Oxidation-induced ambiphilicity triggers N-N bond formation and dinitrogen release in octahedral terminal molybdenum(v) nitrido complexes.

Coupling of octahedral, terminal d molybdenum(v) nitrido complexes supported by a dianionic pentadentate ligand N-N bond formation to give μ-dinitrogen complexes was found to be thermodynamically feasible but faces significant kinetic barriers. However, upon oxidation, a kinetically favored nucleophilic/electrophilic N-N bond forming mechanism was enabled to give monocationic μ-dinitrogen dimers. Computational and experimental evidence for this "oxidation-induced ambiphilic nitrido coupling" mechanism is presented.

A molecular extraction process for vanadium based on tandem selective complexation and precipitation.

Recycling vanadium from alternative sources is essential due to its expanding demand, depletion in natural sources, and environmental issues with terrestrial mining. Here, we present a complexation-precipitation method to selectively recover pentavalent vanadium ions, V(V), from complex metal ion mixtures, using an acid-stable metal binding agent, the cyclic imidedioxime, naphthalimidedioxime (HCID). HCID showed high extraction capacity and fast binding towards V(V) with crystal structures showing a 1:1 M:L dimer, [V(O)(CHNO)], 1, and 1:2 M:L non-oxido, [V(CHNO)] complex, 2.

Ruthenium polyhydrides supported by rigid PCP pincer ligands: dynamic behaviour and reactions with CO.

Two rigid β-elimination immune PCP pincer ligands, differing in their electron donor properties by variation of the substitution pattern on the aromatic linker arms, were complexed to ruthenium to form the dichlorides LRRuCl2 (R = H or NMe). These compounds were converted to hydrido chlorides by treatment with dihydrogen (H) and a base. By converting to -butoxide derivatives under an atmosphere of H, the poly hydride PCP complexes LHRRu(H)3 compounds were generated.

Microporous Metal-Phosphonates with a Novel Orthogonalized Linker and Complementary Guests: Insights for Trivalent Metal Complexes from Divalent Metal Complexes.

The reliable self-assembly of microporous metal-phosphonate materials remains a longstanding challenge. This stems from, generally, more coordination modes for the functional group allowing more dense structures, and stronger bonding driving less crystalline products. Here, a novel orthogonalized aryl-phosphonate linker, 1,3,5-tris(4'-phosphono-2',6'-dimethylphenyl) benzene (H L3) has been used to direct formation of open frameworks.

Rhenium(I)-tricarbonyl complexes with methimazole and its selenium analogue: Syntheses, characterization and cell toxicity.

This study explores the effect of a thione/selone ligand on the cell toxicity (in vitro) and light activity of diimine Re(CO) complexes. Six rhenium(I) complexes with general formula fac-[Re(CO)(N,N')X] were prepared, where X = 2-mercapto-1-methylimidazole (methimazole; MMI), and 1-methylimidazole-2-selone (MSeI); N,N' = 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmphen). Their triflate salts were characterized using single-crystal X-ray diffraction, H, C and 2D NMR, UV-vis and vibrational spectroscopy.

Electrocatalyst decomposition pathways: torsional strain in a second sphere proton relay shuts off CORR in a Re(2,2'-bipyridyl)(CO)X type electrocatalyst.

Group 7 tris(carbonyl) bipyridine complexes have been well explored as important CO reduction reaction (CORR) electrocatalysts and now represent an excellent platform for catalyst design. Recent synthetic focus has been on the installation of proton sources/relays within the primary/secondary coordination sphere. These proton sources have been implicated in directly assisting catalysis by acting as shuttles for proton transfer or through the stabilization of transition states through hydrogen bonding.

Unexpected Formation and Potent Antioxidant Activity of Macrocyclic Dimers Containing Disulfide and Selenide Groups.

During attempts to prepare spirodithiaselenuranes as GPx mimetics, a series of unexpected dimeric macrocycles was obtained, each containing two selenide and two disulfide moieties in rings ranging from 18- to 26-membered. The products showed potent GPx-like activity in an NMR assay based on their ability to catalyze the reduction of hydrogen peroxide with benzyl thiol. The high catalytic activity was attributed to transannular effects during selenide to selenoxide oxidation.

A Mesoionic Carbene-Pyridine Bidentate Ligand That Improves Stability in Electrocatalytic CO Reduction by a Molecular Manganese Catalyst.

Tricarbonyl Group 7 complexes have a longstanding history as efficacious CO electroreduction catalysts. Typically, these complexes feature an auxiliary 2,2'-bipyridine ligand that assists in redox steps by delocalizing the electron density into the ligand orbitals. While this feature lends to an accessible redox potential for CO electroreduction, it also presents challenges for electrocatalysis with Mn because the electron density is removed from metal-ligand bonding orbitals.

