The reactivity of N-heterocyclic carbenes and their precursors with [Ru(3)(CO)(12)

The ambient temperature reaction of the N-heterocyclic carbenes (NHCs) 1,3-dimesitylimidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp) with the triruthenium cluster Ru(3)(CO)(12)], in a 3 : 1 stoichiometric ratio, results in homolytic cleavage of the cluster to quantitatively afford the complexes Ru(CO)(4)(NHC)] (; NHC = IMes, ; NHC = IDipp). Reaction of the 2-thione or hydrochloride precursors to IMes, i.e. Sdouble bond, length as m-dash]IMes and IMes.HCl, with the same triruthenium cluster affords the complexes Ru(4)(mu(4)-S)(2)(CO)(9)(IMes)(2)] () and Ru(4)(mu(4)-S)(CO)(10)(IMes)(2)] () (3 : 1 and 2 : 1 reaction), and {Ru(mu-Cl)(CO)(2)(IMes)}(2)] () (3 : 1 reaction) respectively. By contrast, the complex Ru(3)(mu(3)-S)(2)(CO)(7)(IMeMe)(2)] (), where IMeMe is 1,3,4,5-tetramethylimidazol-2-ylidene, is the sole product of the 2 : 1 stoichiometric reaction of Sdouble bond, length as m-dash]IMeMe with Ru(3)(CO)(12)]. Compounds -, and have been structurally characterised by single crystal X-ray diffraction.