-
[show abstract]
[hide abstract]
ABSTRACT: New hybrid catalysts for olefin metathesis were prepared by immobilization of Hoveyda–Grubbs type Ru alkylidenes on a siliceous
SBA-15 support via exchange of chloro ligands for substituted carboxylates. Catalysts proved a high activity in ring closing
metathesis of 1,7-octadiene and diethyl diallylmalonate, reusability and low Ru leaching. In Ring Opening Metathesis Polymerization
of norbornene and cyclooctene, SBA-15 supported catalyst gave higher yields of high-molecular-weight polymers than corresponding
catalyst with conventional silica support.
KeywordsRing closing metathesis-Ring opening metathesis polymerization-Hybrid catalysts-Ru catalysts-SBA-15
Topics in Catalysis 04/2012; 53(3):200-209. · 2.62 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Microporous organic polymers (MOP) of a new type have been synthesised in high yields by a simple coordination polymerization of 1,3-diethynylbenzene, 1,4-diethynylbenzene and 4,4'-diethynylbiphenyl catalysed by [Rh(cod)acac] and [Rh(nbd)acac] complexes. The new MOPs are non-swellable polyacetylene-type conjugated networks consisting of ethynylaryl-substituted polyene main chains that are crosslinked by arylene linkers. Prepared MOP samples have a mole fraction of branching units (by (13) C CP/MAS NMR) from 0.30 to 0.47 and exhibit the BET (Brunaer-Emmett-Teller) surface up to 809 m(2) g(-1) and hydrogen uptake up to 0.69 wt% (77 K, H(2) pressure 750 torr).
Macromolecular Rapid Communications 11/2011; · 4.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A commercially available Hoveyda-Grubbs type catalyst (RC303 Zhannan Pharma) was immobilized on mesoporous molecular sieves MCM-41 and on SBA-15 by direct interaction with the sieve wall surface. The immobilized catalysts exhibited high activity and nearly 100% selectivity in several types of alkene metathesis reactions. Ru leaching was found to depend on the substrate and solvent used (the lowest leaching was found for ring-closing metathesis of 1,7-octadiene in cyclohexane - 0.04% of catalyst Ru content). Results of XPS, UV-vis and NMR spectroscopy showed that at least 76% of the Ru content was bound to the support surface non-covalently and could be removed from the catalyst by washing with THF.
Beilstein Journal of Organic Chemistry 01/2011; 7:22-8. · 2.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Siliceous mesoporous molecular sieves MCM-41, MCM-48 and SBA-15 and organised mesoporous alumina represent progressive supports for new heterogeneous catalysts for olefin metathesis and metathesis polymerization. In combination with Mo and Re oxides they provide catalysts of considerably higher activity in comparison with those based on conventional silica and alumina. Immobilization of Mo and Ru alkylidenes on these materials led to the highly active and selective catalysts with negligible leaching of transition metal.
Macromolecular Symposia 07/2010; 293(1):43 - 47.
-
[show abstract]
[hide abstract]
ABSTRACT: Heterogeneous catalysts for olefin metathesis using different types of (i) siliceous mesoporous molecular sieves, and (ii)
organized mesoporous alumina as supports are reported. The catalysts were prepared either by spreading of transition metal
oxidic phase on the support surface or by immobilizing transition metal compounds (mostly organometallic) on the support.
The activity of these catalysts in various types of metathesis reactions (i.e. alkene and diene metathesis, metathesis of
unsaturated esters and ethers, RCM, ROMP and metathesis polymerization of alkynes) was described. The main advantages of these
catalysts consist generally in their high activity and selectivity, easy separation of catalysts from reaction products and
the preparation of products free of catalyst residue. The examples of pore size influence on the selectivity in metathesis
reactions are also given.
12/2009: pages 101-114;
-
Journal of Polymer Science Part A Polymer Chemistry 03/2008; 46(8):2776 - 2787. · 3.92 Impact Factor
-
Journal of Polymer Science Part A Polymer Chemistry 02/2008; 46(7):2593 - 2599. · 3.92 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: New type of heterogeneous catalyst for metathesis of linear 1-olefins based on rhenium (VII) oxide supported on organized mesoporous alumina was developed. This catalyst operates under very mild reaction conditions without any solvent and the highest activity was achieved at the reaction temperature of 60 C with selectivity to symmetrical olefin over 90%. The optimum loading of rhenium (VII) oxide was found to be between 9 and 15 wt% of Re. The initial activity was dependent on pore size diameter—the larger pore diameter, the higher initial catalytic activity under the same reaction conditions.