Identification of ligand linkage vectors for the development of p300/CBP degraders.

To develop new degrader molecules from an existing protein ligand a linkage vector must be identified and then joined with a suitable E3 ligase without disrupting binding to the respective targets. This is typically achieved through empirically evaluating the degradation efficacy of a series of synthetic degraders. Our strategy for determining optimal linkage sites utilises biotinylated protein ligands, linked potential conjugation sites of an inhibitor to confirm whether target protein is maintained after forming a conjugate.

Spontaneous Ammonia Activation Through Coordination-Induced Bond Weakening in Molybdenum Complexes of a Dianionic Pentadentate Ligand Platform.

Ammonia oxidation catalyzed by molecular compounds is of current interest as a carbon-free source of dihydrogen. Activation of N-H bonds through coordination to transition metal centers is a key reaction in this process. We report the substantial activation of ammonia via reaction with low-valent molybdenum complexes of a diborate pentadentate ligand system.

Bis[cyclic (alkyl)(amino)carbene] isomers: Stable -bis(CAAC) facile olefin formation for -bis(CAAC).

Isomeric bis(aldiminium) salts with a 1,4-cyclohexylene framework were synthesized. The first isolable bis(CAAC) was prepared from the -stereoisomer and its ditopic ligand competency was proven by conversion to iridium(I) and rhodium(I) complexes. Upon deprotonation, the -isomer yielded an electron rich olefin a classic, proton-catalyzed pathway.

Orthogonalization of Polyaryl Linkers as a Route to More Porous Phosphonate Metal-Organic Frameworks.

The coordinative pliancy of the phosphonate functional group means that metal-phosphonate materials often self-assemble as well-packed structures with minimal porosity, as efficient inter-ligand packing is enabled. Here, we report a multistep synthesis of a novel aryl-phosphonate linker with an orthogonalized ligand core, 1,3,5-tris(4'-phosphonophenyl)-2,4,6-trimethylbenzene (H L2) designed to form more open structures. A series of crystalline metal-phosphonate frameworks (CALF-35 to -39) have been assembled by coordinating to divalent metals (Ba, Sr, Ca, Mg, Zn).

Green Solvent-Processible N-H-Functionalized Perylene Diimide Materials for Scalable Organic Photovoltaics.

The growing demand for organic electronic devices warrants further development of the scalability and green solvent processibility of π-conjugated materials. Perylene diimide (PDI)-based materials have shown impressive performance as interlayers for electronic devices due to a low energy and high charge mobility in films. The next step in the development of these materials is the transition toward scalable production and the fabrication of devices under ambient conditions.

Regioselective Synthesis of C3-Hydroxyarylated Pyrazoles.

Pyrazoles are ubiquitous structures in medicinal chemistry. We report the first regioselective route to C3-hydroxyarylated pyrazoles obtained through reaction of pyrazole -oxides with arynes using mild conditions. Importantly, this method does not require the C4 and C5 positions of the pyrazole to be functionalized to observe regioselectivity.

Lowering Electrocatalytic CO Reduction Overpotential Using N-Annulated Perylene Diimide Rhenium Bipyridine Dyads with Variable Tether Length.

We report the design, synthesis, and characterization of four N-annulated perylene diimide (NPDI) functionalized rhenium bipyridine [Re(bpy)] supramolecular dyads. The Re(bpy) scaffold was connected to the NPDI chromophore either directly [] or via an ethyl [], butyl [], or hexyl [] alkyl-chain spacer. Upon electrochemical reduction in the presence of CO and a proton source, all exhibited significant current enhancement effects, while did not.

Binding of histidine and human serum albumin to dirhodium(II) tetraacetate.

Reactions of the anticancer active dirhodium tetraacetate (1), Rh(AcO) (AcO = CHCOO), with the amino acid histidine (HHis) and human serum albumin (HSA) were monitored over time and different metal: ligand ratios using UV-vis spectroscopy and/or electro-spray ionization mass spectrometry. Initially, histidine formed 1:1 and 1:2 adducts in aqueous solutions. The crystal structure of Rh(AcO)(L-HHis)·2HO (2) confirmed the axial coordination of histidine imidazole groups (average Rh-N 2.

A monoanionic pentadentate ligand platform for scandium-pnictogen multiple bonds.

A new monoanionic pentadentate ligand is designed to accommodate Sc = E bonds (E = N, P). The imido complex is stable enough to isolate and characterize, and reacts rapidly with CO. The phosphinidene, on the other hand, is highly reactive and induces C-C bond cleavage to yield a phosphido-pyridyl complex which also undergoes rapid reacton with CO.

One-Pot Synthesis of Aryl Selenonic Acids and Some Unexpected Byproducts.

