Catalytic living ring-opening metathesis polymerization

In living ring-opening metathesis polymerization (ROMP), a transition-metal–carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well- defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst

Selective propene oligomerization with nickel(II)-based metal-organic frameworks

Two Ni2+-containing metal-organic frameworks, Ni 2(dobdc) and Ni2(dobpdc), are shown to be active for the oligomerization of propene in the gas phase. The metal-organic frameworks exhibit activity comparable to Ni2+-exchanged aluminosilicates but maintain high selectivity for linear oligomers. Thus, these frameworks should enable the high yielding synthesis of linear propene oligomers for use in detergent and diesel fuel applications. © 2014 American Chemical Society

Selective propene oligomerization with nickel(II)-based metal-organic frameworks

Two Ni2+-containing metal-organic frameworks, Ni 2(dobdc) and Ni2(dobpdc), are shown to be active for the oligomerization of propene in the gas phase. The metal-organic frameworks exhibit activity comparable to Ni2+-exchanged aluminosilicates but maintain high selectivity for linear oligomers. Thus, these frameworks should enable the high yielding synthesis of linear propene oligomers for use in detergent and diesel fuel applications. © 2014 American Chemical Society

Cyclometalated Ruthenium Alkylidene Complexes: A Powerful Family of Z -Selective Olefin Metathesis Catalysts

The past 5 years have witnessed an enormous growth in the field of Z-selective olefin metathesis. The development of a new class of cyclometalated ruthenium-based catalysts has extended the utility of olefin metathesis to the synthesis of useful Z-olefin-containing small molecules, polymers, and natural products. This review highlights the recent advances in the area of Z-selective olefin metathesis employing cyclometalated ruthenium alkylidene catalysts, with particular focus on its applications and mechanistic basis. A deeper understanding of structure–activity relationships should aid in the future design of even more active and selective olefin metathesis catalysts