Catalysis Letters 07/2004; 97(1):25-29. · 2.24 Impact Factor
-
Macromolecular Rapid Communications 03/2003; 15(10):771 - 776. · 4.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The first heterogeneous catalyst which affords polymerization of substituted acetylenes into readily available high molecular weight polymers is reported. The catalyst (Rh/PBI) has been prepared by supporting di-mu-chloro-bis(eta4-cycloocta-1,5-diene)dirhodium(I), [Rh(cod)Cl]2, on commercial polybenzimidazole (PBI) porous beads by means of a simple quantitative adsorption from THF solution, and tested in polymerization of phenylacetylene, 4-fluorophenylacetylene, and 4-pentylphenylacetylene. The polymer molecules formed were found to be released from the Rh/PBI to surrounding solution during the polymerization performed in THF. Formation of high molecular weight ((M)w values up to 325,000) polymers in prevailing cis-transoid configuration has been observed with all monomers. In a comparison with free [Rh(cod)Cl]2 used as the homogeneous catalyst, the Rh/PBI can be used repeatedly, exhibits somewhat lower polymerization activity but almost no oligomerization activity, and provides polymers of higher molecular weight.
Chemistry 02/2002; 8(2):366-71. · 5.93 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The immobilization of [Rh(cod)OCH3]2 (cod = cycloocta-1,5-diene) on mesoporous molecular sieves MCM-41 provides the first inorganic-type hybrid catalyst, which affords heterogeneous polymerization of phenylacetylene and its ring-substituted derivatives, – 2-fluorophenylacetylene, 4-fluorophenylacetylene, and 4-pentylphenylacetylene – into readily isolable high-molecular-weight (M̄w from 50 000 to 180 000) substituted polyvinylenes of high cis-transoid structure. The activity of this catalyst is compared with that of homogeneous catalyst [Rh(cod)OCH3]2.
Macromolecular Rapid Communications 01/2002; 23(1):32 - 37. · 4.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: N-Benzylidene-4-ethynylanilines, R—C6H4—CH=N—C6H4—C≡CH substituted in 4′ position by R = H, t-Bu, F, Br, CN, NO2 and Me2N, were polymerized in tetrahydrofuran using [Rh(cod)X]2 (cod = 1,5-cyclooctadiene; X = Cl, OCH3) as a catalyst to result in polyacetylene type polymers. Monomers with R = H, t-Bu and F gave tetrahydrofuran-soluble polymers of molecular weights Mw from 15 000 to 100 000; monomers with Br, CN, NO2 and Me2N as substituents gave polymers insoluble in tetrahydrofuran and other common organic solvents. The polymer structure, consisting of conjugated polyene main chain and 4-(N-benzylideneamino)phenyl pendant groups, was confirmed by IR, UV-vis and NMR spectroscopy.
Macromolecular Chemistry and Physics 11/1999; 200(12):2591 - 2596. · 2.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Preparation of substituted acetylene polymers carrying nitro group is reported for the first time. Homopolymers of p-nitrophenylacetylene (NPA) and its copolymer with phenylacetylene (PA) have been prepared by polymerizations induced by WOCl4/3 Me4Sn as a catalyst in benzene and benzene/dioxane as solvents. WOCl4 alone does not polymerize, oligomerize and/or cyclotrimerize NPA. The two-component catalysts WOCl4/2Ph4Sn and MoOCl4/3Me4Sn produce low amounts of oligomers only. The homopolymer of NPA is insoluble, whereas the copolymer containing one NPA unit per 4.38 units of PA is soluble in aromatic solvents and THF. The IR and NMR spectra of the homopolymer and the IR spectrum of the copolymer are reported. The photoconductive properties of the copolymer are also reported and compared with those of poly(PA). Introduction of NO2 groups onto polymer chains was found to increase the quantum efficiency of charge carrier photogeneration but to deteriorate the charge carrier transport properties of the polymer.
