Synthesis of high polymers from substituted acetylenes: exploitation of molybdenum- and tungsten-based catalysts

This review deals with recent advances in the synthesis, characterization, and function of poly-acetylenes with substituents (substituted polyacetylenes). The main features are as follows: A number of catalysts based on group 5 and 6 transition metals (Nb, Ta, Mo, W) have been exploited which polymerize substituted acetylenes, especially sterically crowded ones. By using these catalysts, new substituted polyacetylenes [—(—CR=CR′—)n—] with molecular weight up to one million have been synthesizedfrom various monomers; e.g., HC≡C—t—Bu, MeC≡C—n—C5H11, MeC≡CPh, ClC≡CPh, and McC≡CSiMe3. Unlike polyacetylene, these substituted polyacetylenes are generally colorless (or light yellow), soluble, amorphous, air-stable, electrically insulating, and non-paramagnetic. Some of these polymers have been found to be useful as membranes for separation of gases and liquids, thus constituting a new category of speciality polymers.

Polyacetylenes with substituents: Their synthesis and properties

For many years, considerable research efforts have been dedicated to π-conjugated polymers because of their extraordinary electronic, optical, and structural properties. The employed transition-metal-based initiating systems comprise not only simple transition-metal salts but also rather sophisticated mixtures of two, three, or four compounds and even highly defined single-component systems such as transition-metal alkylidene complexes. Extensive fine-tuning of the electronic and steric properties of initiator–monomer systems eventually allowed the tailor-made synthesis of conjugated materials via living polymerization techniques. This article focuses on recent developments in the field of the living polymerization of substituted acetylene derivatives. Ill-defined group 5 and 6 transition metal halide-based initiators, well-defined transition-metal alkylidene complexes, and rhodium(I)-based systems that induce the living polymerization of numerous substituted acetylenes are reviewed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5723–5747, 2005

Living polymerization of substituted acetylenes

Light activation is a most desirable property for catalysis control. Among the many catalytic processes that may be activated by light, olefin metathesis stands out as both academically motivating and practically useful. Starting from early tungsten heterogeneous photoinitiated metathesis, up to modern ruthenium methods based on complex photoisomerisation or indirect photoactivation, this survey of the relevant literature summarises past and present developments in the use of light to expedite olefin ring-closing, ring-opening polymerisation and cross-metathesis reactions.

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-6-127.pdf

Light-induced olefin metathesis

Olefin Metathesis with 1,1-Difluoroethylene

Reaction de metathese des olefines induite photochimiquement en presence d'un complexe de metal de transition : VI. Existence probable d'un metallodichlorocarbene primaire

P. Krausz

Papers

Reaction de metathese des olefines induite photochimiquement en presence d'un complexe de metal de transition : VI. Existence probable d'un metallodichlorocarbene primaire