Preparation of High-Purity Ammonium Tetrakis(pentafluorophenyl)borate for the Activation of Olefin Polymerization Catalysts

Homogeneous olefin polymerization catalysts are activated in situ with a co-catalyst ([PhN(Me)₂-H]⁺[B(C₆F₅)₄]⁻ or [Ph₃C]⁺[B(C₆F₅)₄]⁻) in bulk polymerization media. These co-catalysts are insoluble in hydrocarbon solvents, requiring excess co-catalyst (>3 eq.). Feeding the activated species as a solution in an aliphatic hydrocarbon solvent may be advantageous over the in situ activation method. In this study, highly pure and soluble ammonium tetrakis(pentafluorophenyl)borates ([Me(C₁₈H₃₇)₂N-H]⁺[B(C₆F₅)₄]⁻ and [(C₁₈H₃₇)₂NH₂]⁺[B(C₆F₅)₄]⁻) containing neither water nor Cl⁻ salt impurities were prepared easily via the acid–base reaction of [PhN(Me)₂-H]⁺[B(C₆F₅)₄]⁻ and the corresponding amine. Using the prepared ammonium salts, the activation reactions of commercial-process-relevant metallocene (rac-[ethylenebis(tetrahydroindenyl)]Zr(Me)₂ (1-ZrMe₂), [Ph₂C(Cp)(3,6-^tBu₂Flu)]Hf(Me)₂ (3-HfMe₂), [Ph₂C(Cp)(2,7-^tBu₂Flu)]Hf(Me)₂ (4-HfMe₂)) and half-metallocene complexes ([(η⁵-Me₄C₅)Si(Me)₂(κ-N^tBu)]Ti(Me)₂ (5-TiMe₂), [(η⁵-Me₄C₅)(C₉H₉(κ-N))]Ti(Me)₂ (6-TiMe₂), and [(η⁵-Me₃C₇H₁S)(C₁₀H₁₁(κ-N))]Ti(Me)₂ (7-TiMe₂)) were monitored in C₆D₁₂ with ¹H NMR spectroscopy. Stable [L-M(Me)(NMe(C₁₈H₃₇)₂)]⁺[B(C₆F₅)₄]⁻ species were cleanly generated from 1-ZrMe₂, 3-HfMe₂, and 4-HfMe₂, while the species types generated from 5-TiMe₂, 6-TiMe₂, and 7-TiMe₂ were unstable for subsequent transformation to other species (presumably, [L-Ti(CH₂N(C₁₈H₃₇)₂)]⁺[B(C₆F₅)₄]⁻-type species). [L-TiCl(N(H)(C₁₈H₃₇)₂)]⁺[B(C₆F₅)₄]⁻-type species were also prepared from 5-TiCl(Me) and 6-TiCl(Me), which were newly prepared in this study. The prepared [L-M(Me)(NMe(C₁₈H₃₇)₂)]⁺[B(C₆F₅)₄]⁻-, [L-Ti(CH₂N(C₁₈H₃₇)₂)]⁺[B(C₆F₅)₄]⁻-, and [L-TiCl(N(H)(C₁₈H₃₇)₂)]⁺[B(C₆F₅)₄]⁻-type species, which are soluble and stable in aliphatic hydrocarbon solvents, were highly active in ethylene/1-octene copolymerization performed in aliphatic hydrocarbon solvents.     

A Series of Novel Pentagonal-Bipyramidal Erbium(III) Complexes with Acyclic Chelating N3O2 Schiff-Base Ligands: Synthesis,Structure, and Magnetism

A series of six seven-coordinate pentagonal-bipyramidal (PBP) erbium complexes, with acyclic pentadentate [N₃O₂] Schiff-base ligands, 2,6-diacetylpyridine bis-(4-methoxybenzoylhydrazone) [H₂DAPMBH], or 2,6-diacethylpyridine bis(salicylhydrazone) [H₄DAPS], and various apical ligands in different charge states were synthesized: [Er(DAPMBH)(C₂H₅OH)Cl] (1); [Er(DAPMBH)(H₂O)Cl]·2C₂H₅OH (2); [Er(DAPMBH)(CH₃OH)Cl] (3); [Er(DAPMBH)(CH₃OH)(N₃)] (4); [(Et₃H)N]⁺[Er(H₂DAPS)Cl₂]⁻ (5); and [(Et₃H)N]⁺[Y₀.₉₅Er₀.₀₅(H₂DAPS)Cl₂]⁻ (6). The physicochemical properties, crystal structures, and the DC and AC magnetic properties of 1–6 were studied. The AC magnetic measurements revealed that most of Compounds 1–6 are field-induced single-molecule magnets, with estimated magnetization energy barriers, U_eff ≈ 16–28 K. The experimental study of the magnetic properties was complemented by theoretical analysis based on ab initio and crystal field calculations. An experimental and theoretical study of the magnetism of 1–6 shows the subtle impact of the type and charge state of the axial ligands on the SMM properties of these complexes.     

Self-Assembly of Antiferromagnetically-Coupled Copper(II) Supramolecular Architectures with Diverse Structural Complexities

The self-assembly of 2,6-diformyl-4-methylphenol (DFMP) and 1-amino-2-propanol (AP)/2-amino-1,3-propanediol (APD) in the presence of copper(II) ions results in the formation of six new supramolecular architectures containing two versatile double Schiff base ligands (H₃L and H₅L1) with one-, two-, or three-dimensional structures involving diverse nuclearities: tetranuclear [Cu₄(HL²⁻)₂(N₃)₄]·4CH₃OH·56H₂O (1) and [Cu₄(L³⁻)₂(OH)₂(H₂O)₂] (2), dinuclear [Cu₂(H₃L1²⁻)(N₃)(H₂O)(NO₃)] (3), polynuclear {[Cu₂(H₃L1²⁻)(H₂O)(BF₄)(N₃)]·H₂O}_n (4), heptanuclear [Cu₇(H₃L1²⁻)₂(O)₂(C₆H₅CO₂)₆]·6CH₃OH·44H₂O (5), and decanuclear [Cu₁₀(H₃L1²⁻)₄(O)₂(OH)₂(C₆H₅CO₂)₄] (C₆H₅CO₂)₂·20H₂O (6). X-ray studies have revealed that the basic building block in 1, 3, and 4 is comprised of two copper centers bridged through one μ-phenolate oxygen atom from HL²⁻ or H₃L1²⁻, and one μ-1,1-azido (N₃⁻) ion and in 2, 5, and 6 by μ-phenoxide oxygen of L³⁻ or H₃L1²⁻ and μ-O²⁻ or μ₃-O²⁻ ions. H-bonding involving coordinated/uncoordinated hydroxy groups of the ligands generates fascinating supramolecular architectures with 1D-single chains (1 and 6), 2D-sheets (3), and 3D-structures (4). In 5, benzoate ions display four different coordination modes, which, in our opinion, is unprecedented and constitutes a new discovery. In 1, 3, and 5, Cu(II) ions in [Cu₂] units are antiferromagnetically coupled, with J ranging from −177 to −278 cm⁻¹.     

