Overcoming Copper Reduction Limitation in Asymmetric Substitution: Aryl-Radical-Enabled Enantioconvergent Cyanation of Alkyl Iodides.

Cu-catalyzed enantioconvergent cross-coupling of alkyl halides has emerged as a powerful strategy for synthesizing enantioenriched molecules. However, this approach is intrinsically limited by the weak reducing power of copper(I) species, which restricts the scope of compatible nucleophiles and necessitates extensive ligand optimization or the use of complex chiral scaffolds. To overcome these challenges, we introduce an aryl-radical-enabled strategy that decouples the alkyl halide activation step from the chiral Cu center.

C(sp)-H, S-H, and Sn-H Bond Activation with a Cobalt(I) Pincer Complex.

This study focuses on the stoichiometric reactions of {2,6-(PrPO)CH}Co(PMe) with terminal alkynes, thiols, and tin hydrides as part of an effort to develop catalytic, two-electron processes with cobalt. This specific Co(I) pincer complex proves to be effective for cleaving the C(sp)-H, S-H, and Sn-H bonds to give oxidative addition products with the general formula {2,6-(PrPO)CH}CoHX(PMe) (X = alkynyl, thiolate, and stannyl groups) along with the free PMe. These reactions typically reach completion when the substituents on acetylene, sulfur, and tin are electron-withdrawing groups (e.

Ambient Electroreductive Carboxylation of Unactivated Alkyl Chlorides and Polyvinyl Chloride (PVC) Upgrading.

Electrosynthesis of alkyl carboxylic acids upon activating stronger alkyl chlorides at low-energy cost is desired in producing carbon-rich feedstock. Carbon dioxide (CO), a greenhouse gas, has been recognized as an ideal primary carbon source for those syntheses, and such events also mitigate the atmospheric CO level, which is already alarming. On the other hand, the promising upcycling of polyvinyl chloride to polyacrylate is a high energy-demanding carbon-chloride (C-Cl) bond activation process.

Electrosynthesis of Verdoheme and Biliverdin Derivatives Following Enzymatic Pathways.

Artificial syntheses of biologically active molecules have been fruitful in many bioinspired catalysis applications. Specifically, verdoheme and biliverdin, bearing polypyrrole frameworks, have inspired catalyst designs to address energy and environmental challenges. Despite remarkable progress in benchtop synthesis of verdoheme and biliverdin derivatives, all reported syntheses, starting from metalloporphyrins or inaccessible biliverdin precursors, require multiple steps to achieve the final desired products.

Catalytically Relevant Organocopper(III) Complexes Formed through Aryl-Radical-Enabled Oxidative Addition.

Stepwise oxidative addition of copper(I) complexes to form copper(III) species via single electron transfer (SET) events has been widely proposed in copper catalysis. However, direct observation and detailed investigation of these fundamental steps remain elusive owing largely to the typically slow oxidative addition rate of copper(I) complexes and the instability of the copper(III) species. We report herein a novel aryl-radical-enabled stepwise oxidative addition pathway that allows for the formation of well-defined alkyl-Cu species from Cu complexes.

The unanti-cipated oxidation of a tertiary amine in a tetra-cyclic glyoxal-cyclam condensate yielding zinc(II) coordinated to a sterically hindered amine oxide.

The complex, tri-chlorido-(1,4,11-tri-aza-8-azonia-tetra-cyclo-[6.6.2.

Transferrin-inspired iron delivery across the cell membrane using [(LFe)(μ-O)] (L = chlorquinaldol) to harness anticancer activity of ferroptosis.

Although iron is a bio-essential metal, dysregulated iron acquisition and metabolism result in production of reactive oxygen species (ROS) due to the Fenton catalytic reaction, which activates ferroptotic cell death pathways. The lipophilic Fe(III)-chelator chlorquinaldol (L; , 5,7-dichloro-8-hydroxy-2-methylquinoline) strongly favors the formation of a highly stable binuclear Fe(III) complex [(LFe)(μ-O)] (1) that can mimic the function of the Fe(III)-transferrin complex in terms of the strong binding to Fe(III) and facile release of Fe(II) when the metal center is reduced. It should be noted that the cellular uptake of 1 is not transferrin receptor-mediated but enhanced by the high lipophilicity of chlorquinaldol.

Copper-Carbon Homolysis Competes with Reductive Elimination in Well-Defined Copper(III) Complexes.

Despite the recent advancements of Cu catalysis for the cross-coupling of alkyl electrophiles and the frequently proposed involvement of alkyl-Cu(III) complexes in such reactions, little is known about the reactivity of these high-valent complexes. Specifically, although the reversible interconversion between an alkyl-Cu complex and an alkyl radical/Cu pair has been frequently proposed in Cu catalysis, direct observation of such steps in well-defined Cu complexes remains elusive. In this study, we report the synthesis and investigation of alkyl-Cu complexes, which exclusively undergo a Cu-C homolysis pathway to generate alkyl radicals and Cu species.

