Syntheses of a 2,6-bis-(methylphospholyl)pyridine ligand and its cationic Pd(II) and Ni(II) complexes - application in the palladium-catalyzed synthesis of arylboronic esters

2,6-Bis(2,5-diphenylphospholyl-1-methyl)pyridine (2) was prepared from the reaction of 2,5-diphenylphospholide anion with 2,6-bis(chloromethyl)pyridine. The X-ray crystal structure of 2 was recorded. Reaction of 2 with [Pd(COD)Cl₂] in the presence of AgBF₄ yields the cationic complex [Pd(2)Cl][BF₄] (3). The analogous Ni complex [Ni(2)Br][BF₄] (4) was prepared in a similar way by reacting ligand 2 with [NiBr₂(DME)] in the presence of AgBF₄ and its formulation was confirmed by an X-ray crystal structure study. Complex 3 efficiently catalyzes the coupling between pinacolborane and iodo and bromoarenes with good TON (up to 1 × 10⁵ with iodo derivatives and 8.9 × 10³ with bromo derivatives).     

Organometallic chemistry of 15-membered tri-olefinic macrocycles: catalysis by palladium(0) complexes in carbon-carbon bond-forming reactions

15-Membered macrocycles (E,E,E)-1,6,11-tris(arenesulfonyl)-1,6,11-triazacyclopentadeca-3,8,13-trienes (1) are prepared from arenesulfonamides and trans-1,4-dibromo-2-butene. Macrocycles 1 coordinate palladium(0), platinum(0), and silver(I). The palladium complexes are useful and reutilizable catalysts or precatalysts in Suzuki cross-couplings, butadiene telomerizations, hydroarylation of alkynes, and in the Heck reaction. Structurally related macrocycles are also available by similar synthetic procedures.     

Ruthenium catalysis in six-membered O-heterocycles synthesis

Due to significant biological activity associated with N-, O-, and S-heterocycles, several reports for their synthesis have appeared in recent decades. Traditional approaches require expensive or highly specialized equipment or would be of limited use to the synthetic organic chemist due to their highly inconvenient approaches. This review summarizes the applications of ruthenium metal with emphasis of their synthetic applications for oxygen-containing six-membered heterocylces. In summary, this review article describes the synthesis of heterocyclic rings containing different heteroatoms.     

Anions as templates in coordination and supramolecular chemistry

This review aims to highlight the most important recent advances in the area of anion-templated syntheses in supramolecular and coordination chemistry. We published a comprehensive review on this area in 2003 and hence examples prior to this date will only be discussed when essential for clarity of presentation. The current review has been divided into three main sections: (a) anion-templated synthesis of systems with well-defined molecular weights; this includes macrocycles and cages, interlocked species (such as catenanes and rotaxanes), helical assemblies and other selected examples. (b) Anions as templates in polymeric systems; this includes metal-organic frameworks, molecularly imprinted polymers and other selected examples, such as liquid crystalline materials. (c) Anion templates in dynamic combinatorial libraries.     

P-Modular bis(phosphines) based on the 1,2-trans-disubstituted cyclopentane framework in synthesis, coordination chemistry, and catalysis

The review describes a class of versatile bidentate phosphines having a homochiral 1,2-disubstituted cyclopentane backbone, the use of such ligands in coordination chemistry, and their application in transition metal-catalyzed synthesis, including CH activation, CC coupling, CC hydrogenation, and hydroformylation. In particular, the synthetic potential of the multi-purpose PH and PCl reagents (R,R)- and (S,S)-C₅H₈(PX₂)₂ (X = H, Cl) is highlighted, since these open up the possibility to incorporate virtually any other PO-, PN- or PC-bonded residue (“module”) into the homochiral bis(phosphine) framework. The resulting chelate ligands allow access to transition metal catalysts with stereodiscriminating properties determined by parameters such as (i) the presence of P-substituents that are equal or pairwise different in steric demand, (ii) the spatial orientation of such substituents with respect to the coordination plane of the catalyst complex, and (iii) the combination of C- and P-chirogenic stereoelements in matched (or mismatched) fashion. A comparative discussion of the crystal structures that are currently available for the free ligands and their transition metal complexes is also presented.     

