Wei Zhong1,2, Zhaofu Fei1, Rosario Scopelliti1, Paul J Dyson3. 1. Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland. 2. College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, 314001, China. 3. Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland. paul.dyson@epfl.ch.
Abstract
Reaction of the pentamethylcyclopentadienyl rhodium iodide dimer [Cp*RhI2 ]2 with 1,1'-diphenyl-3,3'-methylenediimidazolium diiodide in non-alcohol solvents, in the presence of base, led to the formation of bis-carbene complex [Cp*Rh(bis-NHC)I]I (bis-NHC=1,1'-diphenyl-4,4'-methylenediimidazoline-5,5'-diylidene). In contrast, when employing alcohols as the solvent in the same reaction, cleavage of a methylene C-N bond is observed, affording ether-functionalized (cyclometalated) carbene ligands coordinated to the metal center and the concomitant formation of complexes with a coordinated imidazole ligand. Studies employing other 1,1'-diimidazolium salts indicate that the cyclometalation step is a prerequisite for the activation/scission of the C-N bond and, based on additional experimental data, a SN 2 mechanism for the reaction is tentatively proposed.
Reaction of the pentamethylcyclopentadienyl rhodium iodide dimer [Cp*RhI2 ]2 with 1,1'-diphenyl-3,3'-methylenediimidazolium diiodide innon-n class="Chemical">alcohol solvents, in the presence of base, led to the formation of bis-carbene complex [Cp*Rh(bis-NHC)I]I (bis-NHC=1,1'-diphenyl-4,4'-methylenediimidazoline-5,5'-diylidene). In contrast, when employing alcohols as the solvent in the same reaction, cleavage of a methylene C-N bond is observed, affording ether-functionalized (cyclometalated) carbene ligands coordinated to the metal center and the concomitant formation of complexes with a coordinated imidazole ligand. Studies employing other 1,1'-diimidazolium salts indicate that the cyclometalation step is a prerequisite for the activation/scission of the C-N bond and, based on additional experimental data, a SN 2 mechanism for the reaction is tentatively proposed.
Authors: Mateusz K Cybulski; Nicholas A Beattie; Stuart A Macgregor; Mary F Mahon; Michael K Whittlesey Journal: Chemistry Date: 2020-07-28 Impact factor: 5.236