It has been experimentally shown that N-heteroaryl-substituted α-diphenylphosphinoglycines N-(pyrazin-2-yl)-α-diphenylphosphinoglycine, N-(pyridin-2-yl)-α-diphenylphosphinoglycine and N-(pyrimidin-2-yl)-α-diphenylphosphinoglycine obtained by the reaction of three-component condensation of diphenylphosphine, the corresponding primary amine and glyoxylic acid monohydrate are capable in combination with Ni(COD)₂, where COD is cyclooctadiene-1,5, to form active forms of catalysts for selective homogeneous dimerization and trimerization of ethylene with the formation of butene-1 and hexene-1 as the main products. It has been established that the obtained organo-nickel catalytic systems provide a yield of short-chain (C₄–C₆) olefins at the level of 90% with a selectivity for linear α-olefins of 97%. The study of the influence of temperature on the process of homogeneous ethylene oligomerization using the obtained compounds made it possible to establish that the optimal temperature for ethylene oligomerization, providing the highest selectivity to butene-1 and hexene-1, is 80–105°C at the optimum pressure of ethylene is 20–35 atm. Under these conditions, the selectivity for butenes is 71.4–72.6% (selectivity for butene-1 – 69.3–71.1%), for hexenes 20.6–21.2% (selectivity for hexene-1 – 19.2–19.5%), and the optimal duration of the oligomerization process at a temperature 105°C is 1.5 h, which provides the rate of formation of butene-1 equal to 168.1 golig gNi⁻¹h⁻¹) and the rate of formation of hexene-1 – 47.3 golig gNi⁻¹h⁻¹).

A novel organonickel sigma-complex [NiBr(Tcpp)(bpy)], where Tcpp is 2,4,6-tricyclopentylphenyl, bpy is 2,2'-bipyridine has been generated in solution by electrochemical macroscale synthesis. The monitoring of the macroscale electrosynthesis and also the cyclic voltammetric measurements have shown that the organonickel sigma-complex is formed at the electrolysis but, in contrast to its analogues with ortho -substituted aromatic fragments, is unstable and decomposes to the homo-coupling product, namely, the earlier unknown sterically hindered biaryl derivative 2,2',4,4',6,6'-hexacyclopentyl-1,1'-biphenyl, the molecular and crystal structure of which are described by NMR spectroscopy and X-ray diffraction techniques.

An Erratum to this paper has been published: https://doi.org/10.1134/S1023193524010087

In this work chromia-alumina catalysts have been studied by the electron paramagnetic resonance (EPR) spectroscopy in the temperature range-120-200 ?. It was observed, that the activity of the catalysts in the dehydrogenation of n-butane and i-butane correlates with the amount of strongly interacting Cr3+ ions of the amorphous chromia phase. A disproportionate increase in the antiferromagnetic coupling energy delta E between Cr3+ ions was shown in the concentration range 4.7-9.8%wt.Cr (from 210 to 420 cm(-1)) and 9.8-13.3%wt.Cr (from 420 to 450 cm(-1)). It was established, that an increase in the exchange interaction between Cr3+ ions is more favourable for the dehydrogenation of i-butane as compared to n-butane.

In the present study, a mathematical model of the isobutane dehydrogenation process for a laboratory reactor with a diameter of 2.8 cm and a height of 70 cm was created using CFD methods. A two-fluid model was selected as a model for the fluidization simulation, when the gas and solid granular phases were considered as continuous. The model of chemical kinetics considers three reactions that make the main contribution to the products mass fraction at the reactor outlet: the reaction of catalytic dehydrogenation of isobutane to isobutylene, the reaction of thermal cracking of isobutylene with the formation of methane and propylene, and the reaction of catalytic hydrogenation of propylene. The model was verified in a series of experimental studies. Experimental studies and numerical simulations were carried out for the process parameters: gas velocity 0.008, 0.012 and 0.016 m/s, gas temperature 550, 575, 600 and 625 °C, and catalyst mass 75, 100 and 125 g. The optimal process temperature was 575 °C, where the yield of isobutylene averaged 47.6% of the mass. As the temperature decreased, the yield of isobutylene decreased to 40.1% by weight on average. With an increase in temperature, the yield of isobutylene increased to 52.8% by weight on average, and the total yield of products of side reactions increased to 20% by weight on average. Changes in the gas velocity and catalyst mass had an insignificant effect on the values of the yield of isobutylene, but significantly affected the values of the yield of the by-products.

