Polymerization of isoprene with vanadium-containing catalysts: Kinetic nonuniformity of active centers

For the polymerization of isoprene catalyzed by vanadium-based ion-coordination systems, the kinetic nonuniformity of active centers was studied and active centers of three to four types were revealed. By the solution of inverse kinetic problems, kinetic parameters were first estimated for individual active centers. It was demonstrated that the nature of an organoaluminum compound affects the kinetic nonuniformity of a catalyst, kinetic parameters of individual active centers, and molecular characteristics of polyisoprene.     

Polymerization of 1,3-dienes with neodymium catalysts

Neodymium catalysts are typical for the cis polymerization of 1,3-dienes. The systems prepared from a neodymium-carboxylate, a chlorine donor and A1(i-C₄H₉)₃ are characterized by a low efficiency, only ca. 6% of the neodymium being active in the catalysis. Much more active systems are obtained using allyl derivatives of neodymium in combination with aluminoxanes, in particular with methylaluminoxane (MAO). These systems have the characteristics of a single site catalyst. Evidence suggesting an ionic structure for the catalytic species is reported. Terminally substituted butadienes give polymers with a cis-1,4 isotactic structure, with the exception of (E, E)-2,4-hexadiene, which gives trans-1,4 polymers. An interpretation is reported.     

The dimerization of isoprene on complex nickel catalysts

Summary Eight-membered dimers, 1,5(1,6)-dimethylcyclooctadiene-l,5, were obtained as the main products by dimerizing isoprene on a complex nickel catalysts.     

Polymerization of acetylenes with rare earth coordination catalysts

The polymerization of acetylene and its derivatives by rare earth coordination catalysts and the characterization of the polymers so obtained in our laboratory are reviewed. Because of the metallic conductivity possessed by doped polyacetylene and the unique properties such as conductivity (semiconductivity), paramagnetism, migration and transfer of energy and chemical reactivity and complex formation ability often shown by acetylenic polymers, which seem promising as specialty polymers, there has been considerable interest in the polymers of acetylene and its derivatives. A wide variety of catalyst systems have been developed for the polymerization of acetylenes. But there has been no information concerning the use of rare earth compounds as catalysts in the polymerization of acetylene and its derivatives. We for the first time in 1981 have succeeded in the polymerization of acetylene with rare earth coordination catalysts, which in turn is a development based upon earlier work on the diene polymerization using rare earth coordination catalysts(Ref. 1). Using rare earth catalysts, acetylene can be polymerized conveniently into high cis polyacetylene films with metallic sheen at room temperature and phenylacetylene can also be polymerized into high molecular weight, high cis polyphenylacetylene films at ambient temperature. Thus new varieties of polyacetylenes have been developed and a novel family of coordination catalysts consisting of a rare earth compound plus trialkyl aluminum for the polymerization of acetylenes has been exploited. This article reviews our studies on the polymerization of acetylene and its derivatives with rare earth coordination catalysts and on the characterization of the polyacetylenes prepared.     

Polymerization of N-phenylmaleimide with rare earth coordination catalysts

A highly active rare earth coordination catalyst composed of neodymium acetylacetonate, dibutylmagnesium, and hexamethylphosphoramide (mole ratio 1:7:14) for the polymerization of N-phenylmaleimide (N-PMI) was developed. The resulting poly(N-PMI) has high molecular weight (M̄_n = 9.0 × 10⁴) and shows excellent thermal stability.     

Polymerization of isoprene catalyzed by neodymium heterocyclic Schiff base complex

Neodymium-based heterocyclic Schiff base complex was prepared and applied for the coordination polymerization of isoprene. This complex polymerized isoprene to afford products featuring high cis-1,4 stereospecificity （ca. 95%） and high molecular weight （ca, 10^5） in the presence of the triisobutyl aluminium （AliBu3） as cocatalyst, The microstructure of obtained polyisoprene was investigated by FTIR, 1^H NMR. Two different kinds of active centers in the catalyst system were examined by GPC method.     

