Olefin Metathesis Catalysts Containing Acyclic Diaminocarbenes

The first examples of ruthenium-based olefin metathesis catalysts containing acyclic diaminocarbene (ADC) ligands are reported. Complexes of the type (ADC)(SIMes)Cl2RuCHPh and (ADC)Cl2RuCH(2-isopropoxy)Ph (ADC = N,N′-dimesityl-N,N′-dimethylformamidin-2-ylidene or N,N′-bis(2,6-di-isopropylphenyl)-N,N′-dimethylformamidin-2-ylidene; SIMes = 1,3-dimesitylimidazolin-2-ylidene) were synthesized and studied in solution as well as in the solid state. Depending on their N-substituents and the metal center to which they were coordinated, the aforementioned ADC ligands were found to adopt different conformations. Preliminary investigations revealed that these Ru complexes exhibited high catalytic activities in a variety of olefin metathesis reactions at elevated temperatures and afforded cross-metathesis products with significantly lower E:Z ratios than catalysts containing analogous N-heterocyclic carbene ligands.