Phase transfer catalysis in the chemistry of five-membered nitrogen-containing heterocycles

The methods for synthesis and reactions of five-membered nitrogen-containing heterocycles under the conditions of phase transfer catalysis as well as the application of quaternized heterocycles as phase transfer catalysts are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2115–2121, November, 1995.     

Anion coordination chemistry in aqueous solution of polyammonium receptors

The behavior of polyamines as receptors of selected families of anions in water is explored. First metallocyanide interaction with saturated polyammonium hosts is analyzed both in solution and in the solid state. The utility of potentiometry, multinuclear NMR, microcalorimetry and cyclic voltammetry to describe solution features of this chemistry is described for selected systems. Sulfate, phosphate, polyphosphate and nucleotide interactions with large polyammonium receptors are then reviewed. Hydrogen bond formation is discussed from a thermodynamic point of view. The influence of the presence of aromatic fragments within the structure on the binding strength is discussed. Factors affecting ATP hydrolytic cleavage by macrocyclic polyammonium receptors is revisited. Metal complexes are analyzed as anion receptors through formation of mixed complexes. Finally, an example of the influence of anion in crystal growing is provided.     

Advances in 2H-azirine chemistry: A seven-year update

2H-Azirines are versatile building blocks for the preparation of various nitrogen-containing heterocycles. Seven years ago the comprehensive review on azirine chemistry was published in Tetrahedron. Since then, there had been an explosion of research activities in the field of these strained molecules. This renaissance is primarily associated with the discovery of new reactivity of azirines and in particular new catalytic and light-induced reactions, which made possible unusual transformations of this three-membered N-heterocycle into azole and azine derivatives as well as polyheterocyclic systems. The second reason for the progress of azirine chemistry is the development of methods for the preparation of new azirine derivatives. The third reason is the discovery of new synthetic equivalents of azirines, which permitted avoiding the use of unstable azirines in some modern catalytic procedures. In the present comprehensive review, we have placed particular emphasis on discussing the new developments in the synthesis and reactivity of azirines for the period from 2012 until the end of 2018.     

Novel benzoferrocenyl chiral ligands: Synthesis and evaluation of their suitability for asymmetric catalysis

Four benzoferrocenyl phosphorus chiral ligands were conveniently prepared in good overall yields. These ligands were found to be stable in solid form and in solution. Two of the four ligands were resolved by chiral HPLC. Unlike a reported bis(phosphino-η⁵-indenyl)iron(II) complex, in which the indenyl ligands undergo ring flipping through an η¹-intermediate, these two ligands were found to be configurationally stable in solution and in solid state. The suitability of these ligands for enantioselective catalysis was assessed in studies on allylic alkylation reactions. When the two less sterically hindered ligands were used, excellent chemical yields were obtained, but the other two more sterically hindered ones gave lower yields. When the two enantiopure ligands were used, enantioselectivity of up to 51% ee was observed. These findings suggest that benzoferrocene derivatives may be used as chiral ligands for asymmetric catalysis.     

Sterically hindered cyclopentadienyl and phospholyl ligands in dysprosium chemistry

Three new unsolvated organometallic complexes of dysprosium(III) with very sterically hindered π-ligands have been synthesized and structurally characterised: the monomeric bis[η⁵-(1,2,4-tris-trimethylsilylcyclopentadienyl)]iododysprosium (1b), bis[η⁵-(1,4-bis-t-butyl-2,3-dimethylphospholyl)]iododysprosium, (1c) and the dimeric tetrakis[η⁵-(1,4-bis-t-butyl-2,3-dimethylphospholyl)]bis(μ-iodo)di-dysprosium (1d). The relative steric bulk of the π-ligands have been assessed by comparison of the structural data of 1b–d with that of the previously described bis[η⁵-(1,2,4-tris-t-butylcyclopentadienyl)]iododysprosium (1a). Contrary to 1a, reduction attempts on 1b–d were unsuccessful. The reaction of the dysprosium(II) complex bis[η⁵-(1,2,4-tris-t-butylcyclopentadienyl)]dysprosium(μ-bromo)-potassium[18]crown-6 (3) with fluorenone resulted in its monoelectronic reduction and coordination of the resulting ketyl to dysprosium(III): isolation of potassium[18]crown-6 bis[η⁵-(1,2,4-tris-t-butylcyclo-pentadienyl)](fluorenone ketyl)bromodysprosate (4) that was structurally characterised.     

