Reactivity Of Complexes Research Articles

Mitochondrial reactive oxygen species-mediated fibroblast activation has a role in tumor microenvironment formation in radiation carcinogenesis.

Cancer risks attributable to low-dose and low-dose-rate radiation are a serious concern for public health. Radiation risk assessment is based on lifespan studies among Hiroshima-Nagasaki A-bomb survivors; however, there are statistical limitations due to a small sample size for low-dose radiation. Therefore, basic biological studies are helpful in understanding the mechanism of radiation carcinogenesis. The detrimental effects of ionising radiation (IR) are caused by reactive oxygen species (ROS)-mediated oxidative DNA damage. IR-induced delayed ROS are produced in the electron transport chain reaction of the mitochondrial complex. Thus, mitochondria are a source of ROS and a primary target for ROS attacks. Consequently, mitochondrial dysfunction is thought to be a key event in the metabolic changes of cancer cells and is important in radiation-induced carcinogenesis. In this paper, we present recent findings on radiation carcinogenesis effect assessment, focusing on mitochondrial function as stress sensors.

Trinuclear Lutetium(III) Cyclopentadienyl Complex with the 2,2´-Bipyridine Dianion

The reaction of lutetium cyclopentadienyl anthracenide complex (C5H5)Lu(C14H10)(THF)2] with 1 equiv. of 2,2´-bipyridine in THF gives the trinuclear complex [{(η5-C5H5)Lu}3(μ₂-Bipy)₃] (I), containing a 2,2´-bipyridine dianion. The complex was isolated as a powder with the composition I·0.1(C14H10)·0.8(C7H8). The recrystallization from a toluene/hexane mixture resulted in the crystals of I·0.084(C14H10)·0.831(C7H8)· · 0.500(C6H14), which were studied by X-ray diffraction (monoclinic group P21/c; CCDC no. 2311508). Complex I has an unusual μ2-κ2N1,N1´:η4N1,C2,C2´,N1´-bridging coordination of the dianion.

Basicity of MnIII-Hydroxo Complexes Controls the Thermodynamics of Proton-Coupled Electron Transfer Reactions.

Several manganese-dependent enzymes utilize MnIII-hydroxo units in concerted proton-electron transfer (CPET) reactions. We recently demonstrated that hydrogen bonding to the hydroxo ligand in the synthetic [MnIII(OH)(PaPy2N)]+ complex increased rates of CPET reactions compared to the [MnIII(OH)(PaPy2Q)]+ complex that lacks a hydrogen bond. In this work, we determine the effect of hydrogen bonding on the basicity of the hydroxo ligand and evaluate the corresponding effect on CPET reactions. Both [MnIII(OH)(PaPy2Q)]+ and [MnIII(OH)(PaPy2N)]+ react with strong acids to yield MnIII-aqua complexes [MnIII(OH2)(PaPy2Q)]2+ and [MnIII(OH2)(PaPy2N)]2+, for which we determined pKa values of 7.6 and 13.1, respectively. Reactions of the MnIII-aqua complexes with one-electron reductants yielded estimates of reduction potentials, which were combined with pKa values to give O-H bond dissociation free energies (BDFEs) of 77 and 85 kcal mol-1 for the MnII-aqua complexes [MnII(OH2)(PaPy2Q)]+ and [MnII(OH2)(PaPy2N)]+. Using these BDFEs, we performed an analysis of the thermodynamic driving force for phenol oxidation by these complexes and observed the unexpected result that slower rates are associated with more asynchronous CPET. In addition, reactions of acidic phenols with the MnIII-hydroxo complexes show rates that deviate from the thermodynamic trends, consistent with a change in mechanism from CPET to proton transfer.

Ceric Ammonium Nitrate Oxidation of a MnII Complex Generates a Bis(μ-oxo)dimanganese(IV,IV) Product via a MnIV-Oxo Intermediate.