Crystal Structure and Solid-State Packing of 4-Chloro-5H-1,2,3-dithiazol-5-one and 4-Chloro-5H-1,2,3-dithiazole-5-thione

The crystal structure and solid-state packing of 4-chloro-5H-1,2,3-dithiazol-5-one and two polymorphs of 4-chloro-5H-1,2,3-dithiazole-5-thione were analyzed and compared to structural data of similar systems. These five-membered S,N-rich heterocycles are planar with considerable bond localization. All three structures demonstrate tight solid-state packing without voids which is attributed to a rich network of short intermolecular electrostatic contacts. These include S^δ+…N^δ−, S^δ+…O^δ−, S^δ+…Cl^δ− and S^δ+…S^δ− interactions that are well within the sum of their van der Waals radii (∑_VDW). B3LYP, BLYP, M06, mPW1PW, PBE and MP2 were employed to calculate their intramolecular geometrical parameters, the Fukui condensed functions to probe their reactivity, the bond order, Bird Index and NICS(1) to establish their aromaticity.     

SIFT studies of the reactions of H3O+, NO+ and O+2 with a series of volatile carboxylic acids and esters

We report the results of a selected ion flow tube (SIFT) study of the reactions of H₃O⁺, NO⁺ and O⁺₂ with some nine carboxylic acids and eight esters. We assume that all the exothermic proton transfer reactions of H₃O⁺ with all the acid and esters molecules occur at the collisional rate, i.e. the rate coefficients, k, are equal to k_c; then it is seen that k values for most of the NO⁺ and O⁺₂ reactions also are equal to or close to k_c. The major ionic products of the H₃O⁺ reactions with both the acids and esters are the protonated parent molecules, MH⁺, but minor channels are also evident, these being the result of H₂O elimination from the excited (MH⁺)1 in some of the acid reactions and an alcohol molecule elimination (CH₃OH or C₂H₅OH) in some of the ester reactions. The NO⁺ reactions with the acids and esters result in both ion-molecule association producing NO⁺M in parallel with hydroxide ion (OH⁻) transfer with some of the acids, and parallel methoxide ion (CH₃O⁻) and ethoxide ion (C₂H₅O⁻) transfer as appropriate with some of the esters. The O⁺₂ reactions proceed by dissociative charge transfer with the production of two or more ionic fragments of the parent molecules, the different isomeric forms of both the acid and the ester molecules resulting in different product ions.     

Mechanism of OH radical-induced oxidation of <Emphasis Type="Italic">p</Emphasis>-cresol to <Emphasis Type="Italic">p</Emphasis>-methylphenoxyl radical

The OH radical-induced oxidation of p-cresol to p-methylphenoxyl radical was studied in aqueous solution in a wide pH range by means of pulse radiolysis combined with optical spectroscopy. OH-adduct cyclohexadienyl type radicals were identified as intermediates of the reaction. In the acidic pH range the first-order rate coefficient of phenoxyl radical formation was found linearly dependent on the H₃O⁺ concentration yielding a bimolecular rate coefficient of 1.8 × 10⁸ mol^–1 dm³ s^–1. In the alkaline range a linear dependence was found on the OH^– concentration with rate coefficient of 4.9 × 10¹⁰ mol^–1 dm³ s^–1. These findings were interpreted in terms of acid-base catalysis of the H₂O elimination from the OH-adduct. With the time resolution applied, 30 ns, the radical cation p-CH₃C₆H₄OH^+. was not observed as intermediate.     

Revisiting Aromaticity and Chemical Bonding of Fluorinated Benzene Derivatives

The electron delocalization of benzene (C₆H₆) and hexafluorobenzene (C₆F₆) was analyzed in terms of the induced magnetic field, nucleus-independent chemical shift (NICS), and ring current strength (RCS). The computed out-of-plane component of the induced magnetic field at a distance (r) greater than or equal to 1.0 Å above the ring center correlates well (R²>0.99) with the RCS value. According to these criteria, fluorination has two effects on the C₆ skeleton; concomitantly, the resonant effects diminish the π electron delocalization and the inductive effects decrease the charge density at the ring center and therefore reduce the magnitude of the paratropic current generated in this region. The equilibrium between both effects decreases aromaticity in the fluorinated benzene derivatives. These results can be extrapolated to determine the aromaticity of any derivative within the series of fluorinated benzene derivatives (C₆H_(6−n)F_n, where n=1–5).     

Understanding how Lewis acids dope organic semiconductors: a “complex” story

We report on computational studies of the potential of three borane Lewis acids (LAs) (B(C₆F₅)₃ (BCF), BF₃, and BBr₃) to form stable adducts and/or to generate positive polarons with three different semiconducting π-conjugated polymers (PFPT, PCPDTPT and PCPDTBT). Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations based on range-separated hybrid (RSH) functionals provide insight into changes in the electronic structure and optical properties upon adduct formation between LAs and the two polymers containing pyridine moieties, PFPT and PCPDTPT, unravelling the complex interplay between partial hybridization, charge transfer and changes in the polymer backbone conformation. We then assess the potential of BCF to induce p-doping in PCPDTBT, which does not contain pyridine groups, by computing the energetics of various reaction mechanisms proposed in the literature. We find that reaction of BCF(OH₂) to form protonated PCPDTBT and [BCF(OH)]⁻, followed by electron transfer from a pristine to a protonated PCPDTBT chain is highly endergonic, and thus unlikely at low doping concentration. The theoretical and experimental data can, however, be reconciled if one considers the formation of [BCF(OH)BCF]⁻ or [BCF(OH)(OH₂)BCF]⁻ counterions rather than [BCF(OH)]⁻ and invokes subsequent reactions resulting in the elimination of H₂.

Here we report on DFT calculations investigating the mechanistic aspects in doping organic semiconductors by the use of Lewis acids. Our results highlight the role played by the formation of diboron-containing bridged anions in the doping mechanism.     

α-Glycyl cation, radical, and anion (H2NCH+/·/−COOH): Generation and characterization in the gas phase

The title species are synthesized in the gas phase and their unimolecular chemistry is determined by a combination of tandem mass spectrometry methods. Dissociative electron ionization of the α-amino acids valine, leucine, isoleucine, or serine produces the α-glycyl cation, H₂NCH⁺COOH, in high yield and purity. At threshold, this ion dissociates by CO loss to form the proton-bound complex HCNH⁺OH₂ via a tight 1,4-H migration that is associated with a high reverse barrier. After collisional activation, additional channels open, most notably the formation of the complementary and structure-characteristic fragments H₂NCH^+· (ionized aminocarbene) and ⁺COOH and the elimination of OH^·. Charge reversal and neutralization–reionization of H₂NCH⁺COOH conclusively show that α-glycyl anion, H₂NCH⁻COOH, and α-glycyl radical, H₂NCH^·COOH, are stable species residing in deep potential energy wells. In the microsecond time window of the experiments, a small fraction of the α-glycyl radical decomposes by sequential elimination of H₂O and CO. The α-glycyl anions arising by charge reversal of the cation or reionization of the radical partly undergo rearrangement losses of H₂ and H₂O, direct cleavages to ⁻COOH, OH⁻, and H₂N⁻, and consecutive fragmentation of these primary product anions.     

