“…3 Relatively simple synthetic procedures leading to precursor imidazolium salts have been elucidated, 4 and many routes that allow the introduction of an NHC ligand to a metal centre have been developed. The reaction of imidazolium salts with silver oxide giving an NHC complex of silver, which serves as a useful trans-metallating reagent, has proved particularly popular, [5][6][7][8] and we use it in this paper. Other interesting methods include the utilisation of an electron-reservoir complex, together with air, to generate NHCs, 9 or the use of imidazolium-2-carboxylates which lose CO 2 to generate NHCs, 10 though, increasingly, direct reaction of the imidazolium salt with the metal has found favour.…”