Abstract
New phenoxybenzylidene ruthenium chelates were synthesised from the second generation Grubbs catalysts bearing a triphenylphosphine ligand (or its para-substituted analogues) by metathesis exchange with substituted 2-vinylphenols. The complexes behave like a latent catalyst and are characterized by an improved catalytic behaviour as compared to that of the known analogues, i.e., they exhibit high catalytic inactivity in their dormant forms and a profound increase in activity after activation with HCl. The strong electronic influence of substituents in the chelating ligand on the catalytic activity was demonstrated. The catalytic properties were tested in ROMP of cyclooctadien (COD) and a single selected norbornene derivative.
Highlights
Olefin metathesis is nowadays one of the most important methods for the formation of carbon–carbon bonds in organic and polymer chemistry [1,2]
Searching for improved latent catalysts that are less reactive in dormant form and highly active in the presence of an chemical activator, we report the synthesis and catalytic performance of new phenoxybenzylidene ruthenium chelates modified by introduction of electron donating and electron withdrawing substituents at the benzylidene ligand in para position to the coordinating oxygen and bearing instead of a strong sigma-donor ligand – tricyclohexylphosphine a weaker sigma-donor – a triphenylphosphine ligand or its derivatives
Complexes containing triphenylphosphine ligands and substituted triphenylphosphine ligands were isolated in high yields (95–98%) according to the methodology described by Grubbs (Scheme 1) [11]
Summary
Olefin metathesis is nowadays one of the most important methods for the formation of carbon–carbon bonds in organic and polymer chemistry [1,2]. In the presence of 2 equivalents of HCl (used in the form of 2.0 M solution in diethyl ether) as an activating agent, complex 1a was capable for providing a complete conversion after a few minutes of the reaction.
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