Olefin Metathesis Catalysts Containing Acyclic Diaminocarbenes

Abstract

The first examples of ruthenium-based olefin metathesis catalysts containing acyclic diaminocarbene (ADC) ligands are reported. Complexes of the type (ADC)(SIMes)Cl 2 RudCHPh andwere 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.

Ru-based Z-selective metathesis catalysts with modified cyclometalated carbene ligands

“…Previously, non-cyclometalated metathesis catalysts with acyclic diaminocarbenes have provided metathesis products with lower E :Z ratios than analogous catalysts containing NHC ligands. 24 Based on these observations, it was anticipated that C–H activation of these acyclic diaminocarbene ruthenium complexes might lead to improved Z -selective metathesis catalysts. However, acyclic formamidinium salts 23 and 24 underwent metalation to produce an unstable dichloride that could not be isolated without substantial decomposition.…”

Tuning the luminescence of transition metal complexes with acyclic diaminocarbene ligands

“…Due to the acyclic structure, rotation around the C carbene -N bonds is enabled allowing for the acyclic diaminocarbene ligand to adopt various conformations with differing steric and electronic characteristics. [50][51][52] For instance, in carbene species having small substituents, a rotation barrier of the C carbene -N bonds is lower than 13 kcal/mol as indicated by experimental 53 and theoretical 54 studies. Rotational flexibility plays a significant role in the photoemissive properties: 55 Ref.…”

Untitled

“…Sulfur, methyl iodide and triethyl orthoformate were purchased from SD Fine-Chem Limited and used as received. Compound N,N'-Bis (2,6-di-isopropylphenyl)-N,N'dimethylformamidinium Iodide (1) was prepared by literature procedures [20][21].…”