The oxidation of manganese complexes using ceric ammonium nitrate (CAN) is often complicated by the fact that cerium(IV) can serve as both an oxidant and a Lewis acid. In this work, we explore the reaction of CAN with the MnII complex [MnII(OTf)(DMMN4py)](OTf) (DMMN4py = N,N-bis(4-methoxy-3,5-dimethyl-2-pyridylmethyl)-N-bis(2-pyridyl)methylamine). We chose this complex as multiple oxidation products, including oxomanganese(IV) and bis(μ-oxo)dimanganese(III,IV) complexes, have previously been reported. We envisioned that knowledge of the spectral properties of these intermediates would aid in understanding the potential complexities of CAN oxidation reactions. The oxidation of [MnII(OTf)(DMMN4py)](OTf) with 2.0 equiv CAN in 9:1 (v/v) MeCN:H2O at 25 °C transiently forms the MnIV-oxo complex, but this species is formed in low yields and is unstable. The MnIV-oxo complex evolves to a new intermediate that had not been previously observed. At lower temperatures, the formation of this new intermediate is preceded by formation of the previously reported bis(μ-oxo)dimanganese(III,IV) complex. EPR and X-ray absorption experiments for the new intermediate provide strong evidence for its formulation as [MnIVMnIV(μ-O)2(DMMN4py)2]4+. This work establishes dinuclear MnIVMnIV species as products that must be considered in CAN oxidation reactions of MnII complexes and shows that both mononuclear MnIV-oxo and dinuclear MnIIIMnIV complexes can be intermediates in such reactions.

Half-Sandwich Cerium and Lanthanum Dialkyl Complexes: Synthesis, Structure, and Reactivity Studies.

Cerium and lanthanum dialkyl complexes [η5-1,2,4-(Me3C)3C5H2]Ln(CH2C6H4-o-NMe2)2 (Ln = Ce 1 and La 2), supported by a tri-tert-butylcyclopentadienyl ligand, have been successfully synthesized. Studies demonstrate that these complexes possess diverse reactivity toward various small molecules. For example, the reaction of complexes 1 and 2 with diphenyl dichalcogenides PhEEPh (E = S, Se) results in the formation of lanthanide thiolates [(η5-1,2,4-(Me3C)3C5H2)Ln(SPh)(μ-SPh)]2 (Ln = Ce 3 and La 4) and selenolates [(η5-1,2,4-(Me3C)3C5H2)Ln(SePh)(μ-SePh)]2 (Ln = Ce 5 and La 6), concomitantly releasing PhE(CH2C6H4-o-NMe2). Furthermore, complexes 1 and 2, upon reaction with dibenzyl disulfide, yield tetranuclear rare-earth metallomacrocyclic compounds {[(η5-1,2,4-(Me3C)3C5H2)Ln(μ-SCH2C6H5)]2(μ-η3:η3-SCHC6H5)}2 (Ln = Ce 7 and La 8). This reaction may involve a process of σ-bond metathesis and C-H activation. While the reaction of 1 and 2 with dibenzyl diselenide in the presence of LiCH2C6H4-o-NMe2 leads to the formation of lanthanide-lithium selenido clusters [(η5-1,2,4-(Me3C)3C5H2)La(μ-SeCH2C6H5)]3(μ3-Se)[μ3-SeLi(THF)3] (Ln = Ce 9 and La 10). Meanwhile, lanthanide selenido clusters [(η5-1,2,4-(Me3C)3C5H2)La(μ-SeCH2C6H4-o-NMe2)]4(μ3-Se)2 (Ln = Ce 11 and La 12) can be obtained by treating 1 and 2 with elemental selenium in a 1:2 molar ratio. Additionally, the treatment of 1 and 2 with benzoxazole generates ring-opening/C-C coupling/C-N coupling products {(η5-1,2,4-(Me3C)3C5H2)La[μ-OC6H4-o-N═CHN(CH(CH2C6H4-o-NMe2)2C6H4-o-O]}2 (Ln = Ce 13 and La 14). All new compounds were characterized by various spectroscopic methods, and their solid-state structures were confirmed by single-crystal X-ray diffraction analyses.

Formation of Radical-like NH Ligand from NH3 at Ambient Conditions Mediated by Dialkyl Rare-Earth Complexes.

