M. V. Bermeshev

Titanium complexes based on chiral enantiopure dialkanolamines: synthesis, structures and catalytic activity

New chiral enantiopure tridentate ligands (dialkanolamines) RN(CHR3CR1R2OH)(CHR4CR5R6OH) 10–17 were synthesized by the opening of the epoxide ring by the action of the amines or alkanolamines. Titanium complexes, viz. [RN(CHR3CR1R2O)(CHR4CR5R6O)]Ti(O-i-Pr)218–23 and [RN(CHR3CR1R2O)(CHR4CR5R6O)]2Ti 25–31 were synthesized by treatment of Ti(O-i-Pr)4 with one or two equivalents of corresponding dialkanolamines. Complex (R)-PhCH(Me)N(CH2C(Me)2O)2TiCl2*HNMe224 was obtained from the reaction of one equivalent of dialkanolamine 10 with (Me2N)2TiCl2. The composition and structure of all novel compounds were established by 1H and 13C NMR spectroscopy as well as elemental analysis. The possible solution structures of 18–31 are discussed. The single-crystal X-ray diffraction study of 23, 25–28, 30, 31 indicates monomeric structures in the solid state. Chiral complexes 20, 22, 23, 25, 26, 30 were tested as chiral catalysts in the Abramov reaction and demonstrated moderate enantiomeric activity.

Highly permeable polymer materials based on silicon-substituted norbornenes

An approach to the manufacture of highly permeable polymers based on the synthesis and polymerization of norbornenes, norbornadienes, and tricyclononenes with different numbers and different positions of silicon-containing substituents has been developed. It has been found that these monomers are readily involved in metathesis polymerization yielding high-molecular-mass polymers possessing good filmforming properties. The addition (vinyl) polymerization of norbornenes is a more complex process; however, the product silylated polynorbornenes exhibit a higher gas permeability than the corresponding metathesis polynorbornenes. By the level of the gas-transport parameters, the silylated addition polynorbornenes obtained in the study are grouped with the most advanced high-permeability polymers. It has been shown that the presence of Me3Si substituent groups, their amount, and the main-chain structure are responsible for the enhancement of the gas permeability of polynorbornenes. Thus, a series of polymers with a regularly changing structure has been obtained, a result that makes it possible to reveal the polymer structure-property relations.

Synthesis and gas separation properties of metathesis polynorbornenes with different positions of one or two SiMe3 groups in a monomer unit

The metathesis polymerization of 5,5-bis(trimethylsilyl)norbornene, 2,3-bis(trimethylsilyl)norbornadiene, and exo,endo-3,4-bis(trimethylsilyl)tricyclo[4.2.1.02,5]non-7-ene with the catalysts WCl6/1,1,3,3-tetramethyl-1,3-disilacyclobutane, RuCl3/EtOH, and the Grubbs Ru-carbene complex Cl2(PCy3)2Ru=CHPh has been studied. New polymers with yields of up to 98% and M w = (2−39) × 105 are prepared. New metathesis copolymers of 5-trimethylsilylnorbonene with 5-(hydroxymethyl)norbornene and 5-(trimethylsiloxymethyl)norbornene are synthesized in the presence of the Cl2(PCy3)2Ru=CHPh catalyst with yields of 78 and 98%. The gas-permeability study of the above series of the metathesis polymers containing one or two Me3Si substituents in each monomer unit shows that the introduction of the second SiMe3 group markedly improves their transport characteristics. A change in the character of the backbone (polynorbornadiene, polytricyclononene) has a small effect on the permeability of the polymers. The metathesis polynorbornene with two vicinal SiMe3 groups exhibits higher gas-permeability coefficients than its isomer with germinal substituents. The homopolymer of 5-trimethylsilylnorbornene is characterized by better transport parameters than its copolymers with -OSiMe3 and -OH substituents.

New quadricyclane-based cyclic polycarbosilanes

49 Previously, we showed that silicon-substituted norbornenes and norbornadienes can be widely used for synthesizing macromolecular structures with regularly changed substituents with the aim of revealing theoretically and practically important structure– property relationships [1]. It turned out that polynorbornenes containing trimethylsilyl side groups have good gas transport properties and can serve as efficient membrane materials [2]. We showed that it is precisely Me 3 Si substituents that are responsible for the gas-separation properties and an increase in their number in the monomeric unit enhances the permeability coefficients of polymers. When studying the synthesis of polycarbosilanes of this type, we demonstrated that norbornene and norbornadiene with two SiMe 3 substituents, being active monomers in metathesis polymerization, are almost not polymerized by the addition (vinyl) scheme (Scheme 1). An analogous problem for fluoro-substituted norbornenes was described in [3]. Scheme 1. In the present paper, we describe a new efficient approach to the synthesis of Me 3 Si-substituted norbornenes capable of polymerizing not only by the metathesis mechanism but also by the addition one. This approach involves removal of bulky Me 3 Si substituents from the double bond responsible for polymerization due to the synthesis of 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0 2,5 ]non-7-ene. This compound was synthesized by a reaction that had not been described in organosilicon chemistry, namely, by the reaction of quadricyclane with the corresponding organochlorosilane, trans -1,2-bis(trichlorosilyl)ethylene, and subsequent methylation of the resulting chlorosilyltricyclononene (Scheme 2). Me3Si SiMe3

