Novel polymer-supported β-diketonate nickel catalysts for α-olefin activation

Styrene–divinylbenzene resins were used for the synthesis of different polymer-bound β-diketones, obtained by anchoring the chelating group through either the central or the lateral position. The heterogenized diketone ligand was subsequently reacted with Ni(COD)₂ analogously to the corresponding homogeneous catalysts active in α-olefin oligomerization. The heterogenized catalysts showed a good activity only when the central position of the chelate moiety was free. Heterogenization caused a significant change of selectivity: olefin oligomerization was accompanied by the formation of a large amount of polymeric products. This behavior is discussed in terms of steric effects caused by the bulky polymeric ligand. © 1998 John Wiley & Sons, Ltd.     

Radiation-induced terpolymerization of methyl α,β,β-trifluoroacrylate with tetrafluoroethylene and α-olefin

Radiation-induced terpolymerizations of methyl α,β,β-trifluoroacrylate (MTFA) with tetrafluoroethylene (TFE) and α-olefins, such as ethylene, propylene, and isobutylene, were carried out in bulk at 25°C for the purpose of controlling the content of ester group in the MTFA-α-olefin alternating copolymers. These monomers polymerized to form alternating terpolymers which contained 50 mole % α-olefin in a wide range of monomer composition. The content of MTFA, namely, the ester group in polymer, can be varied without destruction of the alternating structures between fluoroolefins (MTFA, TFE) and α-olefin by changing the MTFA/TFE ratio in the monomer mixture. The relative reactivities of MTFA and TFE in the terpolymerization were discussed according to kinetic treatments by free propagating and complex mechanisms. The relation between the MTFA/TFE ratio in the monomer mixture and that in terpolymer was explained favourbly by the complex mechanism. It was also concluded that the relative reactivity of MTFA is larger than that of TFE in the terpolymerizations.     

Proton magnetic resonance investigation of structure of ω-alkyl-α-olefin/SO2 copolymers

The 100 MHz proton magnetic resonance (PMR) spectra of free radical alternating ω-alkyl-α-olefin/SO₂ copolymers has been investigated. The data obtained from the quantitative evaluation of the spectra are consistent with a copolymer structure containing unrearranged olefinic monomer units. The 4-methyl-1-pentene/SO₂ copolymer shows a quadruplet resonance in the CH₃ proton region. This multiplicity, observed also in the analogous 1,2-dichloro-4-methylpentane and 1,2-dibromo-4-methylpentane, arises from the presence of magnetically nonequivalent CH₃ protons located in the vicinity of the asymmetric carbon atoms of the main chain. There is no detectable nonequivalency of CH₃ protons in the 5-methyl-1-hexene/SO₂ copolymer, probably because the center of asymmetry is further removed from the isopropyl group. In poly-4-methyl-1-pentene, prepared with Ziegler-Natta catalyst, the polymer structure around the main chain tertiary carbons is fairly symmetrical; and, as expected, the CH₃ protons of the isopropyl group are magnetically equivalent.     

Structure-activity and structure-selectivity correlations in metallocene-based catalysts for α-olefin polymerization

Zirconocene complexes carrying substituents at various positions of their ring-bridged ligand frameworks were studied as catalysts for methylalumoxane-activated propene polymerization. Effects of different substitution patterns on catalyst activities and on chain lengths and stereo- and regio-regularities of the polymers produced are correlated with geometrical features of the complexes, e.g. with parameters describing their structural rigidity or the aperture and obliquity of their coordination gaps.     

Ionization of MgCl2 during the formation of α-olefin polymeryzation catalyst

The examination of the reaction between [MgCl₂(THF)₂], TiCl₄₍₃₎, AlCl₃, AlEt₃, AlEt₂Cl and the synthesis and isolation of compounds as crystals and resolution of their structure by the X-ray method were the subject of our study. It was expected that these investigations would help to understand the behaviour of MgCl₂ towards the transition metal and furnish useful relationships to the structure of catalyst active center and to the polymerization mechanism in TiCl₄₍₃₎/MgCl₂/AlEt₃ system. Our studies have revealed that the main difference between the first and higher generations of Ziegler-Natta catalysts is only the number of active centers.     

A novel synthesis of α-hydroxy- and α,α′-dihydroxyketone from α-iodo and α,α′-diiodo ketone using photoirradiation

A novel reaction of α-iodo ketone (α-iodocycloalkanone, α-iodo-β-alkoxy ester, and α-iodoacyclicketone) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketone in good yields. In the case of α,α′-diiodo ketone, α,α′-dihydroxyketone which little has been reported until now was obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′-dihydroxyketone.     

Some newer concepts on ethylene/α-olefin copolymerization on heterogeneous Ziegler-Natta catalysts

Unsteady diffusion kinetics, recently advanced by this laboratory, is applied to the examination of some polymerization and molecular chain structure problems. Hitherto deemed “anomalous” phenomena, such as the faster rate of copolymerization of ethylene/α-olefin than the homopolymerization of ethylene and the enrichment in the incorporation of a higher α-olefin in its copolymerization with ethylene by a lower α-olefin, are reasonably explained by unsteady diffusion of monomers. Molecular chain structure of copolymers, such as compositional heterogeneity and its dependence on comonomer incorporation originates from the difference in diffusion coefficients of the monomers. A copolymer composition equation taking into consideration the unsteady diffusion was developed. In cases where simulated curves were compared with experimental curves, good agreements were found.