Although intensive work on ammonia activation has been carried out in recent decades, generating nitrogen-centered radicals from NH3 under ambient conditions remains quite challenging. In the presented research, the conversion of NH3 to radical-like NH ligand has been achieved by the reactions of a series of dialkyl rare-earth (RE) complexes (1-RE, RE = Tb, Dy, Y, Ho, Er, Yb, and Lu) supported by β-diketiminate ligands with NH3 in n-hexane at room temperature, resulting in the formations of the radical-like μ3-NH ligands containing trinuclear RE complexes (2-RE). The radical-like feature of the μ3-NH ligand was revealed by electron paramagnetic resonance and magnetic measurements, radical trapping experiments, and computational spin density analysis. In addition, H2 was detected to form during the reaction of 1-RE with NH3, indicating that the radical-like μ3-NH ligand was likely to be generated via N-H bond homolysis. Moreover, the solvents and coordination pattern of β-diketiminate ligands are crucial for the formation of the radical-like μ3-NH ligand from NH3. When toluene instead of n-hexane was used in the reaction of 1-RE with NH3, an array of octaamido tetranuclear RE complexes (3-RE) was obtained. The reaction of the dialkyl yttrium complex (4-Y) bearing a modified β-diketiminate ligand, in which the two mesityl substituents are replaced by a 2,6-diisopropylphenyl group and a 2-(dimethylamino)ethyl group, with NH3 in both n-hexane and toluene only yielded a tetranuclear yttrium complex carrying the dianionic closed-shell μ3-NH ligands (5-Y).

Spectroscopic Properties and Reactivity of a MnIII-Hydroperoxo Complex that is Stable at Room Temperature.

Manganese catalysts that activate hydrogen peroxide have seen increased use in organic transformations, such as olefin epoxidation and alkane C-H bond oxidation. Proposed mechanisms for these catalysts involve the formation and activation of MnIII-hydroperoxo intermediates. Examples of well-defined MnIII-hydroperoxo complexes are rare, and the properties of these species are often inferred from MnIII-alkylperoxo analogues. In this study, we show that the reaction of the MnIII-hydroxo complex [MnIII(OH)(6Medpaq)]+ (1) with hydrogen peroxide and acid results in the formation of a dark-green MnIII-hydroperoxo species [MnIII(OOH)(6Medpaq)]+ (2). The formulation of 2 is based on electronic absorption, 1H NMR, IR, and ESI-MS data. The thermal decay of 2 follows a first order process, and variable-temperature kinetic studies of the decay of 2 yielded activation parameters that could be compared with those of a MnIII-alkylperoxo analogue. Complex 2 reacts with the hydrogen-atom donor TEMPOH two-fold faster than the MnIII-hydroxo complex 1. Complex 2 also oxidizes PPh3, and this MnIII-hydroperoxo species is 600-fold more reactive with this substrate than its MnIII-alkylperoxo analogue [MnIII(OOtBu)(6Medpaq)]+. DFT and time-dependent (TD) DFT computations are used to compare the electronic structure of 2 with similar MnIII-hydroperoxo and MnIII-alkylperoxo complexes.

New Pd(II)-pincer type complexes as potential antitumor drugs: synthesis, nucleophilic substitution reactions, DNA/HSA interaction, molecular docking study and cytotoxic activity.

Two new complexes of Pd(II), [Pd(L1)Cl]Cl (Pd1) and [Pd(L2)Cl]Cl (Pd2), (where L1 = N2,N6-bis(5-methylthiazol-2-yl)pyridine-2,6-dicarboxamide and L2 = N2,N6-di(benzo[d]thiazol-2-yl)pyridine-2.6-dicarboxamide) were synthesized. Characterization of the complexes was performed using elemental analysis, IR, 1H NMR spectroscopy and MALDI-TOF mass spectrometry. The nucleophilic substitution reactions of complexes with L-Methionine (L-Met), L-Cysteine (L-Cys) and guanosine-5'-monophosphate (5'-GMP) were studied by stopped-flow method at physiological conditions (pH = 7.2 and 37 °C). Complex Pd1 was more reactive than Pd2 in all studied reactions, while the order of reactivity of the selected ligands was: L-Met > L-Cys > 5'-GMP. The interaction of complexes with calf thymus-DNA (CT-DNA) was studied by Uv-Vis absorption and fluorescence emission spectroscopy. Competitive binding studies with intercalative agent ethidium bromide (EB) and minor groove binder Hoechst 33258 were performed as well. Both complexes interacted with DNA through intercalation and minor groove binding, where the latter was preferred. Additionally, the interaction of Pd1 and Pd2 complexes with human serum albumin (HSA) was studied employing fluorescence quenching spectroscopy. The results indicate a moderate binding affinity of complexes, with slightly stronger binding of the Pd1. Fluorescence competition experiments with site-markers (eosin Y and ibuprofen) for HSA were used to locate the binding site of Pd1 to the HSA. Additionally, the interaction with DNA and HSA was studied by molecular docking and the revealed results were in good agreement with the experimentally obtained ones. Pd1 complex exhibited cytotoxicity toward human (HCT116) and mouse cell lines (CT26) of colorectal cancer, mouse (4T1) and human (MDA-MB468) breast cancer lines and non-cancerous mouse mesenchymal stem cells (mMSC). In addition, Pd1 complex demonstrated significant selectivity towards cancer cells over non-cancerous mMSC, indicating a high potential to eliminate malignant cells without affecting normal cells. It induced apoptosis in CT26 cells, effectively arrested the cell cycle in the S phase, and selectively down-regulated cyclin D and cyclin E. Moreover, it can alter the expression of cell cycle regulators by increasing p21 and decreasing p-AKT. These findings confirm its ability to disrupt key tumor cell survival signals and suggest that the Pd1 complex is a potent candidate for effective cancer treatment.