Comparative Reactivity of Me 3 Si-substituted Norbornene Derivatives in Ring-Opening Metathesis Polymerization

Silyl substituted norbornenes and their derivatives are effective monomers in the synthesis of new prospective polymer materials for gas separation membranes by metathesis and addition polymerization. Comparative activity of norbornenes (NB), norbornadienes (NBD) and tricyclononenes (TCN) with different spatial arrangement of one or two Me3Si substituents in ring-opening metathesis polymerization (ROMP) in the presence of Grubbs initiator Cl2(PCy3)2Ru =CHPh were studied by NMR and GC. It was shown that the rate of the initiation was lower than the propagation for all monomers and the highest activity was inherent to the exo-5-trimethylsilylnorbornene (5-NBSi) and 3-trimethylsilyltricyclononene (3-TCNSi). Disubstituted TCN turned out to be more active than NB having the same number and position of the substituents. The latter were more active than the corresponding NBD. It was found that syn- and anti-isomers of 3-TCNSi polymerized with close rates in contrast to exo- and endo-substituted 5-NBSi, for which polymerization rates were substantially different. Special behavior of monomers with bulky substituents in the geminal position was observed: 5,5-NBSi2 was inactive in the presence of the 1st generation Grubbs initiator, whereas it was polymerized in the presence of the 2nd generation one. Quantum-chemical calculations were in agreement with experimental data and evidenced the influence of energy, electronic and structural properties of the norbornene-type monomers studied on their activity in ROMP.

Copolymerization of 5-(trimethylsilyl)norbornene and 5-ethylidene-2-norbornene

Addition and metathesis copolymerization of 5-(trimethylsilyl)norbornene (TMSNB) and 5-ethylidene-2-norbornene (ENB) has been studied. High-molecular-weight metathesis copolymers have been obtained on the first-generation Grubbs catalyst based on the Ru carbene complex Cl2Ru(=CHPh)(PCy3)2 with nearly quantitative yields. Addition copolymerization has been carried out on the Ni(II) naphthenatemethylaluminoxane (MAO) catalytic system. In both cases copolymerization proceeded without participation of ethylidene double bond. Copolymers of this type are promising ones for manufacturing stable highly permeable polymeric membranes, since they are capable for crosslinking.

New stationary phases for gas chromatography based on polymers with intrinsic porosity

Norbornene polymers with intrinsic porosity were investigated as candidates for polymeric stationary phases in capillary GC. Kinetic and thermodynamic characteristics of the stationary phases were evaluated and turned out that only polymer with vicinal distribution of trimethylsilyl groups (polymer II) provided properties making it potential candidate for application in capillary GC. Columns with stationary phase based on polymer II demonstrated unique selectivity, moderate thermostability and efficiency better than previously studied columns with stationary phase based on poly[(1-trimethylsilyl)-1-propine].

Mobility of the spin probe TEMPO in glassy metathesis polymers with substituents containing flexible Si-O-Si groups

Glassy metathesis polymers (glass-transition temperatures of 110–236°C) containing substituents with flexible Si-O-Si groups are studied by the spin-probe method with the use of the stable nitroxyl radical TEMPO. A high mobility of the spin probe not correlating with the free volume of polymers is reported. These results and the earlier discovered thermodynamic selectivity of the indicated polymers (high permeability coefficients of higher hydrocarbons) make it possible to infer that Si-O-Si groups are responsible for the observed behavior similarly to that in siloxane rubbers.

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.

Synthesis and metathesis polymerization of 5,5-Bis(trimethylsilyl)norbornene-2

Abstract5,5-Bis(trimethylsilyl)norbornene-2 was synthesized in a yield of 60% via the scheme of diene condensation of cyclopentadiene with 1,1-bis(trimethylsilyl)ethylene and subsequent methylation of the resulting adduct with methyllithium. Its metathesis polymerization was first performed on W and Ru catalysts with yields of up to 98%. The structure of the new polymer was determined by means of the NMR and IR techniques. The tungsten catalyst makes it possible to prepare the polymer with a 40% amount of trans-double bonds, whereas the ruthenium catalyst is more selective and yields the polymer that contains almost 100% trans-double bonds. A high glass transition temperature as compared to other silicon-substituted metathesis polynorbornenes (196–203°C) indicates a high rigidity of the polymer chain and suggests that the polymer will have good gas-separation properties.