Ruthenium complexes of chelating amido-functionalized N-heterocyclic carbene ligands: Synthesis, structure and DFT studies

Abstract

Synthesis, structure and density functional theory (DFT) studies of a series of new ruthenium complexes, [1-(R)-3-N-(benzylacetamido)imidazol-2-ylidene]RuCl(p-cymene) [R = Me (1c), i-Pr (2c), CH2Ph (3c); p-cymene = 4-i-propyltoluene] supported over N/O-functionalized N-heterocyclic carbene (NHC) ligands are reported. In particular, the ruthenium (1–3)c complexes were synthesized from the respective silver complexes, [1-(R)-3-N-(benzylacetamido)imidazol-2-ylidene]2Ag + Cl − [R = Me (1b), i-Pr (2b), CH2Ph (3b)] by the treatment with [Ru(p-cymene)Cl2]2 in 65–76% yields. The molecular structures of (1–3)c revealed the chelation of the N-heterocylic carbene ligand through the carbene center and an amido sidearm of the ligand in all of the three complexes. The density functional theory studies on the ruthenium (1–3)c complexes indicated strong binding of the NHC ligand to the metal center as was observed from the deeply buried NHC-Ru σ-bonding molecular orbitals.