Study on Quantum Dynamics of the Na + Na2 Exchanged Reaction and Lifetime Prediction of Na3 Complex Based on the Neural Network Potential Energy Surface.

A high-precision global potential energy surface (PES) is constructed for the Na3 system based on high-level ab initio calculations and the fundamental invariant neural network (FI-NN) method. The root-mean-square error (RMSE) of the PES is 2.88 cm-1. The state-resolved quantum dynamics of the ground-state Na + Na2 (v = 0, j = 0) → Na2 (v', j') + Na reaction is studied using the time-dependent wave packet (TDWP) method on the new PES. Analysis of the relevant integral cross sections revealed a complicated energy-transfer mechanism during collisions. Similarly, the characteristics of the differential cross sections indicate that the complex-forming mechanism plays a dominant role in the reaction, providing conditions for a comprehensive exploration of the lifetimes of the complexes. Based on the Rice-Ramsperger-Kassel-Marcus (RRKM) theory, the calculated lifetime of the Na3 complex is approximately 3.9 ns.

Carboxyl-Group-Bearing Metal Corroles of Cobalt, Manganese and Copper for Electrocatalytic Hydrogen Evolution.

5,15-bis(perfluorophenyl)-10-(4-carboxyphenyl) corrole and its Co(III), Mn(III), and Cu(III) corrole complexes were synthesized. The electrocatalytic hydrogen evolution reaction (HER) of these metal corrole complexes was investigated using different proton sources (AcOH, trifluoroacetic acid, and TsOH) in an organic dimethylformamide solvent. The electrocatalytic HER may proceed through EECC, EECEC, or EEECEC pathways (where E represents electron transfer and C represents proton binding) depending on the acidity and concentration of the proton source used. The Co corrole complex exhibits remarkable hydrogen production performance, achieving a turnover frequency of 201 s-1 and a catalytic efficiency of 1.00. The examined metal corrole complexes also exhibit good HER activity in aqueous solution, with their catalytic activity following an order of 1-Co > 1-Cu > 1-Mn in both organic and aqueous phases.

Reactivity of Strontium Hydride Supported by the Superbulky Hydrotris(pyrazolyl)borate Ligand.

Hydrogenolysis of [(TpAd,iPr)Sr{CH(SiMe3)2}] (1) (TpAd,iPr = hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate) in hexane solution under 20 atm of H2 allowed for the isolation of strontium hydride [(TpAd,iPr)Sr(μ-H)]2 (2) in good yield. Complex 2 exhibits the dimeric nature in solid state, featuring two different bond modes between the Sr center and TpAd,iPr ligand. Treatment of complex 2 with PhC(H)═NtBu or PhCH2Bpin (Bpin = pinacolateborane) afforded the strontium amide complex [(TpAd,iPr)Sr{N(CH2Ph)(tBu)}] (4) and hydroborate complex [(TpAd,iPr)Sr{μ-HBpin(CH2Ph)}] (5), respectively. Reactions of complex 2 with 2-picoline, 2-phenylquinoline, or 2-phenylpyridine led to the formation of strontium 2-pyridylmethylene/2-picoline complex [(TpAd,iPr)Sr(2-CH2-Py)(2-picoline)] (6), reductively coupling diphenyl-biquinolide complex [{(TpAd,iPr)Sr}2(2,2'-Ph2-4,4'-dihydro-4,4'-biquinolide)] (7), and diphenyl-bipyridyl radical complex [(TpAd,iPr)Sr(6,6'-Ph2-2,2'-bipyridyl)] (8), separately. All of the complexes have been well characterized, including NMR spectrum and single-crystal X-ray analysis.