Loss of methyl from [H2CC(OH)?CH3]+˙ ions prepared by electron impact ionization of unstable 2-hydroxypropene

Unstable 2-hydroxpropene was prepared by retro-Diels-Alder decomposition of 5-exo-methyl-5-norbornenol at 800°C/2 × 10^?6 Torr. The ionization energy of 2-hydroxypropene was measured as 8.67±0.05 eV. Formation of [C₂H₃O]⁺ and [CH₃]⁺ ions originating from different parts of the parent ion was examined by means of ¹³C and deuterium labelling. Threshold-energy [H₂C?C(OH)? CH₃]^+˙ ions decompose to CH₃CO⁺+CH₃^˙ with appearance energy AE(CH₃CO⁺) = 11.03 ± 0.03 eV. Higher energy ions also form CH₂?C?OH⁺ + CH₃ with appearance energy AE(CH₂?C?OH⁺) = 12.2–12.3 eV. The fragmentation competes with hydrogen migration between C(1) and C(3) in the parent ion. [C₂H₃O]⁺ ions containing the original methyl group and [CH₃]⁺ ions incorporating the former methylene and the hydroxyl hydrogen atom are formed preferentially, compared with their corresponding counterparts. This behaviour is due to rate-determining isomerization [H₂C?C(OH)? CH₃]^+˙ →[CH₃COCH₃]^+˙, followed by asymmetrical fragmentation of the latter ions. Effects of internal energy and isotope substitution are discussed.     

Dioxygen Reactivity of Copper(I)/Manganese(II)-Porphyrin Assemblies: Mechanistic Studies and Cooperative Activation of O2

The oxidation of transition metals such as manganese and copper by dioxygen (O₂) is of great interest to chemists and biochemists for fundamental and practical reasons. In this report, the O₂ reactivities of 1:1 and 1:2 mixtures of [(TPP)Mn^II] (1; TPP: Tetraphenylporphyrin) and [(tmpa)Cu^I(MeCN)]⁺ (2; TMPA: Tris(2-pyridylmethyl)amine) in 2-methyltetrahydrofuran (MeTHF) are described. Variable-temperature (−110 °C to room temperature) absorption spectroscopic measurements support that, at low temperature, oxygenation of the (TPP)Mn/Cu mixtures leads to rapid formation of a cupric superoxo intermediate, [(tmpa)Cu^II(O₂^•–)]⁺ (3), independent of the presence of the manganese porphyrin complex (1). Complex 3 subsequently reacts with 1 to form a heterobinuclear μ-peroxo species, [(tmpa)Cu^II–(O₂^2–)–Mn^III(TPP)]⁺ (4; λ_max = 443 nm), which thermally converts to a μ-oxo complex, [(tmpa)Cu^II–O–Mn^III(TPP)]⁺ (5; λ_max = 434 and 466 nm), confirmed by electrospray ionization mass spectrometry and nuclear magnetic resonance spectroscopy. In the 1:2 (TPP)Mn/Cu mixture, 4 is subsequently attacked by a second equivalent of 3, giving a bis-μ-peroxo species, i.e., [(tmpa)Cu^II−(O₂²⁻)−Mn^IV(TPP)−(O₂²⁻)−Cu^II(tmpa)]²⁺ (7; λ_max = 420 nm and δ_pyrrolic = −44.90 ppm). The final decomposition product of the (TPP)Mn/Cu/O₂ chemistry in MeTHF is [(TPP)Mn^III(MeTHF)₂]⁺ (6), whose X-ray structure is also presented and compared to literature analogs.     

Thermodynamic Solution Properties of a Biodegradable Chelant (L-glutamic-N,N-diacetic Acid,L-GLDA) and Its Sequestering Ability toward Cd2+

The thermodynamics of the interaction of L-glutamic-N,N-diacetic acid (GLDA) with protons was studied potentiometrically at different temperatures, ionic strengths and ionic media. Four protonation constants and corresponding enthalpy changes occurred at infinite dilution together with temperature and ionic strength coefficients. The medium effect was also interpreted in terms of the formation of weak complexes between the ligand and the cations of supporting electrolytes, resulting in a greater tendency of GLDA to chemically interact with Na⁺ rather than K⁺ and, in turn, (CH₃)₄N⁺. Formation constants of GLDA with Cd²⁺ were determined in NaCl_(aq) at different ionic strength values. Five complex species were found, namely CdL²⁻, CdHL⁻, CdH₂L⁰_(aq), Cd₂L⁰_(aq), and Cd(OH)L³⁻, whose formation constant values at infinite dilution were log β = 12.68, 17.61, 20.76, 17.52, and 1.77, respectively. All the species results were relevant in the pH range of natural waters, although the Cd₂L⁰_(aq) was observed only for C_Cd ≥ C_GLDA and concentrations of >0.1 mmol dm⁻³. The sequestering ability of GLDA toward Cd²⁺, evaluated by means of pL_0.5, was maximum at pH~10, whereas the presence of a chloride containing a supporting electrolyte exerted a negative effect. Among new generation biodegradable ligands, GLDA was the most efficient in Cd²⁺ sequestration.     

Bifunctional activation of amine-boranes by the W/Pd bimetallic analogs of “frustrated Lewis pairs”

The reaction between basic [(PCP)Pd(H)] (PCP = 2,6-(CH₂P(t-C₄H₉)₂)₂C₆H₄) and acidic [LWH(CO)₃] (L = Cp (1a), Tp (1b); Cp = η⁵-cyclopentadienyl, Tp = κ³-hydridotris(pyrazolyl)borate) leads to the formation of bimolecular complexes [LW(CO)₂(μ-CO)⋯Pd(PCP)] (4a, 4b), which catalyze amine-borane (Me₂NHBH₃, ^tBuNH₂BH₃) dehydrogenation. The combination of variable-temperature (¹H, ³¹P{¹H}, ¹¹B NMR and IR) spectroscopies and computational (ωB97XD/def2-TZVP) studies reveal the formation of an η¹-borane complex [(PCP)Pd(Me₂NHBH₃)]⁺[LW(CO₃)]⁻ (5) in the first step, where a BH bond strongly binds palladium and an amine group is hydrogen-bonded to tungsten. The subsequent intracomplex proton transfer is the rate-determining step, followed by an almost barrierless hydride transfer. Bimetallic species 4 are easily regenerated through hydrogen evolution in the reaction between two hydrides.

