US scientists have come up with a general synthetic method to prepare macrocyclic tetracarbenes with first, second and third row transition metals from both sides of the periodic table, using a dimeric silver transmetallating reagent.
The facile synthesis of bidentate and tridentate N-heterocyclic carbenes (NHCs) coupled with their resistance to oxidation has made these chelating ligands an attractive alternative to phosphines for many applications. Despite numerous uses for these strong sigma-donor ligands, one class of chelating NHCs that has not been as thoroughly investigated is tetradentate carbenes.
Link to journal article
Exploiting a Dimeric Silver Transmetallating Reagent to Synthesize Macrocyclic Tetracarbene Complexes
Z Lu, S A Cramer and D M Jenkins
Chem. Sci., 2012, DOI: 10.1039/c2sc20628e