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Although ring-opening olefin metathesis polymerization (ROMP) has been recognized as a method of polymerization since the 1960s, it was only with the development of well-defined metathesis catalysts that the reaction could be controlled. The demonstration that ROMP was ‘living’ with the many of the alkylidene-metal complexes allowed the preparation of new families of polymers with precise molecular weights, polydispersities, and topologies. The application of organometallic techniques to the design of new initiators has resulted in efficient and reliable synthetic processes and the development of a variety of new applications for the resulting polymeric structures.

Olefin cross-metathesis has become an indispensable tool for efficient carbon–carbon bond formation. Fundamental studies on functional group tolerance and an understanding of the steric and electronic factors crucial to product selectivity have led to the development of an empirical model for reaction design. Due to the copious amount of recent literature pertaining to this reaction, this review focuses on reports pertaining to important aspects in either the concept or the application of alkene cross-metathesis. Strategies for effecting highly selective cross-metathesis reactions will be presented and discussed.

The alkene metathesis reaction between carbon–carbon double bonds is now a well-established synthetic method in industrial operations and in the laboratory1 Recently it has been recognized that a closely related, transition metal catalyzed reaction takes place between a carbon–carbon double bond and a carbon–oxygen double bond.2 This latter process, which can be considered as a Wittig analog, shows promise of becoming an important tool of synthesis strategy.3

Titanacyclobutanes, catalysts for living ring opening metathesis polymerization (ROMP) of strained cyclic olefins, have been transformed into Ziegler-Natta catalysts. The synthetic routes that allow the transformation of 3,3-dimethylcyclopropene-titanacyclobutane 1, the most effective initiator of these ROMP polymerizations, and of trisubstituted titanacycles, such as 3, into the corresponding chlorine or ethoxy derivatives are reported. When trimethylaluminum is added to 1, 8 and 9 new alkylidene methyl-bridged bimetallic complexes, that can be considered as borderlines between metathesis and Ziegler-Natta catalysts, are obtained.

Organometallic polymers have been used as catalysts for a large number of reactions. These catalysts are prepared by attaching a homogeneous catalyst to a polymeric support by a linking ligand. In order to understand some of the aspects of these catalysts, two analytical techniques have been explored. Election microprobe spectroscopy has been used to measure the radial distribution of the catalyst and linking agent inside of a support. Phosphorus nuclear magnetic resonance spectroscopy has been found to be an efficient, rapid means of analysis of low cross-linked phosphinated polymers. The results give a structure for the catalyst on the polymer.

Monomers containing two ligand groups separated by either flat aromatic groups or long alkyl chains were prepared. These materials were use to make polymers in with nickel(II) or phi-rhodium(I) halides were used to link the monomer units. The major part of the study used 1,12-bis(diphenylphosphino)-dodecane as the monomer unit. Polymethylmethacrylate-Pt composites were evaluated as oxidation catalysts and as electrode coatings. (Author)