Bimetallic complexes [LW(CO)₂(μ-CO)⋯Pd(PCP)] cooperatively activate amine-boranes for their dehydrogenation via N–H proton tunneling at RDS and H₂ evolution from two neutral hydrides.     

Reductive Methylation of Homogeneous Primary β-Lauryl/myristyl 7/3 Polyethyleneoxy n = 3–18 Ethylamines under Phase-Transfer Catalysis Conditions

Homogeneous tertiary N,N-dimethyl-N-β-lauryl/myristyl 7/3 polyethyleneoxy n = 3–18 ethylamines, LM(EO)_nAT, are niche intermediates in the synthesis of homogeneous N-alkyl (C₁–C₁₈)-N,N-dimethyl-N-β-lauryl/myristyl 7/3 polyethyleneoxy n = 3–18 ethylammonium chlorides (unitary degree of oligomerization of ethylene oxide in the polyoxyethylene chain). This paper synthetically presents the dependence of the reductive methylation yields of homogeneous primary β-lauryl/myristyl 7/3 polyethyleneoxy n = 3–18 ethylamines, LM(EO)_nAP, on the reaction time (10–90 min), the temperature (70 °C), the molar ratio formic aldehyde /LM(EO)_nAP (1.1/1–2.5/1), the molar ratio HCOOH/LM(EO)_nAP (5/1), the degree of oligomerization of ethylene oxide in the homogeneous polyoxyethylene chain in the 3,6,9,12,18 series, and the structure of the phase-transfer catalysts. The steric effects of hydrophobic groups CH₃ and C₁₈H₃₇ grafted onto the ammonium function, and the micellar phenomena in the vicinity of their critical micellar concentration, directly proportional to the homogeneous degree of oligomerization, were highlighted. In all cases, a steady increase in reductive methylation yields was observed, with even quantitative values obtained. The high purity of the homologous series LM(EO)_nAT will allow their personalization as reference structures for the study of the evolution of basic colloidal characteristics useful in forecasting technological applications. LM(EO)_nAP were obtained either by direct amidoethylation (nucleophilic addition under basic catalysis of homogeneous lauryl/myristyl 7/3 polyethoxylated n = 3, 6, 9, 12, 18 alcohols, LM(EO)_nOH, to acrylamide monomer) or by cyanoethylation of LM(EO)_nOH under basic catalysis at 25–50 °C, in the presence of Fe²⁺ cations as oligomerization/polymerization inhibitor, followed by partial acid hydrolysis of homogeneous β-alkyl (C₁₂H₂₅/C₁₄H₂₉) 7/3 polyethyleneoxy n = 3, 6, 9, 12, 18 propionitriles, LM(EO)_nPN, to β-alkyl (C₁₂H₂₅/C₁₄H₂₉) 7/3 polyethyleneoxy n = 3, 6, 9, 12, 18 propionamides, LM(EO)_nPD, which led to LM(EO)_nAP by Hoffmann degradation. Homogeneous higher tertiary polyetheramines LM(EO)_nAT were structurally characterized.     

Switching-On Fluorescence by Copper (II) and Basic Anions: A Case Study with a Pyrene-Functionalized Squaramide

The new symmetric acyclic N,N’-bis(1-pyrenyl) squaramide (H₂L) functionalized with the pyrene moiety as a fluorogenic fragment has been designed and its ability to selectively detect specific anions and metals investigated. H₂L selectively binds Cl⁻ both in solution (DMSO 0.5% H₂O and MeCN) and in the solid state, and allows to selectively detect Cu²⁺ in MeCN with the formation of a 2:1 metal-receptor complex, with a green intense emission appreciable by naked eye under the UV lamp. The H₂L copper complex preserves its emission properties in the presence of Cl⁻. The addition of basic anions (OH⁻, CN⁻, and F⁻) up to 10 equivalents caused the deprotonation of the squaramide NHs and a dramatic change of the emission properties of the H₂L copper complex.     

Thermodynamics Analysis and Removal of P in a P-(M)-H2O System

In order to efficiently remove phosphorus, thermodynamic equilibrium diagrams of the P-H₂O system and P-M-H₂O system (M stands for Fe, Al, Ca, Mg) were analyzed by software from Visual MINTEQ to identify the existence of phosphorus ions and metal ions as pH ranged from 1 to 14. The results showed that the phosphorus ions existed in the form of H₃PO₄, H₂PO₄⁻, HPO₄²⁻, and PO₄³⁻. Among them, H₂PO₄⁻ and HPO₄²⁻ were the main species in the acidic medium (99% at pH = 5) and alkaline medium (97.9% at pH = 10). In the P-Fe-H₂O system ((P) = 0.01 mol/L, (Fe³⁺) = 0.01 mol/L), H₂PO₄⁻ was transformed to FeHPO₄⁺ at pH = 0–7 due to the existence of Fe³⁺ and then transformed to HPO₄²⁻ at pH > 6 as the Fe³⁺ was mostly precipitated. In the P-Ca-H₂O system ((P) = 0.01 mol/L, (Ca²⁺) = 0.015 mol/L), the main species in the acidic medium was CaH₂PO₄⁺ and HPO₄²⁻, and then transformed to CaPO₄⁻ at pH > 7. In the P-Mg-H₂O system ((P) = 0.01 mol/L, (Mg²⁺) = 0.015 mol/L), the main species in the acidic medium was H₂PO₄⁻ and then transformed to MgHPO₄ at pH = 5–10, and finally transformed to MgPO₄⁻ as pH increased. The verification experiments (precipitation experiments) with single metal ions confirmed that the theoretical analysis could be used to guide the actual experiments.     

Identification of Molecules from Coffee Silverskin That Suppresses Myostatin Activity and Improves Muscle Mass and Strength in Mice

Coffee has been shown to attenuate sarcopenia, the age-associated muscle atrophy. Myostatin (MSTN), a member of the TGF-β growth/differentiation factor superfamily, is a potent negative regulator of skeletal muscle mass, and MSTN-inhibition increases muscle mass or prevents muscle atrophy. This study, thus, investigated the presence of MSTN-inhibitory capacity in coffee extracts. The ethanol-extract of coffee silverskin (CSE) but not other extracts demonstrated anti-MSTN activity in a pGL3-(CAGA)₁₂-luciferase reporter gene assay. CSE also blocked Smad3 phosphorylation induced by MSTN but not by GDF11 or Activin A in Western blot analysis, demonstrating its capacity to block the binding of MSTN to its receptor. Oral administration of CSE significantly increased forelimb muscle mass and grip strength in mice. Using solvent partitioning, solid-phase chromatography, and reverse-phase HPLC, two peaks having MSTN-inhibitory capacity were purified from CSE. The two peaks were identified as ^βN-arachinoyl−5-hydroxytryptamide (C₂₀−5HT) and ^βN-behenoyl−5-hydroxytryptamide (C₂₂−5HT) using mass spectrometry and NMR analysis. In summary, the results show that CSE has the MSTN-inhibitory capacity, and C₂₀−5HT and C₂₂−5HT are active components of CSE-suppressing MSTN activity, suggesting the potential of CSE, C₂₀−5HT, and C₂₂−5HT being developed as agents to combat muscle atrophy and metabolic syndrome.     