Review of electrochemical studies of complexes containing the Fe2S2 core characteristic of [FeFe]-hydrogenases including catalysis by these complexes of the reduction of acids to form dihydrogen

This article reviews published literature on the electrochemical reduction and oxidation of complexes containing the Fe₂S₂ core characteristic of the active site of [FeFe]-hydrogenases. Correlations between reduction and oxidation potentials and molecular structure are developed and presented. In cases where the complexes have been studied with regard to their ability to catalyze the reduction of acids to give dihydrogen, the overpotentials for such catalyzed reduction are presented and an attempt is made to estimate, at least qualitatively, the efficiency of such catalysis.     

Disclosing Support-Size-Dependent Effect on Ambient Light-Driven Photothermal CO2 Hydrogenation over Nickel/Titanium Dioxide

The size of support in heterogeneous catalysts can strongly affect the catalytic property but is rarely explored in light-driven catalysis. Herein, we demonstrate the size of TiO₂ support governs the selectivity in photothermal CO₂ hydrogenation by tuning the metal-support interactions (MSI). Small-size TiO₂ loading nickel (Ni/TiO₂-25) with enhanced MSI promotes photo-induced electrons of TiO₂ migrating to Ni nanoparticles, thus favoring the H₂ cleavage and accelerating the CH₄ formation (227.7 mmol g⁻¹ h⁻¹) under xenon light-induced temperature of 360 °C. Conversely, Ni/TiO₂-100 with large TiO₂ prefers yielding CO (94.2 mmol g⁻¹ h⁻¹) due to weak MSI, inefficient charge separation, and inadequate supply of activated hydrogen. Under ambient solar irradiation, Ni/TiO₂-25 achieves the optimized CH₄ rate (63.0 mmol g⁻¹ h⁻¹) with selectivity of 99.8 %, while Ni/TiO₂-100 exhibits the CO selectivity of 90.0 % with rate of 30.0 mmol g⁻¹ h⁻¹. This work offers a novel approach to tailoring light-driven catalytic properties by support size effect.     

The synthesis, coordination chemistry and ethylene polymerisation activity of ferrocenediyl nitrogen-substituted ligands and their metal complexes

Treatment of aminoferrocene with substituted 2-hydroxybenzaldehydes yields the air- and moisture-stable ligands 1–4, which were then reacted to form the chromium dichloride complexes 5–7 and the nickel bis-chelate species 8 and 9. The metal compounds are very air-sensitive but the chromium compounds act as pre-catalysts for the polymerisation of ethylene. Reaction of 1,1′-bis(amino)ferrocene with similarly substituted 2-hydroxybenzaldehyes or simple benzaldehyde gives the ligands 10–12 and 17, respectively. The X-ray crystal structure of 11 shows the molecule to have non-crystallographic C₂ symmetry and to be linked by C–Hπ interactions between the anthracene rings. Titanium-containing complexes 13–16 can be formed utilising ligands 10–12 and there is a change in geometry within the complexes dependent on the adjacent co-ligands, whilst ligand 17 can be reacted with PdClMe(COD) to form the chelate complex 18. Cyclic voltammetric studies have been carried out on 18 and its oxidised analogue 19, but both complexes are inactive towards ethylene polymerisation.     

From neutral iminophosphoranes to multianionic phosphazenates. The coordination chemistry of imino-aza-P(V) ligands