Photoinduced Self-assembly: An Alternative Strategy for the Construction of Coordination Oligomers and Polymers.

Self-assembled oligonuclear and polynuclear complexes have numerous functionalities and potential applications. Generally, such compounds have been constructed by thermal substitution reactions with bridging ligands. Herein, we report bottom-up and photochemical construction of functional coordination oligomers and polymers by photosubstitution-induced self-assembly. The photosubstitution reactions of a ruthenium precursor complex with bridging ligands having pyrazole moieties afford mono-, di-, tri-, tetra-, and pentanuclear ruthenium complexes, Ru1-Ru5, which have one-dimensional architectures. Intramolecular hydrogen bonding between each bridging ligand is a key to construct the molecular nanowires. All the complexes have been isolated and thoroughly characterized. The photochemically synthesized ruthenium complexes act as synthons for longer metal-complex-based nanowires with a length of the order of tens-of nanometers. The multinuclear complexes are generated by photoinduced self-assembly in the presence of a base, and they undergo photoinduced disassembly in the presence of acid.

Некоторые особенности токсикологических свойств специфического иммунобиостимулятора «Трансфер-фактор» в доклинических испытаниях

Abstract. The purpose of the study is to evaluate some aspects of toxicological safety of a specific immunobiostimulant “Transfer factor” in laboratory animal models. Methods. The experiments were performed on mice, rats and guinea pigs. The toxicological safety assessment of the “Transfer factor” preparation included the determination of the following characteristics: chronic toxicity, assessment of specific activity, assessment of embryotoxic and teratogenic properties, assessment of allergenic properties Results. It was established that the introduction of the “Transfer factor” preparation in a chronic toxicological experiment is accompanied by the development of muscle tremor in the rodents’ body, the duration of which depends on the administered dose, route of administration and exposure time, but their body weight increases by 6.29–10.63 %. Autopsy of experimental group animals revealed no visible changes in the arrangement of internal organs and fluid accumulation in the abdominal and pleural cavities, although some pathological changes in color, consistency and size of the lungs, spleen, liver and heart were noted. The mass coefficients of these organs change with an increase in the dose of the administered drug “Transfer factor”, especially with the intraperitoneal route of administration up to 10.39 %. The tested drug in the reaction of lymphocyte blast transformation increases the number of blasts from 0.20 to 1.40 %. The totality of data allows us to state that the drug “Transfer factor” in accordance with GOST 12.1.007-76 belongs to the IV hazard class “low-hazard substances” and it can be recommended for further clinical trials, in which a dosage exceeding 6 ml/kg of live weight will not be used, when administered to laboratory animals, a complex of changes in the internal organs develops. Scientific novelty. The introduction of “Transfer factor” does not affect the condition and functions of the reproductive organs (uterus, ovaries) of pregnant rats, and the drug does not exhibit a negative embryotoxic and teratogenic effect in their body. When studying the allergenic properties of the drug, it was found that it does not cause a general anaphylaxis reaction in the body of guinea pigs, does not irritate the skin in the reaction of immune complexes and the conjunctiva of the eye in the conjunctival test.

Ruthenium methoxy and ruthenium vinylidene complexes featuring dithiocarbamate ligands

Treatment of [(Me3tacn)RuIII(κ2-S2CNR2)Cl]PF6 (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) with methanol in the presence of zinc powder in air afforded four ruthenium methoxy complexes [(Me3tacn)RuIII(κ2-S2CNR2)(OCH3)]PF6 (R = Me 1, Et 2, nPr 3, iPr 4). Further reactions of complexes 1–4 and phenylacetylene gave four ruthenium vinylidene complexes [(Me3tacn)(κ2-S2CNR2)Ru=C=CHPh]PF6 (R = Me 5, Et 6, nPr 7, iPr 8). Molecular structures of complexes 1, 2, 3, 6, 7 and 8 were established by single crystal X-ray diffraction analysis. Moreover, all complexes were characterized by infrared, UV–vis, fluorescence and mass spectrometry, and their electrochemical properties were also investigated. The visible-light-induced catalytic properties of complexes 5–8 for H2 evolution by water splitting were explored.