In silico design to enhance the barrier height for magnetization reversal in Dy(iii) sandwich complexes by stitching them under the umbrella of corannulene

Lanthanide based single molecular magnets (SMMs), particularly dysprocenium based SIMs, are well known for their high energy barrier for spin reversal (U_eff) and blocking temperatures (T_B). Enhancing these two parameters and at the same time obtaining ambient stability is key to realising end-user applications such as compact storage or as qubits in quantum computing. In this work, by employing an array of theoretical tools (DFT, ab initio CASSCF and molecular dynamics), we have modelled six complexes [(η⁵-corannulene)Dy(Cp)] (1), [(η⁵-corannulene)Dy(C₆H₆)] (2), [(η⁶-corannulene)Dy(Cp)] (3), [(η⁶-corannulene)Dy(C₆H₆)] (4), [(exo-η⁵-corannulene)Dy(endo-η⁵-corannulene)] (5), and [(endo-η⁵-corannulene)Dy(endo-η⁵-corannulene)] (6) containing corannulene as a capping ligand to stabilise Dy(iii) half-sandwich complexes. Our calculations predict a strong axiality exerted by the Dy–C interactions in all complexes. Ab initio calculations predict a very large barrier height for all six molecules in the order 1 (919 cm⁻¹) ≈ 3 (913 cm⁻¹) > 2 (847 cm⁻¹) > 4 (608 cm⁻¹) ≈ 5 (603 cm⁻¹) ≈ 6 (599 cm⁻¹), suggesting larger barrier heights for Cp ring systems, followed by six-membered arene systems and then corannulene. DFT based molecular dynamics calculations were performed on complexes 3, 5 and 6. For complexes 3 and 5, the geometries that are dynamically accessible are far fewer. The range of U_eff computed for molecular dynamics snapshots is high, indicating a possibility of translating the large U_eff obtained into attractive blocking temperatures in these complexes, but the converse is found for 6. Furthermore, an in-depth C–H bond vibrational analysis performed on complex 3 suggests that the vibration responsible for reducing the blocking temperature in dysprocenium SIMs is absent here as the C–H bonds are stronger and corannulene steric strain prevents the C(Cp)–Dy–C(Cor) bending. As [(η⁶-corannulene)TM(X)]⁺ (TM = Ru, Zr, Os, Rh, Ir and X = C₅Me₅, C₆Me₆) are known, the predictions made here have a higher prospect of yielding stability under ambient conditions, a very large U_eff value and a high blocking temperature – a life-giving combination to new generation SMMs.

Bringing half-sandwich Dy(iii) SIMs under the umbrella of corannulene was found to offer stability, greater barrier height and may offer higher blocking temperatures.     

Mechanistic Origin of Antagonist Effects of Usual Anionic Bases (OH−, CO32−) as Modulated by their Countercations (Na+, Cs+, K+) in Palladium‐Catalyzed Suzuki–Miyaura Reactions

The mechanism of the reaction of trans‐ArPdBrL₂ (Ar=p‐Z‐C₆H₄, Z=CN, H; L=PPh₃) with Ar′B(OH)₂ (Ar′=p‐Z′‐C₆H₄, Z′=H, CN, MeO), which is a key step in the Suzuki–Miyaura process, has been established in N,N‐dimethylformamide (DMF) with two bases, acetate (nBu₄NOAc) or carbonate (Cs₂CO₃) and compared with that of hydroxide (nBu₄NOH), reported in our previous work. As anionic bases are inevitably introduced with a countercation M⁺ (e.g., M⁺OH^?), the role of cations in the transmetalation/reductive elimination has been first investigated. Cations M⁺ (Na⁺, Cs⁺, K⁺) are not innocent since they induce an unexpected decelerating effect in the transmetalation via their complexation to the OH ligand in the reactive ArPd(OH)L₂, partly inhibiting its transmetalation with Ar′B(OH)₂. A decreasing reactivity order is observed when M⁺ is associated with OH^?: nBu₄N⁺> K⁺> Cs⁺> Na⁺. Acetates lead to the formation of trans‐ArPd(OAc)L₂, which does not undergo transmetalation with Ar′B(OH)₂. This explains why acetates are not used as bases in Suzuki–Miyaura reactions that involve Ar′B(OH)₂. Carbonates (Cs₂CO₃) give rise to slower reactions than those performed from nBu₄NOH at the same concentration, even if the reactions are accelerated in the presence of water due to the generation of OH^?. The mechanism of the reaction with carbonates is then similar to that established for nBu₄NOH, involving ArPd(OH)L₂ in the transmetalation with Ar′B(OH)₂. Due to the low concentration of OH^? generated from CO₃^2? in water, both transmetalation and reductive elimination result slower than those performed from nBu₄NOH at equal concentrations as Cs₂CO₃. Therefore, the overall reactivity is finely tuned by the concentration of the common base OH^? and the ratio [OH^?]/[Ar′B(OH)₂]. Hence, the anionic base (pure OH^? or OH^? generated from CO₃^2?) associated with its countercation (Na⁺, Cs⁺, K⁺) plays four antagonist kinetic roles: acceleration of the transmetalation by formation of the reactive ArPd(OH)L₂, acceleration of the reductive elimination, deceleration of the transmetalation by formation of unreactive Ar′B(OH)₃^? and by complexation of ArPd(OH)L₂ by M⁺.     

Nitric oxide monooxygenation (NOM) reaction of cobalt-nitrosyl {Co(NO)}8 to CoII-nitrito {CoII(NO2−)}: base induced hydrogen gas (H2) evolution

Here, we report the nitric oxide monooxygenation (NOM) reactions of a Co^III-nitrosyl complex (1, {Co-NO}⁸) in the presence of mono-oxygen reactive species, i.e., a base (OH⁻, tetrabutylammonium hydroxide (TBAOH) or NaOH/15-crown-5), an oxide (O²⁻ or Na₂O/15-crown-5) and water (H₂O). The reaction of 1 with OH⁻ produces a Co^II-nitrito complex {3, (Co^II-NO₂⁻)} and hydrogen gas (H₂), via the formation of a putative N-bound Co-nitrous acid intermediate (2, {Co-NOOH}⁺). The homolytic cleavage of the O–H bond of proposed [Co-NOOH]⁺ releases H₂via a presumed Co^III-H intermediate. In another reaction, 1 generates Co^II-NO₂⁻ when reacted with O²⁻via an expected Co^I-nitro (4) intermediate. However, complex 1 is found to be unreactive towards H₂O. Mechanistic investigations using ¹⁵N-labeled-¹⁵NO and ²H-labeled-NaO²H (NaOD) evidently revealed that the N-atom in Co^II-NO₂⁻ and the H-atom in H₂ gas are derived from the nitrosyl ligand and OH⁻ moiety, respectively.

