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Alcohol‐Induced C−N Bond Cleavage of Cyclometalated N‐Heterocyclic Carbene Ligands with a Methylene‐Linked Pendant Imidazolium Ring
Author(s) -
Zhong Wei,
Fei Zhaofu,
Scopelliti Rosario,
Dyson Paul J.
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201602267
Subject(s) - carbene , chemistry , methylene , bond cleavage , medicinal chemistry , iodide , dimer , ether , imidazole , stereochemistry , photochemistry , organic chemistry , catalysis
Reaction of the pentamethylcyclopentadienyl rhodium iodide dimer [Cp*RhI 2 ] 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 S N 2 mechanism for the reaction is tentatively proposed.