Polymerization of propylene by zirconocenium catalysts with different counter-ions

Propylene was polymerized by binary zirconocenium catalysts derived from rac-ethylenebis(1-η⁵-indenyl)dimethylzirconium and cation forming agents (C₆H₅)₃C+(C₆F₅)₄B^? and (C₆F₅)₃B. Polymerizations were also performed with the ternary systems of Et[Ind]₂ZrCl₂, Et₃Al, and the cation forming agents. The catalyst systems, with the inert noncoordinating counter-ion, (C₆F₅)₄B^?, have much higher activity and stereoselectivity than the ones with the CH₃B^?(C₆F₅)₃ counter-ion. Much less active still are catalysts having BF₄^? or (C₆H₅)₄B^? counter-ions. Similar but smaller effects of counter-ion structure on ethylene polymerization were observed. © 1994 John Wiley & Sons, Inc.     

Polymerization of methyl methacrylate with cobalt acetylacetonate-diethyl zinc catalyst system

Polymerization of methyl methacrylate was studied with a cobalt acetylacetonate-diethyl zinc catalyst initiator system in benzene medium at 40°C. When the stoichiometric ratio of Zn/Co is 2, the activity for polymerization is found to be maximum. The structure of the obtained polymethyl methacrylate is compared with that obtained using a free-radical initiator such as benzoyl peroxide. The structure of polymer and the M?_w/M?_n values indicate that cobalt acetylacetonate-zinc diethyl system has pronounced free-radical characteristics. A suitable mechanism is proposed from the kinetic studies. © 1995 John Wiley & Sons, Inc.     

Polymerization of phenylacetylene by iridium catalysts

Polymerization of phenylacetylene (PA) with [(cod)IrCl]₂‐based catalysts (cod: 1,5‐cyclooctadiene) was examined. The [(cod)IrCl]₂/n‐BuLi and [(cod)IrCl]₂/Ph₂C?C(Ph)Li systems induced the polymerization of PA to produce polymers with a number‐average molecular weight (M_n) of around several thousand in rather low yields. On the other hand, the catalyst composed of [(cod)IrCl]₂, norbornadiene (nbd), Ph₃P, and Ph₂C?C(Ph)Li (molar ratio of 1:1:1.1:2) produced polymer in a high yield (ca. 80%) in toluene at 0 °C. The resulting polymer showed a bimodal gel permeation chromatographic profile (M_n = 209,000 and 4300; ratio: 81/19). On the basis of these findings, the presence of two active species, that is, Ir complexes with nbd and cod, are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1075–1080, 2002     

Polymerization of propene by post-metallocene catalysts

In the last few years several non-metallocene catalysts have been disclosed as efficient catalysts for the stereospecific polymerization of propene. In this paper we summarize some recent literature data and some new results concerning the stereochemical mechanism of propene polymerization promoted by late transition metal systems and group 4 metal bis(phenoxyimine) systems. NMR analysis of the fine structure of the polymers obtained, in some cases using isotopically enriched reagents, provides valuable information on the regiochemistry and stereochemistry of the polymerization.     

Reaction between isoprene and aniline on complex palladium catalysts

Isoprene and aniline have been reacted on the catalytic system Pd(acac)₂-Ph₃P to form a mixture of isomeric telomers: N-(dimethyloctadien-2,7-yl-1)anilines and N-(dimethyloctadien-1,7-yl-3)anilines but on the catalytic system Pd(acac)₂-Ph₃P-CF₃COOH the main product is a mixture of N-(methylbuten-2-yl)aniline adducts. The reaction between N-methylaniline and isoprene on the latter catalyst also gives a mixture of N-methyl and N-(methylbuten-2-yl)aniline adducts.A. N. Nesmeyanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1794–1798, August, 1992.     

Polymerization of alkoxyallenes by transition-metal catalysts

The structure of polymers obtained by polymerization of methoxyallene and ethoxyallene with transition-metal catalysts depends on the catalyst employed. Rapid polymerization at 0°C through the unsubstituted double bond occurred with π-allylnickel halides, NiCl₂/AlEt₃ and CoCl₂/AlEt₃, yielding polymers with the structure Typical Ziegler–Natta catalysts (TiCl₄, VOCl₃ or FeCl₃ with AIEt₃) gave polymers mainly with the structure although some of the structural units were probably present as well. Polymers having conjugated double bonds were prepared with PdCl₂, [(π-allyl)PdCl]₂, and PdCl₂(C₆H₅CN)₂ as catalysts. Palladium iodide produced polymers with all three of the above structural units present. Polymerization occurred more slowly with these palladium catalysts. A preliminary examination of the effect of variation of solvent, ligand, co-catalyst, and temperature on the rate and structure of the polymers obtained with the palladium catalysts is reported.