Base-induced hydrogen (H₂) gas evolution in the nitric oxide monoxygenation reaction.

As a radical species, nitric oxide (NO) has attracted great interest from the scientific community due to its major role in various physiological processes such as neurotransmission, vascular regulation, platelet disaggregation and immune responses to multiple infections.¹ Nitric oxide synthase (NOS),² and nitrite reductase (NiR)³ enzymes are involved in the biosynthesis of NO. NOSs produce NO by the oxidation of the guanidine nitrogen in l-arginine.⁴ However, in mammals and bacteria, NO₂⁻ is reduced to NO by NiRs in the presence of protons, i.e., NO₂⁻ + e⁻ + 2H⁺ → NO + H₂O.⁵ Biological dysfunctions may cause overproduction of NO, and being radical it leads to the generation of reactive nitrogen species (RNS), i.e., peroxynitrite (PN, OONO⁻)⁶ and nitrogen dioxide (˙NO₂),⁷ upon reaction with reactive oxygen species (ROS) such as superoxide (O₂˙⁻),⁸ peroxide (H₂O₂),⁹ and dioxygen (O₂).¹⁰ Hence, it is essential to maintain an optimal level of NO. In this regard, nitric oxide dioxygenases (NODs)¹¹ are available in bio-systems to convert excess NO to biologically benign nitrate (NO₃⁻).¹²NO₂⁻ + Fe^II + H⁺ ↔ NO + Fe^III + OH⁻1[M–NO]ⁿ + 2OH⁻ → [M–NO₂]⁽ⁿ⁻²⁾ + H₂O2NOD enzymes generate NO₃⁻ from NO;^11b,12−13 however, the formation of NO₂⁻ from NO is still under investigation. Clarkson and Bosolo reported NO₂⁻ formation in the reaction of Co^III-NO and O₂.¹⁴ Nam and co-workers showed the generation of Co^II-NO₂⁻ from Co^III-NO upon reaction with O₂˙⁻.¹⁵ Recently, Mondal and co-workers reported NO₂⁻ formation in the reaction of Co^II-NO with O₂.¹⁶ Apart from cobalt, the formation of Cu^II-NO₂⁻ was also observed in the reaction of Cu^I-NO and O₂.¹⁷ For metal-dioxygen adducts, i.e., Cr^III-O₂˙⁻ and Mn^IV-O₂²⁻, NOD reactions led to the generation of Cr^III-NO₂⁻ (ref. 18) and Mn^V O + NO₂⁻,¹⁹ respectively. However, the NOD reaction of Fe^III-O₂˙⁻ and Fe^III-O₂²⁻ with NO and NO⁺, respectively, generated Fe^III-NO₃⁻via Fe^IV O and ˙NO₂.²⁰ Ford suggested that the reaction of ferric-heme nitrosyl with hydroxide leads to the formation of NO₂⁻ and H⁺.¹² Lehnert and co-workers reported heme-based Fe-nitrosyl complexes²¹ showing different chemistries due to the Fe^II-NO⁺ type electronic structures. On the other hand, Bryan proposed that the one-electron reduction of NO₂⁻ to NO in ferrous heme protein is reversible (eqn (1)).²² Also, it is proposed that excess NO in biological systems is converted to NO₂⁻ and produces one equivalent of H⁺ upon reaction with ˙OH.²³ Previously reported reactivity of M–NOs of Fe²⁴ with OH⁻ suggested the formation of NO₂⁻ and one equivalent of H⁺, where H⁺ further reacts with one equivalent of OH⁻ and produces H₂O (eqn (2)).²⁵Here in this report, we explore the mechanistic aspects of nitric oxide monooxygenation (NOM) reactions of the Co^III-nitrosyl complex, [(12TMC)Co^III(NO⁻)]²⁺/{Co(NO)}⁸ (1),^15,26 bearing the 12TMC ligand (12TMC = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) with mono-oxygen reactive species (O²⁻, OH⁻ and H₂O) (Scheme 1). Complex 1 reacts with the base (OH⁻, tetrabutylammonium hydroxide (TBAOH)/or NaOH in the presence of 15-crown-5 as the OH⁻ source) and generates the corresponding Co^II-nitrito complex, [(12TMC)Co^II(NO₂⁻)]⁺ (3), with the evolution of hydrogen gas (H₂) via the formation of a plausible N-bound Co-nitrous acid intermediate ([Co-NOOH]⁺, 2) in CH₃CN at 273 K (Scheme 1, reaction (I)). Also, when 1 reacts with the oxide (O²⁻ or Na₂O in the presence of 15-crown-5), it generates the Co^II-nitrito complex (3) via a probable Co^I-nitro, [(12TMC)Co^I(NO₂⁻)] (4), intermediate (Scheme 1, reaction (II)); however, 1 does not react with water (Scheme 1, reaction (III)). Mechanistic investigations using ¹⁵N-labeled-¹⁵NO, D-labeled-NaOD and ¹⁸O-labelled-¹⁸OH⁻ demonstrated, unambiguously, that the N and O-atoms in the NO₂⁻ ligand of 3 resulted from NO and OH⁻ moieties; however, the H-atoms of H₂ are derived from OH⁻. To the extent of our knowledge, the present work reports the very first systematic study of Co^III-nitrosyl complex reactions with H₂O, OH⁻ and O²⁻. This new finding presents an alternative route for NO₂⁻ generation in biosystems, and also illustrates a new pathway of H₂ evolution, in addition to the reported literature.^12,27Open in a separate windowScheme 1Nitric oxide monooxygenation (NOM) reactions of cobalt-nitrosyl complex (1) in the presence of a base (OH⁻), sodium oxide (Na₂O) and water (H₂O).To further explore the chemistry of [(12TMC)Co^III(NO⁻)]²⁺ (1),^15,26 and the mechanistic insights of NOM reactions, we have reacted it with a base (OH⁻), an oxide (O²⁻), and water (H₂O). When complex 1 was reacted with TBAOH in CH₃CN, the color of complex 1 changed to light pink from dark pink. In this reaction, the characteristic absorption band of 1 (370 nm) disappears within 2 minutes (Fig. 1a; ESI, Experimental section (ES) and Fig. S1a^†), producing a Co^II-nitrito complex, [(12TMC)Co^II(NO₂⁻)]⁺ (3), with H₂ (Scheme 1, reaction (Ib)), in contrast to the previous reports on base induced NOM reactions (eqn (2)).^12,25,28 The spectral titration data confirmed that the ratio-metric equivalent of OH⁻ to 1 was 1 : 1 (ESI, Fig. S1b^†). 3 was determined to be [(12TMC)Co^II(NO₂⁻)](BF₄) based on various spectroscopic and structural characterization experiments (vide infra).^15,26bOpen in a separate windowFig. 