Hynek Balcar

Rhenium Oxide Supported on Mesoporous Organised Alumina as a Catalyst for Metathesis of 1-Alkenes

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.

Hoveyda-Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15.

Summary 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.

Polybenzimidazole-supported [Rh(cod)Cl]2 complex: Effective catalyst for the polymerization of substituted acetylenes

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.

Poly(p-iodophenylacetylene): synthesis, characterization, polymer stability and photoelectrical properties

Abstract New functional acetylene, 1-ethynyl-4-iodobenzene, ( p -iodophenylacetylene) was prepared, characterized (i.r., n.m.r., u.v. and mass spectra) and transformed into high-molecular-weight polymers. Various WOCl 4 -based and MoCl 5 -based catalysts were used in the polymerization, the former leading to the red soluble and the latter to dark red insoluble poly( p -iodophenylacetylene) (PIPA), respectively. Both types of PIPA are non-crystalline and they differ in the configurational structure which, however, could not be assigned with certainty. A too high molecular weight and/or cross-linking is suggested as a reason of insolubility of PIPA prepared on Mo-based catalysts. The soluble PIPA was found to degrade autoxidatively in tetrahydrofuran solution at room temperature obeying the kinetic laws of polymer random degradation. The determined value of the rate constant of degradation, 2.6 × 10 −6 min −1 , is slightly higher than that found for unsubstituted poly(phenylacetylene) (PPA), under the same conditions. PIPA was found to possess a higher photo-conductivity than PPA at low and moderate electric fields. The Onsager model offers an adequate explanation for the measured dependence of the photogeneration efficiency of the applied electric field assuming the Gaussian distribution of the radii of charge-transfer states.

MCM-41-immobilized [Rh(cod)OCH3]2 complex: A hybrid catalyst for the polymerization of phenylacetylene and its ring-substituted derivatives

The immobilization of [Rh(cod)OCH 3 ] 2 (cod = cycloocta-1,5-diene) on mesoporous molecular sieves MCM-41 provides the first inorganic-type hybrid catalyst, which affords heterogeneous polymerization of phenylacethylene and its ring-substituted derivatives, - 2-fluorophenylacetylene, 4-fluorophenylacetylene, and 4-fluorophenylacetylene - into readily isolable high-molecular-weight (M w 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)OCH 3 ] 2 .

Polymerization of 4-(ferrocenylethynyl)phenylacetylene with transition metal catalysts

A new conjugated polymer carrying organometallic pendant groups, poly[4-(ferrocenylethynyl)phenylacetylene], has been prepared. [Rh(nbd)(OCH 3 )] 2 as a catalyst (nbd = norbornadiene) provides a mixture of an insoluble polymer (yield 71%) free of C≡CH groups and soluble oligomers (yield 22%, MW ca. 1100). WOCl 4 /2Me 4 Sn as a catalyst provides almost exclusively a polymer (yield 60%, M w = 32. 10 3 ) containing a small amount of C≡CH groups that is soluble in aromatic and low-polarity solvents. Its solubility, however, decreases upon storage in the solid state, probably due to a subsequent crosslinking. The 13 C NMR, IR, UV-vis and Raman spectra of the monomer and polymers are reported.

Polymerization of nitrophenyl propargyl ethers with transition metal catalysts and characterization of polymers

o-, m- and p-Nitrophenyl propargyl ethers were prepared, characterized (n.m.r., i.r.) and polymerized with tungsten and molybdenum based metathesis catalyst systems. Soluble high-molecular-weight (weight-average molecular weight about 4 × 105) poly(p-nitrophenyl propargyl ether)s were prepared in good yields using catalyst systems MoOCl4/Me4Sn and MoCl5/EtAlCl2. Insoluble poly(m-nitrophenyl propargyl ether)s and poly(o-nitrophenyl propargyl ether)s were prepared in moderate yields with the same catalyst systems. I.r. and n.m.r. spectra of all polymers confirmed polyacetylene type polymer structure with nitrophenoxymethyl pendant groups.

Polymerization of p-nitrophenylacetylene with metathesis catalysts. Photoelectrical properties of phenylacetylene/p-nitrophenylacetylene copolymer

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 WOCl 4 /3Me 4 Sn as a catalyst in benzene and benzene/dioxane as solvents. WOCl 4 alone does not polymerize, oligomerize and/or cyclotrimerize NPA. The two-component catalysts WOCl 4 /2Ph4Sn and MoOCl 4 /3Me 4 Sn 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 NO 2 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.

Characterization of textural and surface properties of mesoporous metathesis catalysis

Abstract Metathesis catalysts based on Re(VII)oxide supported on organized mesoporous alumina (OMA) were characterized by a number of experimental techniques including X-ray diffraction (XRD), X-ray photoelectron (XPS), FTIR spectroscopy, MAS NMR, and nitrogen isotherms to understand the changes in textural and chemical properties during the activation and the metathesis reaction of olefins. The presence of pentacoordinated Al, population of acidic OH groups, concentration of Lewis acid sites and reducibility of Re (VII) oxide to Re(IV) species in OMA based catalysts – there are the main features, which were discussed in connection with catalytic activity.

Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

Summary Hoveyda–Grubbs type catalysts with cationic tags on NHC ligands were linker-free immobilized on the surface of lamellar zeolitic supports (MCM-22, MCM-56, MCM-36) and on mesoporous molecular sieves SBA-15. The activity of prepared hybrid catalysts was tested in olefin metathesis reactions: the activity in ring-closing metathesis of citronellene and N,N-diallyltrifluoroacetamide decreased in the order of support MCM-22 ≈ MCM-56 > SBA-15 > MCM-36; the hybrid catalyst based on SBA-15 was found the most active in self-metathesis of methyl oleate. All catalysts were reusable and exhibited low Ru leaching (<1% of Ru content). XPS analysis revealed that during immobilization ion exchange between Hoveyda–Grubbs type catalyst and zeolitic support occurred in the case of Cl− counter anion; in contrast, PF6 − counter anion underwent partial decomposition.