Macromolecular Chemistry and Physics 12/1998; 199(1):155 - 161. · 2.36 Impact Factor
-
Journal of Molecular Catalysis A Chemical 332:19-24. · 2.95 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Catalytic activity of the tungsten aryloxo complexes WCl<sub>5</sub>(OAr) and WOCl<sub>3</sub>(OAr), where Ar = 4- t -C<sub>4</sub>H<sub>9</sub>C<sub>6</sub>H<sub>4</sub>, 2,6-( t -C<sub>4</sub>H<sub>9</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, 2,6-Cl<sub>2</sub>C<sub>6</sub>H<sub>3</sub>, 2,4,6-Cl<sub>3</sub>C<sub>6</sub>H<sub>2</sub>, and 2,4,6-Br<sub>3</sub>C<sub>6</sub>H<sub>2</sub> in polymerization of phenylacetylene (20 °C, monomer to catalyst molar ratio = 1 000) was studied. The activity of WCl<sub>5</sub>(OAr) as unicomponent catalysts increases with increasing electron withdrawing character of the -OAr ligand. Addition of two equivalents of organotin cocatalysts (Me<sub>4</sub>Sn, Bu<sub>4</sub>Sn, Ph<sub>4</sub>Sn, Bu<sub>3</sub>SnH) to WCl<sub>5</sub>(O-C<sub>6</sub>H<sub>2</sub>Cl<sub>3</sub>-2,4 ,6) has only slight positive effect (slightly higher polymer yield and/or molecular weight of poly(phenylacetylene)s was achieved). However, in the case of WOCl<sub>3</sub>(O-C<sub>6</sub>H<sub>3</sub>Cl<sub>2</sub>-2, 6) catalyst, it enhances the activity considerably by eliminating the induction period. Poly(phenylacetylene)s prepared with the catalysts studied have weight-average molecular weight ranging from 100 000 to 200 000. They are trans -prevailing and have relatively low molar fraction of monomer units comprised in cyclohexadiene sequences (about 6%).
-
[show abstract]
[hide abstract]
ABSTRACT: Reaction between WCl<sub>6 </sub>and norbornene in benzene and cyclohexane, respectively, was investigated using UV/VIS, ESR and XPS spectroscopy in order to establish the main reaction products on the tungsten side and their relation to the initiation of ring opening metathesis polymerization (ROMP) of norbornene. The tungsten compounds: WCl<sub>5</sub>, insoluble WCl<sub>4 </sub>and soluble tungsten species having four chlorine atoms bound to tungsten, [WCl<sub>4</sub>L<sub> n </sub>] were found to be the main products. The catalytic activity of the respective compounds in ROMP of norbornene was found to decrease in the order: WCl<sub>5 </sub>> WCl<sub>6 </sub>>> WCl<sub>4</sub> ~ [WCl<sub>4</sub>L<sub> n </sub>]. The polynorbornenes prepared with both WCl<sub>4 </sub>and [WCl<sub>4</sub>L<sub> n </sub>] possess higher content of cis double bonds in comparison with polymers prepared with WCl<sub>6 </sub>and WCl<sub>5 </sub>catalysts.
-
[show abstract]
[hide abstract]
ABSTRACT: 2-, 3- and 4-Nitrophenyl prop-2-yn-1-yl ethers were polymerized with PdCl<sub>2</sub> in N , N -dimethylformamide (DMF) giving brown polymers soluble in DMF, dimethyl sulfoxide and N -methylpyrrolidone. Broad (mostly bimodal) molecular weight distributions were observed by size-exclusion chromatography (SEC) with maxima at molecular weight of about 4 . 10<sup>3</sup> and 1 . 10<sup>5</sup>. With the same catalyst, 3-diethylaminophenyl prop-2-yn-1-yl ether gave predominantly low molecular weight homopolymer ( M<sub>n</sub> = 4 200) soluble in DMF, N -methylpyrrolidone, CHCl<sub>3</sub> and tetrahydrofuran-soluble copolymers with 4-nitrophenyl prop-2-yn-1-yl ether ( M<sub>n</sub> about 3 000). IR, NMR and UV-VIS spectra of prepared polymers and copolymers proved the structure to consist of the polyene-type main chain with phenoxymethyl pendant groups bearing nitro or diethylamino substituents.