Synthesis and Characterization of s-Triazine Cored Schiff Base Containing β-lactam and Its [M(Salen/Saloph)] (M= Cr3+ and Fe3+) Capped Complexes

This study consists of a tripodal 6-iminopenicylanic acid ligand synthesized based on the s-triazine group and its four trinuclear complexes. For this purpose, 2,4,6-tri(p-formylphenoxy)-1,3,5-triazine (III) (TRIPOD) was obtained from the reaction of 2,4,6-trichloro-1,3,5-triazine and 4-hydroxybenzaldehyde. Then, tripodal target ligand (V) was obtained from the reaction of TRIPOD and 6-aminopenicylanic acid. Finally, tripodal trinuclear (ML) capped target complexes were obtained from the reactions of the initial complexes [(ML)2O] (M= Cr3+ or Fe3+, L= Salen or Saloph) with the target ligand in methanol media. The structures of all obtained ligands were elucidated using 1H NMR, FT-IR, and elemental analysis methods. The structures of the complexes were characterized using FT-IR, magnetic susceptibility, ICP-OES, and TGA methods.

Synthesis of Dinuclear Cobalt Silylene Complexes and Their Catalytic Activity for Alkene Hydrosilylation Reactions.

A novel dinuclear silylene cobalt complex [((Me3P)2Co)(PMe2)(CoCl(PMe3))(Si(NCH2PPh2)2C6H4)] (1) supported by the [PSi(silylene)P] ligand was prepared through the reaction of N-heterocyclic [PSiP] pincer ligand L1 (HSiCl(NCH2PPh2)2C6H4) with Co(PMe3)4. Complex [((Me3P)2Co)2(Si(NCH2PPh2)2C6H4)] (2) was formed through the reaction of complex 1 with MeLi. To the best of our knowledge, complexes 1 and 2 are the first examples of dinuclear silylene cobalt complexes supported by the [PSi(silylene)P] ligand. A new preligand L2 (SiCl2(NCH2PPh2)2C6H4) was synthesized, and the reaction of preligand L2 with Co(PMe3)4 afforded silyl cobalt complex [((Me3P)2Co)(SiCl(NCH2PPh2)2C6H4)] (3). The reaction of 3 with CO delivered cobalt carbonyl complex [((Me3P)(CO)Co)(Si(NCH2PPh2)2C6H4)]2O (4). The catalytic activity of cobalt complexes 1-4 on the hydrosilylation of alkenes was explored. Among the four complexes, complex 1 has the best catalytic activity. The catalytic process could be promoted with NaBHEt3 as an additive, and a complete conversion with an excellent selectivity of 98:2 (b/l) could be reached at 120 °C within 8 min for aryl alkenes. A possible catalytic cycle was proposed on the basis of the experimental results and literature reports, with a cobalt hydride complex as an active intermediate. The molecular structure of complexes 1-4 was determined by single-crystal X-ray diffraction analysis.

N[sbnd]O bond cleavage and N2 activation reactions of the Nitrosyl-Bridged complex [Mo2Cp2(µ-PtBu2)(µ-NO)(NO)2]

