Pavel V. Ivchenko

Controlled ring-opening polymerisation of cyclic phosphates, phosphonates and phosphoramidates catalysed by heteroleptic BHT-alkoxy magnesium complexes

We report here that the heteroleptic BHT-Mg(OR) complex, i.e. [(BHT)Mg(OBn)(THF)]2 (Mg3), represents an effective and versatile ring-opening polymerisation (ROP) catalyst for several cyclic ethylene phosphate monomers (CEPMs), such as ethylene phosphates with methoxy- (MeOEP, 1), isopropoxy- (iPrOEP, 2), and tert-butoxy- (tBuOEP, 3) substituents, N,N-diethyl ethylene phosphoramidate (Me2NEP, 4) as well as ethyl (EtPPn, 5) and tert-butyl (tBuPPn, 6) ethylene phosphonates. Mg3 retains its catalytic activity over a broad temperature range from −50 to 100 °C and efficiently carries out the fast and controlled polymerisation of CEPMs with sterically unhindered alkoxy groups with less than 1% chain branching even at near-complete conversion. Compared with ROP catalysed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), Mg3 performs much better in the polymerisation of CEPMs with bulky groups and of monomers sensitive to strong nucleophiles, such as tBuOEP.

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.

Synthesis of bis-cyclopentadienyl compounds with a 9,9-fluorenylidene bridge. Crystal and molecular structure of [μ-9,9-Flu(η5-Cp)2]ZrCl2

An efficient synthetic approach to 9,9-bis(cyclopentadienyl)fluorenes was developed. The two correspondingansa-zirconocenes were synthesized. The structure of one of these compounds was established by X-ray diffraction analysis.

Synthesis of 1-(cyclopentadienyl)adamantane and the corresponding zirconium complexes

An effective method for the synthesis of 1-(cyclopentadienyl)adamantane based on the reaction of 1-bromoadamantane with nickelocene in the presence of PPh3 was proposed. A number of organic derivatives and bis-cyclopentadienyl complexes of zirconium(iv) were prepared from this compound.

Molecular structure of ansa-compound (η5-C5H4)CMe2(η5-C9H6)TiCl2

The structure of a new ansa compound, (η5-C5H4)CMe2(η5-C9H6)TiCl2 (1), was studied by X-ray analysis:a = 15.00(1),b =15.500(5),c = 13.032(4) Å, β = 92.66°(4),V = 3025.1(1) Å3, space groupP21/α.,R = 0.038. The distorted tetrahedral coordination sphere of the Ti atom is formed by two Cl atoms and two π-ligands. It was proposed that the angle (τ) between theC-M direction and the line normal to M-Cp can be considered as one of the geometric parameters characteristic of the “structure-properties” correlation.

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.

Polymerization of trimethylene carbonate and lactones in the presence of magnesium monoionolate: A comparative theoretical and experimental study

Using quantum-chemical calculations (DFT, program Priroda), the formation of a catalyst species on the basis of magnesium complexes with 2,6-di-tert-butyl-4-methylphenol is discussed. A comparative theoretical and experimental study of the ring-opening polymerization of trimethylene carbonate, 1,4-dioxanone, δ-valerolactone, and e-caprolactone in the presence of the monoionolate magnesium complex is performed. It is shown that the calculated values of activation barriers correlate with the observed order of activity of cyclic esters. The maximum rate of polymerization is exhibited by trimethylene carbonate.

Titanium–magnesium nanocatalysts of polymerization (Review)

This review addresses the history of the development, structure, properties, and application prospects for a new class of ultrafine catalysts of coordination polymerization, viz., titanium–magnesium nanocatalysts.

Reactions of cyclopentadienes with phorone

Reactions of different cyclopentadienes with phorone were studied. Nonsubstituted and monosubstituted cyclopentadienes form annelation products,viz., 4,4,8,8-tetramethyl-1, 3a,4,5,6,7,8,8a-octahydroazulen-6-ones.

Polyolefin drag reducing agents (Review)

Main methods for the polymerization of higher α-olefins (1-hexene, 1-octene, and 1-decene) with the formation of high molecular weight products, key properties of poly-α-olefins from the viewpoint of their use as drag reducing agents in the transportation of petroleum and petroleum products, as well as the challenges and prospects of the production of these important functional materials of the petroleum industry have been considered.