N-heterocyclic carbenes, part 33. Combining stable NHC and chelating pyridinyl-alcoholato ligands: A ruthenium catalyst for applications at elevated temperatures

Ruthenium alkylidene complexes bearing one NHC ligand and one chelating pyridinyl alcoholate ligand 6 are generated by exchange of a phosphine ligand. Two synthetic approaches are presented: reacting the NHC phosphine complex 5 with the chelating ligand or reacting the pyridinyl-alcohol-atophosphine complex 3 with a free NHC ligand. To evaluate the properties of 6 as metathesis catalysts, ROMP experiments with the strained olefin norbornene and the less strained cyclooctene were performed at different temperatures.