One of the most exciting developments in the areas of catalysis, organometallic chemistry, and polymer science in recent years has been the intense exploration and commercialization of new polymerization technologies based on single-site and metallocene coordination olefin polymerization catalysts.1 The vast number of specifically designed/synthesized transition metal complexes (catalyst precursors) and main-group organometallic compounds (cocatalysts) allows unprecedented control over polymer microstructure, the generation of new polymer architectures, and the development of new polymerization reactions. Commercialization of new generations of single-site and metallocene catalyst-based technologies has provided the multibillion pound per year polyolefins industry with the ability to deliver a wide range of new and innovative olefin-based polymers having improved properties.2-4 The intense industrial activity in the field and the challenges to our basic understanding that have come to light have in turn 1391 Chem. Rev. 2000, 100, 1391−1434

/pdf/cocatalysts-for-metal-catalyzed-olefin-polymerization-37a9jvjiei.pdf

Cocatalysts for Metal-Catalyzed Olefin Polymerization: Activators, Activation Processes, and Structure−Activity Relationships

The advent of well-defined catalysts for olefin metathesis which combine high activity, durability, and excellent tolerance towards polar functional groups has revolutionized the field. The past decade has seen the rapid embrace of these reagents as tools for advanced organic and polymer chemistry and the success of this development is witnessed by a plethora of elegant applications to the synthesis of natural and nonnatural products. This review article provides an overview of these developments and intends to familiarize the reader with some very recent advances which hold the promise to expand the scope of the reaction even further. Moreover, the positive impact of metathesis on the fundamental logic of retrosynthetic planning is demonstrated by means of typical examples. Finally, it will be shown that metathesis is by no means restricted to alkenes as substrates, and some comments on metathesis reactions following unconventional mechanistic pathways will also be presented.

Olefin Metathesis and Beyond

Selectivity in propene polymerization with metallocene catalysts.

2.2.1. Polyisocyanates 6117 2.2.2. Polysilanes 6118 2.2.3. Polyacetylenes 6120 2.3. Foldamer-Based Helical Polymers 6124 2.3.1. Click Polymerization 6126 2.3.2. Ring-Closing Reaction 6126 2.4. Other Types of Helical Polymers 6127 2.4.1. π-Conjugated Helical Polymers 6127 2.4.2. Metallosupramolecular Helical Polymers 6128 2.5. Induced Helical Polymers 6130 2.5.1. Induced Helical Polyacetylenes 6130 2.5.2. Other Induced Helical Polymers and Oligomers 6132

Helical polymers: synthesis, structures, and functions

Living ring-opening metathesis polymerization

Publisher Summary This chapter discusses crystalline high polymers of α-olefins. The linear crystalline polymers of α-olefins are synthesized and the chapter also discusses the properties of crystalline polypropylene, poly-α-butylene, and polystyrene. Depending on the structure of the catalyst, different amounts, ranging from 0 to 100%, of the polymerization products are crystallizable and can be separated easily from the much more soluble noncrystalline polymers by solvent extraction. The new crystalline poly hydrocarbons have higher melting point, higher density, and lower solubility in organic solvents than the corresponding amorphous polyhydrocarbons having intrinsic viscosity of the same order of magnitude. The infrared spectra of crystalline polypropylene, of melted samples of the same polymer and of the amorphous polypropylene, show between 2 and 7.5 μ, the high adsorption regions characteristic of hydrocarbons.

CRYSTALLINE HIGH POLYMERS OF α-OLEFINS

Die Polymerisation von Cycloolefinen ist — ahnlich wie die von Olefinen mit innenstandiger Doppelbindung — sterisch behindert. Mit anionisch-koordinativ wirkenden Ziegler-Katalysatoren ist es in den letzten Jahren gelungen, Copolymere mit Athylen zu gewinnen. Es kommt dabei stets zu einer cis-Offnung der olefinischen Doppelbindung. Trotz der sterischen Hinderung konnten auch Cyclobuten und Cyclopropen homopolymerisiert werden, unter Aufrichten der Doppelbindung. — Fur die Homopolymerisation des Cyclopentens sind uberraschenderweise bei der Athylen-Polymerisation wenig wirksame Katalysatoren die besten: Unter Ringspaltung erhalt man mit MoCl5/Al(C2H5)3 cis-Polypentenamer, mit WCl6/Al(C2H5)3 trans-Polypentenamer. Beide Polypentenamere haben kautschukartige Eigenschaften. — Nach IR-Spektren und oxydativem Abbau sind im trans-Polypentenamer die Monomereinheiten Kopf-Schwanz-verknupft. Vermutlich wird die zur Doppelbindung benachbarte Einfachbindung geoffnet. — Bei −50°C konnte am kristallinen, um 400% gestreckten trans-Polypentenamer rontgenographisch die Kristallstruktur bestimmt werden.

Stereospezifische Homopolymerisation des Cyclopentens

Publisher Summary This chapter discusses the nature of some soluble catalysts for low-pressure ethylene polymerization. Soluble catalysts for the low-pressure ethylene polymerization have been found which are less active than the best heterogeneous catalysts, but which are much more suitable for the basic research on chemical nature of the catalysts. The soluble catalytic system obtained from organo-aluminium compounds and Ti compounds in which the Ti atom is bound to two cyclopentadienyl groups. A crystallizable bimetallic complex has been synthesized which is a catalyst for the polymerization of ethylene. It can be concluded that the Ziegler-type polymerization catalysts are complexes containing organometallic bonds and more than one metal atom.

The nature of some soluble catalysts for low pressure ethylene polymerization

The copolymerization of ethylene with cyclopentene and with cyclohexene in the presence of catalytic systems acting through an anionic co-ordinated polymerization mechanism is described. In the case of cyclopentene it was possible to obtain crystalline alternating copolymers with stereoregular structure using either catalytic systems acting in the heterogeneous phase or those acting in the homogeneous phase. The structure of the polymeric chains and the properties of these new polymers are described. The fact that the ethylene-cyclopentene copolymers are much more rich in cycloolefin units than the corresponding ethylene-cyclohexene copolymers is attributed to phenomena of steric hindrance.



Die Copolymerisation von athylen mit Cyclopenten oder Cyclohexen in Gegenwart von Katalysatorsystemen mit anionisch-koordiniertem Polymerisationsmechanismus wird beschrieben. Im Fall des Cyclopentens ist es moglich gewesen, kristalline alternierende Copolymere mit sterisch geordneter Struktur zu erhalten, und zwar sowohl mittels Katalysatorsystemen, die in heterogener, als auch mittels solcher, die in homogener Phase wirken. Die Struktur der Polymerketten und die Eigenschaften dieser kristallinen Polymeren werden beschrieben. Die Tatsache, das die athylen-Cyclopenten-Copolymeren sehr viel reicher an Cycloolefin-Einheiten sind als diejenigen des athylens mit Cyclohexen, wird auf Phanomene sterischer Hinderung zuruckgefuhrt.

Giorgio Mazzanti

Papers

CRYSTALLINE HIGH POLYMERS OF α-OLEFINS

Stereospezifische Homopolymerisation des Cyclopentens

The nature of some soluble catalysts for low pressure ethylene polymerization

Crystalline alternating ethylene-cyclopentene copolymers and other ethylene-cycloolefin copolymers

Ethylene–propylene copolymerization in the presence of catalysts prepared from vanadium triacetylacetonate