1(a) UV-vis spectral changes of 1 (0.50 mM, black line) upon addition of OH⁻ (1 equiv.) in CH₃CN under Ar at 273 K. Black line (1) changed to red line (3) upon addition of OH⁻. Inset: IR spectra of 3-¹⁴NO₂⁻ (blue line) and 3-¹⁵NO₂⁻ (red line) in KBr. (b) ESI-MS spectra of 3. The peak at 333.2 is assigned to [(12TMC)Co^II(NO₂)]⁺ (calcd m/z 333.1). Inset: isotopic distribution pattern for 3-¹⁴NO₂⁻ (red line) and 3-¹⁵NO₂⁻ (blue line).The FT-IR spectrum of 3 showed a characteristic peak for nitrite stretching at 1271 cm⁻¹ (Co^II-14NO₂⁻) and shifted to 1245 cm⁻¹ (Co^II-15NO₂⁻) when 3 was prepared by reacting ¹⁵N-labeled NO (Co^III-15NO) with OH⁻ (Inset, Fig. 1a and Fig. S2^†). The shifting of NO₂⁻ stretching (Δ = 30 cm⁻¹) indicates that the N-atom in the NO₂⁻ ligand is derived from Co^III-15NO. The ESI-MS spectrum of 3 showed a prominent peak at m/z 333.2, [(12TMC)Co^II(¹⁴NO₂⁻)]⁺ (calcd m/z 333.2), which shifted to 334.2, [(12TMC)Co^II(¹⁵NO₂⁻)]⁺ (calcd m/z 334.2), when the reaction was performed with Co^III-15NO (Inset, Fig. 1b; ESI, Fig. S3a^†); indicating clearly that NO₂⁻ in 3 was derived from the NO moiety of 1. In addition, we have reacted 1 with Na¹⁸OH (ES and ESI^†), in order to follow the source of the second O-atom in 3-NO₂⁻. The ESI-MS spectrum of the reaction mixture, obtained by reacting 1 with Na¹⁸OH, showed a prominent peak at m/z 335.2, [(12TMC)Co^II(¹⁸ONO⁻)]⁺ (calcd m/z 335.2), (SI, Fig. S3b^†) indicating clearly that NO₂⁻ in 3 was derived from ¹⁸OH⁻. The ¹H NMR spectrum of 3 did not show any signal for aliphatic protons of the 12TMC ligand, suggesting a bivalent cobalt center (Fig. S4^†).^26b Furthermore, we have determined the magnetic moment of 3, using Evans'' method, and it was found to be 4.62 BM, suggesting a high spin Co(ii) metal center with three unpaired electrons (ESI^† and ES).²⁹ The exact conformation of 3 was provided by single-crystal X-ray crystallographic analysis (Fig. 2b, ESI, ES, Fig. S5, and Tables T1 and T2^†) and similar to that of previously reported Co^II-NO₂⁻/M^II-NO₂⁻.^15,26b Also, we have quantified the amount of nitrite (90 ± 5%), formed in the above reaction, using the Griess reagent (ESI, ES, and Fig. S6^†).Open in a separate windowFig. 2Displacement ellipsoid plot (20% probability) of 3 at 100 K. Disordered C-atoms of the TMC ring, anion and H-atoms have been removed for clarity.As is known from the literature, a metal-nitrous acid intermediate may form either by the reaction of a metal-nitrosyl with a base²⁷ or by the metal-nitrite reaction with an acid (nitrite reduction chemistry);^26b however, the products of both the reactions are different. Here, for the first time, we have explored the reaction of Co^III-nitrosyl (1) with a base. In this reaction, it is clear that the formation of Co^II-nitrito would be accomplished by the release of H₂ gas via the generation of a transient N-bound [Co-(NOOH)]⁺ intermediate (Scheme 2, reaction (II)). The formation of Co^II-NO₂⁻ (3) from the [Co-(NOOH)]⁺ intermediate is likely to proceed by either (i) homolytic cleavage of the O–H bond and release of H₂via the proposed Co^III-H transient species (Co^III-H = Co^II + 1/2H₂)³⁰ (Scheme 2, reaction (III)), as reported in previous literature where the reduced cobalt, in a number of different ligand environments, is a good H⁺ reduction catalyst and generates H₂ gas via a Co^III-H intermediate³¹ or (ii) heterolytic cleavage of the O–H bond and the formation of Co^I-NO₂⁻ + H⁺.²⁷ In the present study, we observed the formation of 3 and H₂via the plausible homolytic cleavage of the NOO–H moiety of 2 as shown in Scheme 2, in contrast to the previous reports on base-induced reactions on metal-nitrosyls (eqn (3)).²⁷ Taking together both possibilities, (i) is the most reasonable pathway for the NOM reaction of complex 1 in the presence of a base (as shown in Scheme 2, reaction (III)). And the reaction is believed to go through a Co^III-H intermediate as reported previously in Co^I-induced H⁺ reduction in different ligand frameworks and based on literature precedence, we believe that complex 1 acts in a similar manner.³¹Open in a separate windowScheme 2NOM reaction of complex 1 in the presence of OH⁻, showing the generation of Co^II-nitrito (3) and H₂via a Co(iii)-hydrido intermediate.In contrast to an O-bound Co^II-ONOH intermediate, where N–O bond homolysis of the ON-OH moiety generates H₂O₂ (Scheme 2, reaction (IV)),^26b the N-bound [Co-(NOOH)]⁺ intermediate decomposes to form NO₂⁻ and a Co(iii)-H transient species, arising from β-hydrogen transfer from the NOO–H moiety to the cobalt-center (Scheme 2, reaction (II)).^30a,c,32 The Co(iii)-hydrido species may generate H₂ gas either (a) by its transformation to the Co(ii)-nitrito complex (2) and H₂ gas as observed in the case of Co^III-H intermediate chemistry^30a,c,e−g as proposed in the chemistry of the Co^I complex with H⁺ reduction³¹ and other metal-hydrido intermediates³² and also explained in O₂ formation in PN chemistry^17,33 or (b) by the reacting with another [Co-(NOOH)]⁺ intermediate (Scheme 2, reaction (III)).Furthermore, we have confirmed the H₂ formation in the NOM reaction of 1 with OH⁻ by headspace gas mass spectrometry (Fig. 3a). Also, carrying out the reaction of 1 with NaOD leads to the formation of the [Co-(NOOD)]⁺ intermediate, which then transforms to a Co^III-D transient species. Further, as described above, the Co^III-D species releases D₂ gas, detected by headspace gas mass spectrometry (Fig. 3b), which evidently established that H₂ gas formed in the reaction of 1 with OH⁻. In this regard, we have proposed that in the first step of this reaction, the nucleophilic addition of OH⁻ to {Co-NO}⁸ generates a transient N-bound [Co-(NOOH)]⁺ intermediate that is generated by an internal electron transfer to Co^III (Scheme 2, reaction (I)). By following the mechanism proposed in the case of Co^III-H,^30a−c O₂,¹⁵ and H₂O₂(ref. 26b) formation, we have proposed the sequences of the NOM reaction of 1, which leads to the generation of Co^II-nitrito and H₂ (Scheme 2, reaction (I)–(III) and Scheme 3). In the second step, O–H bond homolytic cleavage generates a Co^III-H transient species + NO₂⁻via a β-hydrogen elimination reaction of the [Co-(NOOH)]⁺ intermediate.