A series of ruthenium(II) carbonyl chloride complexes with pyridine-functionalised N-heterocyclic carbenes, trans(Cl)- and cis(Cl)-[Ru(Py–NHC)(CO)2Cl2] [Py–NHC = 3-tert-butyl-1-(2-pyridyl)imidazol-2-ylidene, 1a and 1b; 3-n-butyl-1-(2-pyridyl)imidazol-2-ylidene, 2a and 2b; 3-tert-butyl-1-picolylimidazol-2-ylidene, 3a and 3b; 3-n-butyl-1-picolylimidazol-2-ylidene, 4a and 4b; 3-benzyl-1-picolylimidazol-2-ylidene, 5a and 5b] have been prepared by transmetallation from the corresponding silver carbene complexes and characterised by elemental analyses, infrared and 1H and 13C NMR spectroscopies. The yields of trans(Cl)- and cis(Cl)-isomers could be controlled by altering the reaction conditions: the trans-isomers were kinetically formed as the main products in 60–70% yield in CH2Cl2 at ambient temperature while the thermodynamic cis-isomers were obtained as the major products in 70–80% yield in toluene at refluxing temperature. The trans-isomer was transformed into the thermodynamic cis-isomer by heating in CH2Cl2 in a Teflon-lined stainless autoclave for 24 h at 120 °C. The molecular structures of 1a, 1b, 2b, and 4b have been determined by single-crystal X-ray diffraction. These complexes showed catalytic activities in hydrogen transfer reactions of ketones.
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?