The title compound was prepared through a three-step procedure starting with the hydride complex [Mo2Cp2(µ-H)(µ-PtBu2)(CO)4], which was first dehydrogenated through reaction with HBF4·OEt2 to give the unsaturated complex [Mo2Cp2(µ-PtBu2)(CO)4](BF4) (Mo=Mo), which displays a transoid structure according to experimental (Mo-Mo = 2.8283(7) Å) and Density Functional Theory studies. The latter was then reacted with NO to give the dinitrosyl derivative [Mo2Cp2(µ-PtBu2)(CO)2(NO)2](BF4), which in turn was further decarbonylated and nitrosylated upon reaction with [N(PPh3)2]NO2 to give the title nitrosyl-bridged complex (Mo-Mo = 2.905(1) Å). This complex displayed a structure comparable to that of its PCy2-bridged analogue, with similar pyramidalization of the bridging nitrosyl, but a more pronounced folding of the central MoPMoN skeleton and bending of terminal nitrosyls. It also displayed a similar NO bond activation chemistry, as shown by its reactions with HBF4·OEt2 to give the nitroxyl-bridged complex [Mo2Cp2(µ-PtBu2)(µ-k1:η2-HNO)(NO)2](BF4) (HNO = 1.330(8) Å), with P(OEt)3 to give the phosphoraniminate-bridged complex [Mo2Cp2(µ-PtBu2){µ-NP(OEt)3}(NO)2], and with Na(Hg) to give the amide-bridged derivative [Mo2Cp2(µ-PtBu2)(µ-NH2)(NO)2]. Under a nitrogen atmosphere, however, the latter reaction also gave a minor side product identified as the dinitrogen-bridged derivative [Mo4Cp4(µ-PtBu2)2(µ4-N2)(NO)4]. This tetranuclear complex displays a dinitrogen molecule bridging four metal atoms in the novel µ4-k1:k1:k1:k1 coordination mode, with strong metal-nitrogen interactions taking the N2 ligand to the diazendiide (N22-) limit (NN = 1.241(3) Å).

Identity of the Silyl Ligand in an Iron Silyl Complex Influences Olefin Hydrogenation: An Experimental and Computational Study.

In this study, we explore the selective synthesis of iron silyl complexes using the reaction of an iron mesityl complex (MesCCC)FeMes(Py) with various hydrosilanes. These resulting iron silyl complexes, (MesCCC)Fe(SiH2Ph)(Py)(N2), (MesCCC)Fe(SiMe2Ph)(Py)(N2), and (MesCCC)Fe[SiMe(OSiMe3)2](Py)(N2), serve as effective precatalysts for olefin hydrogenation. The key to their efficiency in catalysis lies in the specific nature of the silyl ligand attached to the iron center. Experimental observations, supported by density functional theory (DFT) simulations, reveal that the catalytic performance correlates with the relative stability of dihydrogen and hydride species associated with each iron silyl complex. The stability of these intermediates is crucial for efficient hydrogen transfer during the catalytic cycle. The DFT simulations help to quantify these stability factors, showing a direct relationship between the silyl ligand's electronic and steric properties and the overall catalytic activity. Complexes with certain silyl ligands exhibit better performance due to the optimal balance between the stability and reactivity of the key active catalyst. This work highlights the importance of ligand design in the development of iron-based hydrogenation catalysts.

Potassium, ytterbium(II), and samarium(III) alkoxide complexes containing the <i>tris</i>((2-dimethylaminomethyl)phenyl)methoxide ligand: synthesis and structures

The reaction oftris((2-dimethylaminomethyl)phenyl)methanol ((2-Me2NCH2C6H4)3COH) with potassium hydride in THF at –35°C affords dimeric alkoxide {[(2-Me2NCH2C6H4)3CO]K(THF)}2(I) in a yield of 90%. The reaction of compound I with YbI2(THF)2(1 : 1, 25°C) gives the Yb(II) alkoxyiodide complex {[(2-Me2NCH2C6H4)3CO]Yb(μ-I)(THF)2}2(II) in a yield of 57%. Complex II in the crystalline state is dimeric due to two bridging iodide ligands. Unlike the Yb(II) compound, the exchange reaction of complex I with SmI2(THF)2 (1 : 1, 25°C) in THF followed by the addition of dimethoxyethane (DME) involves the oxidation of the metal to form the trivalent samarium complex [(2-Me2NCH2C6H4)3CO]2SmI (III), which is isolated in a yield of 60%. The molecular structures of the complexes are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2259700 (I), 2259701 (II), and 2259702 (III)).

Iron-Catalyzed Electrophotochemical α-Functionalization of a Silylcyclobutanol.

Four-membered ring structure is important in organic chemistry, and selective cleavage and functionalization of these strained rings are of great interest. However, direct α-functionalization of cyclobutanols is rarely reported because of the high O-H bond dissociation energy and the occurrence of β-scission of C-C bonds in these alcohols. Recently, transition-metal catalysis has facilitated alkoxy radical generation. Herein, we report a method for electrophotochemical α-functionalization of a silylcyclobutanol via visible-light-induced LMCT reactions of M-alkoxy complexes. Introduction of the silyl group into the cyclobutanol structure favored fast [1,2]-silyl transfer over ring opening, thus allowing the generation of α-functionalized products.