Alexander N. Tavtorkin

Synthesis and gas-separation properties of metathesis poly(3-fluoro-3-pentafluoroethyl-4,4-bis(trifluoromethyl)tricyclonene-7)

Metathesis polymerization of 3-fluoro-3-pentafluoroethyl-4,4-bis(trifluoromethyl)tricyclononene-7 (F-PTCN) and the properties of the resulting polymer, particularly gas permeability, have been studied. It has been found that F-PTCN exhibits high thermal stability. The gas separation parameters of the material (P(O2) = 60 Barrer, P(CO2) = 240 Barrer) are close to those of fluorinated polynorbornenes studied previously. The newly synthesized fluorinated metathesis polytricyclononene has a lower gas permeability than metathesis polytricyclononene bearing two Me3Si groups in the monomer unit, but it is significantly superior to the latter in gas separation selectivity for some gas pairs.

Modified titanium-magnesium nanocatalysts in the polymerization of isoprene

The polymerization of isoprene on titanium-magnesium nanocatalysts modified with electron-donor compounds based on organic phosphines and sulfides has been studied. It was shown that the catalyst modification makes it possible to increase the content of trans-1,4 units in polyisoprene up to 97% (according to the data of 1H NMR spectra). In the case of a catalyst modified with tributylphosphine, the effects of the phosphorus-to-titanium ratio on the polymerization kinetics, on the microstructure of trans-1,4-polyisoprene, and on the molecular mass of the polymer have been estimated.

Branched alkylphosphinic and disubstituted phosphinic and phosphonic acids: effective synthesis based on α-olefin dimers and applications in lanthanide extraction and separation

A number of mono-alkylphosphinic acids RCH2CH2CH(R)CH2P(O)(H)OH 8–12 were obtained via interaction of α-olefin vinylidene dimers RCH2CH2C(R)CH2 3–7 (R = n-butyl, 3, 8; isobutyl, 4, 9; n-octyl, 5, 10; isopropyl, 6, 11; cyclohexyl, 7, 12) with H3PO2 in an isopropanol medium at 90 °C. Hydrophosphinylation of 3 by 8 or PhPO2H2 at 140 °C resulted in disubstituted acids 13 and 14. Alkyl-methylphosphinic acids 15–19 and functionalized alkylphosphinic acids 20–22 have been synthesized via interaction of silyl ethers of mono-alkylphosphinic acids 8–12 with MeI, (2-chloromethyl)pyridine, acrylic acid or acrylamide. Non-catalytic hydroalumination of 3 with subsequent interaction with PCl3 and oxidation with SO2Cl2 led to the phosphonic acid anhydride, which was further used to obtain alkylphosphonic acids 23 and 24. It has been found that phosphinic acids 8–12 surpass di(2-ethylhexyl)phosphoric acid (extractant P204) in non-selective Ln3+ extractability (Ln = La, Pr, Nd, Dy and Lu). Significantly higher selectivity for heavy lanthanide extraction (Ln = Dy, Lu), compared to that of P204, is achieved by using a minimal excess of disubstituted phosphinic acids 13–24. Acid 13, which contains two branched substituents, demonstrated unique selectivity in the extraction of Lu in the presence of the other lanthanides. Dialkylphosphinic acids 16–18 and alkylarylphosphinic acid 14 possess a significant potential for the Pr/Nd pair separation. Taking into account the availability of 8–24 and the structural variability of the initial α-olefin dimers 3–7, the newly obtained compounds represent a promising group of rare-earth element extractants.

Crystal structure of [bis-(2,6-diiso-propyl-phen-yl) phosphato-κO]tris-(methanol-κO)lithium methanol monosolvate.

In the first reported crystal structure of the family of lithium phosphate diesters, the Li atom is in a slightly distorted tetrahedral coordination environment and exhibits one intramolecular O—H⋯O hydrogen bond between a coordinating methanol molecule and the terminal non-coordinating O atom of the phosphate group. The unit is connected with two non-coordinating methanol molecules through two intermolecular O—H⋯O hydrogen bonds and with a neighbouring unit through two other O—H⋯O interactions.

Non-traditional Ziegler-Natta catalysis in a-olefin transformations: reaction mechanisms and product design

Abstract This paper describes our recent results in the field of zirconocene-catalyzed α-oltfin transformations, and focuses on questions regarding the reaction mechanism, rational design of zirconocene pre-catalysts, as well as prospective uses of α-olefin products. It has been determined that a wide range of α-olefin-based products, namely vinylidene dimers, oligomers and polymers, can be prepared via catalysis by zirconocene dichlorides, activated by a minimal (10–20 eq.) amount of MAO. We assumed that in the presence of minimal quantities of MAO, various types of zirconocene catalysts form different types of catalytic particles. In the case of bis-cyclopentadienyl complexes, the reactive center is formed under the influence of R2AlCl, which makes the chain termination via β-hydride elimination significantly easier, with α-olefin dimers being formed as the primary product. Bis-indenyl complexes and their heteroanalogues, form stable cationic catalytic particles and effectively catalyze the polymerization. Mono-indenyl and mono-substituted bis-cyclopentadienyl-ansa complexes catalyze α-olefin oligomerization. Effective catalysts of dimerization, oligomerization and polymerization of α-olefins in the presence of minimal MAO quantities are proposed. Prospects of using α-olefin dimers, oligomers and polymers in the synthesis of branched hydrocarbon functional derivatives (dimers), high quality, low viscosity motor oils (oligomers), and thickeners and absorbents (polymers) are examined.

Influence of the synthesis conditions on the structure and composition of the titanium–magnesium nanocatalyst and on its activity in isoprene polymerization

Synthesis of titanium–magnesium nanocatalyst in a high-pressure reactor under the conditions modeling the industrial conditions was studied. A laboratory scale plant including the units for the product synthesis, washing, and filtration was developed. The effect of elevated pressure (10–90 atm) on the process course, on the properties of the catalyst formed, and on the isoprene polymerization was studied for the first time. An increase in pressure leads to an increase in titanium incorporation into the catalyst from 1.52 to 2–2.3 wt % and simultaneously to an increase in the trivalent titanium content to 81 wt %. The titanium–magnesium nanocatalyst with such properties exhibits enhanced performance in isoprene polymerization without deteriorating the polymer microstructure. The development of the catalyst synthesis procedure on the laboratory scale plant will allow pilot-scale modeling of this process in the future.

Steric and electronic factors in the promoting activity of diphosphine ligands in cyclohexene hydrocarbomethoxylation catalyzed by palladium acetate

Cyclohexene hydrocarbomethoxylation catalyzed by Pd(OAc)2-p-toluenesulfonic acid-diphosphine systems has been investigated for a wide range of diphosphine structures and concentrations. The factors controlling the activity of the palladium-containing catalysts include the hydrocarbon moiety of the ligand and the mutual arrangement of the phosphine groups. A comparison between the promoting effects of monophosphine and diphosphine ligands has demonstrated that bridged trans-diphosphines are more efficient in kinetic and concentration terms (TOF and P/Pd ratio, respectively). In particular, the promoting activity of diphosphines is one order of magnitude higher than that of triphenylphosphine, and this effect is attained at 8–65 times lower P/Pd ratios. It is discussed how the catalytic properties of the systems depend on the chelate effect and on the geometric compatibility between the diphosphine structure and the arrangement of vacant s and d orbitals of the palladium center.