Unraveling the Solid-State Photoreactivity of Carbonylbis(4,1-Phenylene)dicarbonazidate with Laser Flash Photolysis.

Solid-state photoreactions are generally controlled by the rigid and ordered nature of crystals. Herein, the solution and solid-state photoreactivities of carbonylbis(4,1-phenylene)dicarbonazidate () were investigated to elucidate the solid-state reaction mechanism. Irradiation of in methanol yielded primarily the corresponding amine, whereas irradiation in the solid state gave a mixture of photoproducts.

On the Demise of PPP-Ligated Iron Catalysts in the Formic Acid Dehydrogenation Reaction.

The PPP-ligated iron complexes, -(PPP)FeH(CO) [PPP = (-PrPCH)PR (R = H or Me)], catalyze the dehydrogenation of formic acid to carbon dioxide but lose their catalytic activity over time. This study focuses on the analysis of the species formed from the degradation of -(PPP)FeH(CO) over its course of catalyzing the dehydrogenation reaction. These degradation products include species both soluble and insoluble in the reaction medium.

Earth Abundant Oxidation Catalysts for Removal of Contaminants of Emerging Concern from Wastewater: Homogeneous Catalytic Screening of Monomeric Complexes.

Twenty novel Mn, Fe, and Cu complexes of ethylene cross-bridged tetraazamacrocycles with potentially copolymerizable allyl and benzyl pendant arms were synthesized and characterized. Multiple X-ray crystal structures demonstrate the cis-folded pseudo-octahedral geometry forced by the rigidifying ethylene cross-bridge and show that two cis coordination cites are available for interaction with substrate and oxidant. The Cu complexes were used to determine kinetic stability under harsh acidic and high-temperature conditions, which revealed that the cyclam-based ligands provide superior stabilization with half-lives of many minutes or even hours in 5 M HCl at 50-90 °C.

The curious cases of tetrahydrosalen-type ligands interacting with Ni(II): structures and ligand-based oxidation reactions.

This work centers around the nickel complexes derived from two tetrahydrosalen-type proligands: ,'-bis(2-hydroxybenzyl)--phenylenediamine (Hsalophan) and ,'-bis(2-hydroxy-3-methylbenzyl)--phenylenediamine (Hsalophan_Me). The reaction of Hsalophan with Ni(OAc)·4HO generates a dinuclear complex Ni(Hsalophan)(OAc) or Na[Ni(salophan)(OAc)] when NaOH is added to assist ligand deprotonation. The reaction of Hsalophan_Me with Ni(OAc)·4HO, however, yields a mononuclear complex Ni(Hsalophan_Me).

Light-Mediated Synthesis of 2-(4-Methoxyphenyl)-1-pyrroline via Intramolecular Reductive Cyclization of a Triplet Alkylnitrene.

Irradiation of -methoxyazidobutyrophenone () in methanol yielded 2-(4-methoxyphenyl)-1-pyrroline () and several other photoproducts. However, in the presence of tris(trimethylsilyl)silane (TTMSS), is formed selectively. Transient absorption and ESR spectroscopy verify that the irradiation of forms triplet alkylnitrene through intramolecular energy transfer from the triplet ketone (T).

A Bridge too Far? Comparison of Transition Metal Complexes of Dibenzyltetraazamacrocycles with and without Ethylene Cross-Bridges: X-ray Crystal Structures, Kinetic Stability, and Electronic Properties.

Tetraazamacrocycles, cyclic molecules with four nitrogen atoms, have long been known to produce highly stable transition metal complexes. Cross-bridging such molecules with two-carbon chains has been shown to enhance the stability of these complexes even further. This provides enough stability to use the resulting compounds in applications as diverse and demanding as aqueous, green oxidation catalysis all the way to drug molecules injected into humans.

Synthesis and Characterization of Late Transition Metal Complexes of Mono-Acetate Pendant Armed Ethylene Cross-Bridged Tetraazamacrocycles with Promise as Oxidation Catalysts for Dye Bleaching.

Ethylene cross-bridged tetraazamacrocycles are known to produce kinetically stable transition metal complexes that can act as robust oxidation catalysts under harsh aqueous conditions. We have synthesized ligand analogs with single acetate pendant arms that act as pentadentate ligands to Mn, Fe, Co, Ni, Cu, and Zn. These complexes have been synthesized and characterized, including the structural characterization of four Co and Cu complexes.

Methyl Effects on the Stereochemistry and Reactivity of PPP-Ligated Iron Hydride Complexes.