The synthesis of aryl selenonic acids was achieved from diverse aryl bromides via a one-pot method involving metalation, selenation, and oxidation with hydrogen peroxide followed by ion exchange to afford the pure products in 77-90% yield. An -hydroxymethyl derivative was found to dehydrate readily, affording the first example of a cyclic selenonic ester, while two minor byproducts were isolated and shown by X-ray crystallography to be mixed salts of aryl selenonic acids with either the corresponding aryl seleninic or selenious acid.

Activation of ammonia and hydrazine by electron rich Fe(ii) complexes supported by a dianionic pentadentate ligand platform through a common terminal Fe(iii) amido intermediate.

We report the use of electron rich iron complexes supported by a dianionic diborate pentadentate ligand system, , for the coordination and activation of ammonia (NH) and hydrazine (NHNH). For ammonia, coordination to neutral (BPzPy)Fe(ii) or cationic [(BPzPy)Fe(iii)] platforms leads to well characterized ammine complexes from which hydrogen atoms or protons can be removed to generate, fleetingly, a proposed (BPzPy)Fe(iii)-NH complex (). DFT computations suggest a high degree of spin density on the amido ligand, giving it significant aminyl radical character.

Rapid synthesis of pomalidomide-conjugates for the development of protein degrader libraries.

Current methods for the preparation of heterobifunctional pomalidomide-conjugates rely on methods that are often low yielding and produce intractable byproducts. Herein we describe our strategy for the reliable and succinct preparation of pomalidomide-linkers which is essential to the formation of these conjugates. We present the preparation of 18 pomalidomide-linkers in high yield compared to current literature methods.

H/D exchange under mild conditions in arenes and unactivated alkanes with CD and DO using rigid, electron-rich iridium PCP pincer complexes.

The synthesis and characterization of an iridium polyhydride complex () supported by an electron-rich PCP framework is described. This complex readily loses molecular hydrogen allowing for rapid room temperature hydrogen isotope exchange (HIE) at the hydridic positions and the α-C-H site of the ligand with deuterated solvents such as benzene-d, toluene-d and THF-d. The removal of 1-2 equivalents of molecular H forms unsaturated iridium carbene trihydride () or monohydride () compounds that are able to create further unsaturation by reversibly transferring a hydride to the ligand carbene carbon.

The effect of sodium thiosulfate on cytotoxicity of a diimine Re(I) tricarbonyl complex.

Recently, diimine Re(i) tricarbonyl complexes have attracted great interest due to their promising cytotoxic effects. Here, we compare the cytotoxicity and cellular uptake of two Re(i) compounds fac-[(Re(CO)3(bpy)(H2O)](CF3SO3) (1) and Na(fac-[(Re(CO)3(bpy)(S2O3)])·H2O (bpy = 2,2'-bipyridine) (2). The Re-thiosulfate complex in 2 was characterized in two solvated crystal structures {Na(fac-[Re(CO)3(bpy)(S2O3)])·1.

Side-on Coordination in Isostructural Nitrous Oxide and Carbon Dioxide Complexes of Nickel.

A nickel complex incorporating an N O ligand with a rare η -N,N'-coordination mode was isolated and characterized by X-ray crystallography, as well as by IR and solid-state NMR spectroscopy augmented by N-labeling experiments. The isoelectronic nickel CO complex reported for comparison features a very similar solid-state structure. Computational studies revealed that η -N O binds to nickel slightly stronger than η -CO in this case, and comparably to or slightly stronger than η -CO to transition metals in general.

Particle size dependence of proton conduction in a cationic lanthanum phosphonate MOF.

A lanthanum(iii) metal-organic framework, PCMOF21-AcO [La(HL)(AcO)·(HO)], with a 3-D network linked by dicationic bis(dimethylphosphonato)bipiperidinium units and both coordinated and free acetate counter anions is reported. PCMOF21-AcO was water stable and showed very good proton conductivity >10 S cm at 85 °C and 95% relative humidity. PCMOF21-AcO also showed a bimodal particle size distribution and so proton conductivity was further examined as a function of particle size.

The Unexpected Role of Se Species in Epoxidations with Benzeneseleninic Acid and Hydrogen Peroxide.

Benzeneperoxyseleninic acid has been proposed as the key intermediate in the widely used epoxidation of alkenes with benzeneseleninic acid and hydrogen peroxide. However, it reacts sluggishly with cyclooctene and instead rapidly decomposes in solution to a mixed selenonium-selenonate salt that was identified by X-ray absorption and Se NMR spectroscopy, as well as by single crystal X-ray diffraction. This process includes a selenoxide elimination of the peroxyseleninic acid with liberation of oxygen and additional redox steps.