This review deals with the chemistry and coordination behaviour of imino-aza phosphorus(V) ligands focussing on s- and p-block as well as Group 11 and 12 metal complexes. Imino phosphorus(V) ligands contain one or more terminal RNP-units, which include iminophosphoranes R₃PNR′, monoanionic diiminophosphinates [R₂P(NR′)₂]⁻, dianionic triiminophosphonates [RP(NR′)₃]²⁻ and trianionic tetraiminophosphates [P(NR′)₄]³⁻. Aza-phosphorus(V) ligands feature bridging PNP units, which include cyclic and polymeric phosphazenes [R₂PN]_n. Imino-aza- phosphorus(V) ligands containing both imino and aza functions include linear diiminodiphosphazenates [N{R₂P(NR′)₂}₂]⁻ and multianionic poly(imino) cyclophosphazeantes such as [N₄{RP(NR′)}₄]⁴⁻ and [N₃{P(NR′)₂}₃]⁶⁻. Imino-aza phosphorus(V) ligands are assembled of three basic building blocks: the cationic tetravalent phosphonium centre (P), the anionic divalent amido function (N) and the terminally arranged R-group. The overall negative charge Z of the resulting ligand system is equal to the difference between the number of P and the number of N-centres: Z=n(P)n(N). Imino-aza phosphorus(V) ligands are electron rich N-donor ligands which co-ordinate via both N(imino) and N(aza) functions and have been applied in numerous metal complexes in order to stabilise low coordination numbers, unusual oxidation states and bonding modes or serve as ligands in homogeneous catalysis. The R-group provides both steric bulk and solubility in non-polar solvents. Multianionic phosphazenates feature a polydentate ligand surface, which facilitates an extremely high metal load. PN units of iminophosphoranes and phosphazenes have acceptor properties and enhance the acidity of α-alkyl and ortho-aryl protons. Deprotonation of P-alkyl and P-aryl iminophosphoranes give ligand systems featuring C,N chelating sites, which are also discussed.     

Spirocyclic diaminocarbenes: synthesis, coordination chemistry, and investigation of their dimerization behavior

Nonaromatic, "saturated", spirocyclic N-heterocyclic diaminocarbenes 11 can be obtained from spirocyclic imidazolidin-2-thiones 10 by reductive desulfurization with potassium. The unsymmetrically N,N'-substituted spirocyclic imidazolidin-2-thiones were obtained by reaction of ketimines 9 with lithium N-butyl-N-lithiomethyldithiocarbamate (6). 13C NMR spectroscopy revealed that the unsymmetrically N,N'-substituted spirocyclic imidazolidin-2-ylidene 11 a undergoes a slow, acid-catalyzed dimerization to give the enetetramine 11 a=11 a, which exists in two isomeric forms (syn and anti). This reaction is reversible under special circumstances. Carbenes of type 11 react with [W(CO)6] to yield air-stable carbene complexes of type [W11(CO)5] (14). The molecular structures of two derivatives 14 a and 14 b were established by X-ray crystallography and show clear distortion of the five-membered N-heterocyclic ring, caused by the spirocyclic molecular structure of the carbene ligands of type 11.     

A Nanocomposite of Bismuth Clusters and Bi2O2CO3 Sheets for Highly Efficient Electrocatalytic Reduction of CO2 to Formate

The renewable-electricity-driven CO₂ reduction to formic acid would contribute to establishing a carbon-neutral society. The current catalyst suffers from limited activity and stability under high selectivity and the ambiguous nature of active sites. Herein, we report a powerful Bi₂S₃-derived catalyst that demonstrates a current density of 2.0 A cm⁻² with a formate Faradaic efficiency of 93 % at −0.95 V versus the reversible hydrogen electrode. The energy conversion efficiency and single-pass yield of formate reach 80 % and 67 %, respectively, and the durability reaches 100 h at an industrial-relevant current density. Pure formic acid with a concentration of 3.5 mol L⁻¹ has been produced continuously. Our operando spectroscopic and theoretical studies reveal the dynamic evolution of the catalyst into a nanocomposite composed of Bi⁰ clusters and Bi₂O₂CO₃ nanosheets and the pivotal role of Bi⁰−Bi₂O₂CO₃ interface in CO₂ activation and conversion.     

单原子材料在二氧化碳催化中的技术经济分析与产业化应用前景

近年来, 随着科学研究的不断深入, 单原子催化剂由于具有高活性与高选择性等突出特点被广泛挖掘和应用. 作为连接多相与均相催化的桥梁, 单原子催化剂已经成为催化领域的重要研究对象之一, 具有广泛的工业化应用前景. 本文对单原子催化剂的发展历程、 特点及其在不同领域的应用进行了概括, 综合评述了当前CO₂还原领域的技术经济分析, 并首次对单原子材料催化转化CO₂进行了技术经济分析与计算. 最后, 对单原子催化剂在CO₂还原领域中工业化应用的未来发展方向及亟需解决的关键科学和技术问题进行了展望, 以期推动单原子催化材料的进一步广泛应用.     