A comparative study of catalytic activity of nickel(II) complexes bearing 1,10-phenanthroline (phen) based ligands in homogeneous ethylene oligomerization process has been performed. It was found that activated by methylaluminoxane (MMAO-12), [NiBr2(phen)] complex oligomerizes ethylene with the moderate activity (66.2 x 10(3) mol(C2H4).mol(Ni)(-1).h(-1)) to the wide range (C4-C20) of even-numbered olefins, with a selectivity for linear alpha-olefins of 43%. The insertion of the carbonyl groups at the 5-and 6-position of 1,10-phenanthroline leads to an increase in catalytic activity up to 81.4 x 10(3) mol(C2H4).mol(Ni)(-1).h(-1). The presence of hydroxyl groups at the same positions causes a decrease in activity to 15.5 x 10(3) mol(C2H4).mol(Ni)(-1).h(-1). The steric hindrances near the metal center caused by the methyl groups at 2-and 9-position of 2,9-dimethyl-1,10-phenanthroline result in a decrease in the activity to (26.8-52.2) x 10(3) molC(2)H(4).molNi(-1).h(-1) and increasing of the selectivity to butenes to 80-96%. The use of activated by MMAO-12 organonickel sigma-complex [NiBr(Mes)(phen)] (where Mes = 2,4,6-trimethylphenyl) bearing Ni-C bond increases the oligomerization activity - the activated complex dimerizes ethylene to mainly butenes with activity of 83.5 x 10(3) mol(C2H4).mol(Ni)(-1).h(-1). At the same time, this sigma -complex in combination with Et3Al2Cl3 and EtAlCl2 served as activators exhibits higher oligomerization activity - (348.1-394.5) x 10(3 )molC(2)H(4).molNi(-1).h(-1), and lower selectivity to butenes - 58-61%.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Обобщены актуальные направления исследований в области металл-органических координационных полимеров (МОКП), проводимых в научных организациях и университетах России в последние 5—10 лет. Обзор охватывает вопросы дизайна, синтеза, топологического описания и прогнозирования свойств МОКП, разработки способов их химического конструирования и модификации, изучения современными физико-химическими методами, создания функциональных материалов на основе пористых каркасов (гетерогенных катализаторов, высокоэффективных и высокоселективных сорбентов нового поколения, проводящих материалов, систем для адресной доставки лекарств).

Quantum-chemical calculations were performed to rationalize the experimental molecular weight distribution of α-olefin products, revealing the main mechanistic models of the process.

The A g1 Raman spectral line was used for the determination of the stress distribution in the active component of chromia-alumina catalysts.

Current research fields of metal-organic frameworks (MOFs), which are being developed in the last 5-10 years by Russian scientific institutions and universities, are generalized. The review encompasses the design, synthesis, topological description, and prediction of MOF properties, the development of methods for their chemical engineering and modification, their investigation by modern physicochemical techniques, and the creation of functional materials based on porous frameworks (heterogeneous catalysts, highly efficient and highly selective sorbents of the new generation, conducting materials, systems for the target drug delivery).

The cationic polymerization of isobutylene and its block copolymerization with styrene using DiCumCl/TiCl4/2,6-lutidine initiating system has been studied in open conditions. It was shown that a higher concentration of proton trap is required in open conditions as compared to the glove box technique in order to have good control over molecular weight and polydispersity. Polyisobutylenes with Mn ≤ 50,000 g mol−1 and low polydispersity (Đ ≤ 1.2) were prepared at [Lu] = 12 mM. The synthesis of poly(styrene-block-isobutylene-block-styrene) triblock copolymer (SIBS) in open conditions required the addition of proton trap into two steps, half at the beginning of the reaction and the second half together with styrene. Following this protocol, a series of triblock copolymers with different length of central polyisobutylene block (from Mn = 20,000 g mol−1 to 50,000 g mol−1) and side polystyrene blocks (Mn = 4000 g mol−1–9000 g mol−1) with low polydispersity (Đ ≤ 1.25) were synthesized. High molecular SIBS (Mn > 50,000 g mol−1) with low polydispersity (Đ < 1.3) containing longer polystyrene blocks (Mn > 6000 g mol−1) demonstrated higher tensile strength (~13.5 MPa).

