Wolfgang Schattenmann

A Novel Class of Ruthenium Catalysts for Olefin Metathesis

The different nature of carbene ligands is clearly demonstrated by the first ruthenium-based complexes 1, which contain both alkylidene and N-heterocyclic carbene moieties. The latter exhibit a pronounced Lewis base behavior. Moreover, this difference forms the basis of the high catalytic activities of these compounds in olefin metathesis reactions.

EINE NEUE GENERATION VON RUTHENIUMKATALYSATOREN FUR DIE OLEFINMETATHESE

Die unterschiedliche Natur von Carbenliganden ist eindrucksvoll bewiesen durch die ersten auf Ruthenium basierenden Komplexe 1, die sowohl uber Alkyliden- als auch uber N-Heterocyclen-Carbeneinheiten verfugen. Letztere haben ein ausgepragtes Saure-Base-Verhalten. Daruber hinaus ist es gerade dieser Unterschied, der die Grundlage fur die hohen Katalyseaktivitaten dieser Verbindungen bei der Olefinmetathese bildet.

N-Heterocyclic carbenes: application of ruthenium–alkylidene complexes in ring-opening metathesis polymerization

Abstract Novel ruthenium–alkylidene catalysts bearing N-heterocyclic carbenes were applied in ring-opening metathesic polymerization (ROMP) reactions of various norbornene derivatives. High tolerance towards polar functional groups as well as high catalytic activity is demonstrated. The combination of N-heterocyclic carbenes and coordinatively labile ligands (phosphanes or chloro-bridged transition metals) on the ruthenium center proves not only successful regarding catalytic performance but also promising with respect to polymer properties.

Synthesis of polymers with a controlled molecular weight via ring-opening metathesis polymerization (ROMP) with a ruthenium-based catalyst

Various bisallylic ruthenium(IV) complexes in combination with certain diazoalkanes show high catalytic activities in the ring-opening metathesis polymerization (ROMP) of norbornene and its derivatives. In particular, dicationic complexes in the presence of ethyl diazoacetate were found to be extraordinarily efficient. The ionic character of the catalyst determines the use of polar solvents and therefore the precipitation polymerization of monomers like norbornene. The ratio of methanol to dichloromethane in the solvent mixture could be used to adjust the number-average molecular weight of polynorbornene in the range of 3 x 105 g/mol up to 1 x 106 g/mol at a constant monomer to catalyst ratio of 1 x 103/1. By polymerizing norbornene in neat methanol, the number-average molecular weights could be varied between 2 x 103 and 3 x 105 g/mol by the addition of certain quantities of 1-octene as a chain-transfer agent. According to the proposed mechanism, these polymers contain equivalent amounts of heptylidene a...