π-stacking between pairs of complexes.

Selective adsorption of fluorinated super greenhouse gases within a metal-organic framework with dynamic corrugated ultramicropores.

Perfluorocompound (PFC) gases play vital roles in microelectronics processing. Requirements for ultra-high purities traditionally necessitate use of virgin sources and thereby hinder the capture, purification, and reuse of these costly gases. Most importantly, gaseous PFCs are incredibly potent greenhouse gases with atmospheric lifetimes on the order of 10-10 years, and thus any environmental emissions have an outsized and prolonged impact on our climate.

Elucidation of Design Criteria for V-based Redox Mediators: Structure-Function Relationships that Dictate Rates of Heterogeneous Electron Transfer.

Redox mediators are attractive solutions for addressing the stringent kinetic stipulations required for efficient energy conversion processes. In this work, we compare the electrochemical properties of four vanadium complexes, namely [V(acac)], [VO(OMe)], [BuN][VO(TRIS)], and [BuN][VO(NO)] in non-aqueous solutions on glassy carbon electrodes. The goal of this study is to investigate the electron transfer kinetics and diffusivity of these compounds under identical experimental conditions to develop an understanding of structure-function relationships that dictate the physicochemical properties of vanadium oxide assemblies.

Synthesis and crystal structures of bis-[1-oxopyridin-2-olato(1-)]bis-(penta-fluoro-phen-yl)silicon(IV)-tetra-hydro-furan-pentane (2/1/1), bis-[1-oxopyridin-2-olato(1-)]bis-(-tol-yl)silicon(IV), and dimesitylbis[1-oxopyridin-2-olato(1-)]silicon(IV).

The neutral organosilicon(IV) complex, (CF)Si(OPO) (OPO = 1-oxopyridin-2-one, CHNO), was synthesized from (CF)Si(OCH) and 2 equiv. of 1-hy-droxy-pyridin-2-one in tetra-hydro-furan (THF). Single crystals grown from the diffusion of -pentane into a THF solution were identified as a THF hemisolvate and an -pentane hemisolvate, (CF)Si(OPO)·0.

Synthesis and Characterization of Isostructural Th(IV) and U(IV) Pyridine Dipyrrolide Complexes.

A series of pyridine dipyrrolide actinide(IV) complexes, (PDP)AnCl(THF) and An(PDP) (An = U, Th, where (PDP) is the doubly deprotonated form of 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1-pyrrol-2-yl)pyridine), have been prepared. Characterization of all four complexes has been performed through a combination of solid- and solution-state methods, including elemental analysis, single crystal X-ray diffraction, and electronic absorption and nuclear magnetic resonance spectroscopies. Collectively, these data confirm the formation of the mono- and bis-ligated species.

Heterometal Dopant Changes the Mechanism of Proton-Coupled Electron Transfer at the Polyoxovanadate-Alkoxide Surface.

The transfer of two H-atom equivalents to the titanium-doped polyoxovanadate-alkoxide, [TiVO(OCH)], results in the formation of a V(III)-OH site at the surface of the assembly. Incorporation of the group (IV) metal ion results in a weakening of the O-H bonds of [TiVO(OH)(OCH)] in comparison to its homometallic congener, [VO(OH)(OCH)], resembling more closely the thermodynamics reported for the one-electron reduced derivative, [VO(OH)(OCH)]. An analysis of early time points of the reaction of [TiVO(OCH)] and 5,10-dihydrophenazine reveals the formation of an oxidized substrate, suggesting that proton-coupled electron transfer proceeds via initial electron transfer from substrate to cluster prior to proton transfer.

Hydrogen Production Using a Nickel Catalyst Combining Redox Activity and Pendent Base Effects.

With the mounting need for clean and renewable energy, catalysts for hydrogen production based on earth abundant elements are of great interest. Herein, we describe the synthesis, characterization, and catalytic activity of two nickel complexes based on the pyridinediimine ligand that possess basic nitrogen moieties of pyridine and imidazole that could potentially serve as pendent bases to enhance catalysis. Although these ligands have previously been reported to be complexed to some metal ions, they have not been applied to nickel.

Molybdenum sulphide clusters as redox-active supports for low-valent uranium.

The preparation of an actinide substituted cubane cluster, (Cp*3Mo3S4)Cp*UI2, and its reduced derivatives are reported. Structural and spectroscopic investigations provide insight into the unique interactions between the actinide and its redox-active molybdenum sulphide metalloligand, serving as a model to study atomically-dispersed, low-valent actinide ions on MoS surfaces. To probe the ability of the assembly to facilitate multielectron small molecule activation, the reactivity of the fully-reduced cluster, (Cp*3Mo3S4)Cp*U, with azobenzene was investigated.

Improved solubility of titanium-doped polyoxovanadate charge carriers for symmetric non-aqueous redox flow batteries.

Non-aqueous redox flow batteries constitute a promising solution for grid-scale energy storage due to the ability to achieve larger cell voltages than can be readily accessed in water. However, their widespread application is limited by low solubility of the electroactive species in organic solvents. In this work, we demonstrate that organic functionalization of titanium-substituted polyoxovanadate-alkoxide clusters increases the solubility of these assemblies over that of their homoleptic congeners by a factor of >10 in acetonitrile.