The nickel complexes ((PCN)-P-BzTz)NiX ((PC)-P-BzTz(H)N = 2-(3-((di-tert-butylphosphino)methyl)phenoxy)benzo[d] thiazole; X = F, Br) containing the unsymmetrical pincer k(3)-tridendate ligand with an oxo-bridged benzothiazole side-arm have been tested as homogeneous catalysts in ethylene oligomerization after preliminary activation by Modified Methylaluminoxane (MMAO). They showed high activity in the process (up to 200 x 10(3) mol C2H4 center dot molNi(-1).h(-1)), with formation of even-numbered olefins (mainly C-4-C-10 fractions) as products. The comparison of their performance with the results obtained for more rigid pyrazole-based analogues ((PCN)-P-Pyr)NiX ((PC)-P-Pyr(H)N = 1-[3-[(di-tert-butylphosphino)methyl]phenyl]-1H-pyrazole; X = F, Br) demonstrates a positive effect stemming from the increased ligand flexibility. Moreover, the activation of (BzTzPCN)NiX by MMAO was studied by UV-Vis and P-31 NMR spectroscopies combined with time-dependent density functional theory (TD-DFT), revealing the formation of Ni-CH3 species. Finally, DFT calculations were also performed to explore the mechanism of ethylene oligomerization catalyzed by the methyl analogues ((PCN)-P-Pyr)Ni(CH3) and ((PCN)-P-BzTz)Ni(CH3). (C) 2021 Elsevier B.V. All rights reserved.

Linear alpha-olefins are widely used in the petrochemical industry and the world demand for these compounds increases annually. At present, the main method for producing linear alpha-olefins is the homogeneous catalytic ethylene oligomerization. This review presents modern nickel catalysts for this process, mainly systems for obtaining of one of the most demanded oligomer-1-butene-which is used for the production of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE). The dependence of the catalytic performance on the composition and the structure of the used activated complexes, the electronic and coordination states of the nickel center was considered.

The electrochemical properties of cobalt(II), nickel(II), and iron(II) ions are studied by cyclic voltammetry in the presence of increasing amounts of 2,2'-bipyridine (bpy). It is shown that the addition of insignificant amounts of bpy (10–50 mol %) to solutions containing cobalt(II), nickel(II), and iron(II) ions leads to stabilization of the reduced metal(0) forms and prevents both their electrochemical deposition and the formation of unsoluble metal associates.

This paper addresses a review of platinum-based hydrosilylation catalysts. The main field of application of these catalysts is the curing of silicone polymers. Since the 1960s, this area has developed rapidly in connection with the emergence of new polymer compositions and new areas of application. Here we describe general mechanisms of the catalyst activity and the structural effects of the ligands on activity and stability of the catalysts together with the methods for their synthesis.

The reactivity of unsymmetrical pyrazole-based PCN pincer Ni(II) halides has been tested in the presence of copper(II) halides as an oxidizing agent as well as with NaBH4 and LiAIH(4) as a hydride source. While the reaction with CuX2 resulted into the generation of metastable PCN pincer Ni(III) species, the treatment of ((PCN)-P-tBu)NiCl with NaBH4 led to the preparation and isolation of the borohydride complex ((PCN)-P-tBu)Ni(BH4). Attempts to isolate nickel-hydride species upon treatment of ((PCN)-P-tBu)NiCl with either NaBH4 or LiAIH(4) invariably led to the formation of free PCN(H) ligand and metallic Ni(0) nanoparticles after an in situ reductive elimination from the (metastable) hydride derivative ((PCN)-P-tBu)NiH. Finally, the halide complexes (pre-activated by MMAO) have been tested as homogeneous catalysts in ethylene oligomerization showing moderate activity (similar to 14 x 10(3) mol(C2H4).mol(Ni)(-1).h(-1)) with the formation of even-numbered olefins (mainly C-4-C-10 fractions) as products. (C) 2020 Elsevier B.V. All rights reserved.

The catalytic activity of electrochemically synthesized zirconium carboxylates was studied in the process of ethylene oligomerization. Zirconium carboxylates were electrochemically synthesized directly from metallic zirconium and corresponding carboxylic acids (acetic, octanoic and lauric). A comprehensive study (element analysis, nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy, powder X-ray diffraction (PXRD)) of the synthesized zirconium carboxylates showed that these species contain bidentate carboxylate moieties. It was shown that obtained zirconium carboxylates, in combination with Et3Al2Cl3 (Al/Zr = 20), have a moderate activity of (7.6–9.9) × 103 molC2H4⋅molZr−1⋅h−1 in terms of ethylene oligomerization (at T = 80 °C, p = 20 bar), leading to even-numbered C4–C10 linear alpha-olefins.

α-Diphenylphosphino-N-(pyrazin-2-yl)glycine was synthesized by the three-component condensation of diphenylphosphine, glyoxylic acid hydrate, and 2-aminopyrazine and its structure was confirmed by X-ray diffraction. It reacted with [Ni(COD)2] (COD is cycloocta-1,5-diene) to give complexes that were tested as catalysts for selective dimerization/oligomerization of ethylene to but-1-ene (main product) and C6–C14 α-olefins, respectively.