Iron dihydride complexes are key intermediates in many iron-catalyzed reactions. Previous efforts to study molecules of this type have led to the discovery of a remarkably stable -FeH complex, which is supported by bis[2-(diisopropylphosphino)phenyl]phosphine (PPP) along with CO. In this work, the hydrogen on the central phosphorus has been replaced with a methyl group, and the corresponding iron carbonyl dichloride, hydrido chloride, and dihydride complexes have been synthesized.

Optical sensing of aqueous nitrate anion by a platinum(II) triimine salt based solid state material.

Selective and quantitative measurement of aqueous nitrate (NO) anion is achieved using solid [Pt(Cl-4-tpy)Cl]ClO salt (Cl-4-tpy = 4-chloro-2,2':6'2''-terpyridine), and as the salt supported on controlled porous glass. This detection method relies on the color change of the Pt(II) complex from yellow to red and intense luminescence response upon ClO exchange with NO due to concomitant enhancement of Pt⋯Pt interactions. The spectroscopic response is highly selective for NO over a large range of halides and oxoanions.

Iron Dihydride Complex Stabilized by an All-Phosphorus-Based Pincer Ligand and Carbon Monoxide.

PNP-pincer-stabilized iron carbonyl dihydride complexes are key intermediates in catalytic hydrogenation and dehydrogenation reactions; however, decomposition through these intermediates has been observed. This inspires the development of a PPP-pincer system that may show improved catalyst stability. In this work, bis[2-(diisopropylphosphino)phenyl]phosphine (or PPP) is used to react with FeCl under a carbon monoxide (CO) atmosphere to yield -(PPP)Fe(CO)Cl.

Water's Role in Polymorphic Platinum(II) Complexes.

Solvent plays a vital role in the recrystallization process and resulting crystallinity of materials. This role is of such importance that it can control the stability and utility of materials. In this work, the inclusion of a solvent in the crystalline lattice, specifically water, drastically affects the overall stability of two platinum polymorphs.

Copper-catalyzed carbo-difluoromethylation of alkenes via radical relay.

Organic molecules that contain alkyl-difluoromethyl moieties have received increased attention in medicinal chemistry, but their synthesis in a modular and late-stage fashion remains challenging. We report herein an efficient copper-catalyzed radical relay approach for the carbo-difluoromethylation of alkenes. This approach simultaneously introduces CFH groups along with complex alkyl or aryl groups into alkenes with regioselectivity opposite to traditional CFH radical addition.

Microwave-Assisted Synthesis of Organometallic Rhenium (I) Pentylcarbonato Complexes: New Synthon for Carboxylato, Sulfonato and Chlorido Complexes.

Tricarbonylrhenium(I)(α-diimine) complexes are of importance because of their strong cytotoxic and fluorescence properties. Syntheses of such complexes were achieved through a two-step process. First, the pentylcarbonato complexes, -(CO)(α-diimine)ReOC(O)OCH were synthesized through a microwave-assisted reaction of Re(CO), α-diimine, 1-pentanol and CO in a few hours.

Experimental Evidence of H-N-Fe-H Configurational Requirement for Iron-Based Bifunctional Hydrogenation Catalysts.

Iron hydrides supported by a pincer ligand of the type HN(CHCHPR) (PNP) are versatile hydrogenation catalysts. Previous efforts have focused on using CO as an additional ligand to stabilize the hydride species. In this work, CO is replaced with isocyanide ligands, leading to the isolation of two different types of iron hydride complexes: (PNP)FeH(CNR')(BH) (R = Pr, R' = 2,6-MeCH, Bu; R = Cy, R' = 2,6-MeCH) and [(PNP)FeH(CNBu)]X (X = BPh, Br, or a mixture of Br and BH).

pH-Mediated Colorimetric and Luminescent Sensing of Aqueous Nitrate Anions by a Platinum(II) Luminophore@Mesoporous Silica Composite.

Increased levels of nitrate (NO) in the environment can be detrimental to human health. Herein, we report a robust, cost-effective, and scalable, hybrid material-based colorimetric/luminescent sensor technology for rapid, selective, sensitive, and interference-free NO detection. These hybrid materials are based on a square-planar platinum(II) salt [Pt(tpy)Cl]PF (tpy = 2,2';6',2″-terpyridine) supported on mesoporous silica.

Cracking under Internal Pressure: Photodynamic Behavior of Vinyl Azide Crystals through N Release.

When exposed to UV light, single crystals of the vinyl azides 3-azido-1-phenylpropenone (), 3-azido-1-(4-methoxyphenyl)propenone (), and 3-azido-1-(4-chlorophenyl)propenone () exhibit dramatic mechanical effects by cracking or bending with the release of N. Mechanistic studies using laser flash photolysis, supported by quantum mechanical calculations, show that each of the vinyl azides degrades through a vinylnitrene intermediate. However, despite having very similar crystal packing motifs, the three compounds exhibit distinct photomechanical responses in bulk crystals.