Suppressive Strong Metal-Support Interactions on Ruthenium/TiO2 Promote Light-Driven Photothermal CO2 Reduction with Methane

Strong metal-support interactions (SMSI) have gained great attention in the heterogeneous catalysis field, but its negative role in regulating light-induced electron transfer is rarely explored. Herein, we describe how SMSI significantly restrains the activity of Ru/TiO₂ in light-driven CO₂ reduction by CH₄ due to the photo-induced transfer of electrons from TiO₂ to Ru. In contrast, on suppression of SMSI Ru/TiO₂−H₂ achieves a 46-fold CO₂ conversion rate compared to Ru/TiO₂. For Ru/TiO₂−H₂, a considerable number of photo-excited hot electrons from Ru nanoparticles (NPs) migrate to oxygen vacancies (OVs) and facilitate CO₂ activation under illumination, simultaneously rendering Ru^δ+ electron deficient and better able to accelerate CH₄ decomposition. Consequently, photothermal catalysis over Ru/TiO₂−H₂ lowers the activation energy and overcomes the limitations of a purely thermal system. This work offers a novel strategy for designing efficient photothermal catalysts by regulating two-phase interactions.     

Lanthanide(III) nitrobenzenesulfonates and p-toluenesulfonate complexes of lanthanide(III), iron(III), and copper(II) as novel catalysts for the formation of calix[4]resorcinarene

Lanthanide(III) salts of p-toluenesulfonic acid [lanthanide(III) tosylates, Ln(TOS)₃] and nitrobenzenesulfonic acid [Ln(NBSA)₃], and p-toluenesulfonate complexes of iron(III) and copper(II) were prepared, characterized, and examined as catalysts for the synthesis of resorcinol-derived calix[4]resorcinarenes. The reaction of resorcinol with benzaldehyde yields two isomers, the all-cis isomer (rccc) and the cis-trans-trans isomer (rctt) with the relative isomer ratios depending on the reaction conditions. However, in the reaction of resorcinol with octanal only one isomer, the all-cis isomer, is formed in high yields with less than 0.1 mol % of Yb(TOS)₃. Examination of lanthanide(III) tosylates and lanthanide(III) nitrobenzenesulfonates revealed that ytterbium(III) 4-nitrobenzenesulfonate [ytterbium(III) nosylate, Yb(4-NBSA)₃] and ytterbium(III) 2,4-dinitrobenzenesulfonate [Yb(2,4-NBSA)₃] are the most active catalysts. The catalysts could be easily recovered and reused several times for resorcinarene formation without loss of efficiency. Surprisingly good results were also obtained with iron(III) and copper(II) p-toluenesulfonates. Besides optimizing the reaction conditions, new insights into the reaction mechanism were also obtained.     

Some chelating C-donor ligands in hydrogen transfer and related catalysis

Recent work is discussed that throws light on synthetic, steric, and electronic aspects of NHC complexes as well as on outer sphere effects in their reactivity. The chemistry of the NHC ligand is much more complex than the more traditional phosphines and provides much greater possibilities for altering steric and electronic properties for tuning reactivity. In synthetic work the Lin Ag₂O method is shown to be inapplicable to the synthesis of abnormal NHCs bound via C-4(5) where the C2 position is blocked with CH₃, because Ag(I) oxidizes the CH₃ group to formate with formation of the normal C-2 bound Ag-NHC. Linker effects on the behavior of chelating NHCs depend on the linker locking the azole rings into a conformation that depends on linker length. This gives rise to different complexes being formed when different linker lengths are employed. The failure of M-NHC bonds to reversibly dissociate can prevent potentially chelating bis and tris NHC precursors from forming the desired products but instead being trapped in a kinetic nonchelate form. Imidazolium carboxylates prove to be synthetically useful in that they can act as excellent NHC transfer agents to a variety of transition metals. The Tolman electronic parameter of NHCs can be determined by a variety of experimental and computational methods. Anion dependent chemistry can give rise to a switching of the product of imidazolium salt metallation from normal (C-2) to abnormal (C-4(5)) forms.