³² The Co^III-H intermediate may undergo the following reactions to generate H₂ gas and Co^II-nitrito either (a) by the natural decomposition of the Co^III-H transient species to generate H₂,^30a,c,e−g or (b) by the H-atom abstraction from another [Co-(NOOH)]⁺ intermediate (Scheme 3). Also, to validate our assumption that the reaction goes through a plausible N-bound [Co-(NOOH)]⁺ intermediate followed by its transformation to the Co^III-H species (vide supra), we have performed the reaction of 1 with NaOH/NaOD (in 1 : 1 ratio). In this reaction, we have observed the formation of a mixture of H₂, D₂, and HD gases, which indicates clearly that the reaction goes through the formation of Co^III-H and Co^III-D transient species via the aforementioned mechanism (Fig. 3c). This is the only example where tracking of the H atoms has confirmed the H₂ generation from an N-bound NOO–H moiety as proposed for H₂ formation from Co^III-H.³⁰Open in a separate windowFig. 3Mass spectra of formation of (a) H₂ in the reaction of 1 (5.0 mM) with NaOH (5.0 mM), (b) D₂ in the reaction of 1 (5.0 mM) with NaOD (5.0 mM), (c) D₂, HD, and H₂ in the reaction of 1 (5.0 mM) with NaOD/NaOH (1 : 1), and (d) H₂ in the reaction of 1 (5.0 mM) with NaOH in the presence of 2,4 DTBP (50 mM).Open in a separate windowScheme 3NOM reaction of complex 1 in the presence of OH⁻, showing the different steps of the reaction.While, we do not have direct spectral evidence to support the formation of the transient N-bound [Co-(NOOH)]⁺ intermediate and its decomposition to the Co^III-H transient species via β-hydrogen transfer from the NOOH moiety to the cobalt center, support for its formation comes from our finding that the reactive hydrogen species can be trapped by using 2,4-di-tert-butyl-phenol (2,4-DTBP).³⁴ In this reaction, we observed the formation of 2,4-DTBP-dimer (2,4-DTBP-D, ∼67%) as a single product (ESI, ES, and Fig. S7^†). This result can readily be explained by the H-atom abstraction reaction of 2,4-DTBP either by [Co-(NOOH)]⁺ or Co^III-H, hence generating a phenoxyl-radical and 3 with H₂ (Fig. 3d and Scheme 2, reaction (a)). Also, we have detected H₂ gas formation in this reaction (ESI,^† ES, and Fig. 3d). In the next step, two phenoxyl radicals dimerized to give 2,4-DTBP-dimer (Scheme 2c, reaction (II)). Thus, the observation of 2,4-DTBP-dimer in good yield supports the proposed reaction mechanism (Scheme 2, reaction (a) and (b)). Further, the formation of 2,4 DTBP as a single product also rules out the formation of the hydroxyl radical as observed in the case of an O-bound nitrous acid intermediate.^26bFurthermore, we have explored the NOM reactivity of 1 with Na₂O/15-crown-5 (as the O²⁻ source) and observed the formation of the Co^II-nitrito complex (3) via a plausible Co^I-nitro (4) intermediate (Scheme 1, reaction (IIa); also see the ESI^† and ES); however, 1 was found to be inert towards H₂O (Scheme 1, reaction (III); also see the ESI, ES and Fig. S8^†). The product obtained in the reaction of 1 with O²⁻ was characterized by various spectroscopic measurements.^15,26b The UV-vis absorption band of 1 (λ_max = 370 nm) disappears upon the addition of 1 equiv. of Na₂O and a new band (λ_max = 535 nm) forms, which corresponds to 3 (ESI, Fig. S9^†). The FT-IR spectrum of the isolated product of the above reaction shows a characteristic peak for Co^II-bound nitrite at 1271 cm⁻¹, which shifts to 1245 cm⁻¹ when exchanged with ¹⁵N-labeled-NO (¹⁵N¹⁶O) (ESI, ES, and Fig. S10^†), clearly indicating the generation of nitrite from the NO ligand of complex 1.^26b The ESI-MS spectrum recorded for the isolated product (vide supra) shows a prominent ion peak at m/z 333.1, and its mass and isotope distribution pattern matches with [(12-TMC)Co^II(NO₂)]⁺ (calc. m/z 333.1) (ESI, Fig. S11^†). Also, we quantified the amount of 3 (85 ± 5%) by quantifying the amount of nitrite (85 ± 5%) using the Griess reagent test (ESI, ES, and Fig. S6^†).In summary, we have demonstrated the reaction of Co^III-nitrosyl, [(12-TMC)Co^III(NO⁻)]²⁺/{CoNO}⁸ (1), with mono-oxygen reactive species (O²⁻, OH⁻ and H₂O) (Scheme 1). For the first time, we have established the clear formation of a Co^II-nitrito complex, [(12TMC)Co^II(NO₂⁻)]⁺ (3), and H₂ in the reaction of 1 with one equivalent of OH⁻via a transient N-bound [Co-(NOOH)]⁺ (2) intermediate. This [Co-(NOOH)]⁺ intermediate undergoes the O–H bond homolytic cleavage and generates a Co^III-H transient species with NO₂⁻, via a β-hydrogen elimination reaction of the [Co-(NOOH)]⁺ intermediate, which upon decomposition produces H₂ gas. This is in contrast to our previous report, where acid-induced nitrite reduction of 3 generated 1 and H₂O₂via an O-bound Co^II-ONOH intermediate.^26b Complex 1 was found to be inert towards H₂O; however, we have observed the formation of 3 when reacted with O²⁻. It is important to note that H₂ formation involves a distinctive pathway of O–H bond homolytic cleavage in the [Co-(NOOH)]⁺ intermediate, followed by the generation of the proposed Co^III-H transient species (Co^II + 1/2H₂)³⁰ prior to H₂ evolution as described in Co^I chemistry with H⁺ in many different ligand frameworks.³¹ The present study is the first-ever report where the base induced NOM reaction of Co^III-nitrosyl (1) leads to Co^II-nitrito (3) with H₂ evolution via an N-bound [Co-(NOOH)]⁺ intermediate, in contrast to the chemistry of O-bound Co^II-ONOH^26b, hence adding an entirely new mechanistic insight of base induced H₂ gas evolution and an additional pathway for NOM reactions.