-
[show abstract]
[hide abstract]
ABSTRACT: 2-, 3- and 4-Iodophenylacetylenes (IPA) have been polymerized with [Rh(cod)(OCH<sub>3</sub>)]<sub>2</sub> complex in THF (system Rh), MoCl<sub>5</sub> in benzene (Mo), WOCl<sub>4</sub> in benzene (WB) and WOCl<sub>4</sub>/Ph<sub>4</sub>Sn in benzene-dioxane 1 : 1 (WD). All the systems provide poly(iodophenylacetylene)s (PIPA) and diverse amounts of oligomers (mostly cyclic trimers and tetramers) but the system 2-IPA/Rh that provides mostly dimers only. 2-IPA has also been polymerized with MoOCl<sub>4</sub>/Bu<sub>4</sub>Sn/EtOH in toluene (Masuda's catalyst system), however, neither living nor pseudo-living polymerization has been observed. The ring-iodine steric effects control the polymerization activity of the Rh and WB systems and the oligomerization activity of the Mo system. The ring-iodine electronic effects are important for the oligomerization activity of the Rh and WB systems and both oligomerization and polymerization activity of the WD system. Both types of the ring-iodine effect are important for polymerization activity of the Mo system. Rh catalyst provides high- cis -transoid, head-to-tail (HT) 3-PIPA that slowly isomerizes in CDCl<sub>3</sub> solution to an insoluble trans-polymer. In the case of 4-PIPA, the isomerization is extremely fast upon polymer entering into contact with methanol. On the basis of spectral changes accompanying this isomerization, the Raman band at 1 338 cm<sup>-1</sup> is assigned to the presence of HT sequences of both cis -transoid and trans -cisoid type. The other catalysts provide irregular PIPAs with content of both cis units and HT sequences decreasing in order Mo > WD > WB. Solubility of PIPA samples is shown as a result of complex interplay of the ring-iodine position and the polymer microstructure and molecular weight.
-
[show abstract]
[hide abstract]
ABSTRACT: 4-Substituted N -(4-ethynylbenzylidene)anilines (4-HC≡C-C<sub>6</sub>H<sub>4</sub>-CH=N-C<sub>6</sub>H<sub>4</sub>-4-R; R = Me, t -Bu, OMe, F, Cl, Br, I, CF<sub>3</sub> and NO<sub>2</sub>) have been prepared by condensation of 4-ethynylbenzaldehyde with appropriate anilines under mild conditions in good yields. The products obtained were fully characterized by GC-MS, IR, NMR and UV-VIS spectroscopies and their properties were compared with a series of 4-ethynyl- N -(4-substituted benzylidene)anilines (4-HC≡C-C<sub>6</sub>H<sub>4</sub>-N=CH-C<sub>6</sub>H<sub>4</sub>-4-R; R = H, Me, t -Bu, F, Br, NO<sub>2</sub>, CN, NMe<sub>2</sub>). The influence of substituent R on spectroscopic characteristics is discussed.
-
[show abstract]
[hide abstract]
ABSTRACT: Hybrid catalysts for polymerization of acetylenes were prepared by anchoring, via (3-aminopropyl)trimethoxysilane linker, the [Rh(cod)Cl]<sub>2</sub> complex on siliceous mesoporous molecular sieves differing in the pore size and architecture (MCM-41, MCM-48 and SBA-15). In comparison with [Rh(cod)Cl]<sub>2</sub> used as homogeneous catalyst, all hybrid catalysts exhibited comparable or even higher catalytic activity in the polymerization of phenylacetylene and 4-ethynyl- N -{4-[(trimethylsilyl)ethynyl]benzylidene}aniline. The initial polymerization rate increased with increasing accessibility of mesoporous surface of catalysts in the order: MCM-41 < MCM-48 < SBA-15. Molecular weights of the prepared polymers increased in reverse order suggesting suppression of the chain growth termination reactions by space limitations in the pores. No effect of catalyst support on the microstructure of formed polymers was found.
