Reactivity of Phosphine- and Thioether-Tethered N-Heterocyclic Carbenes with Ruthenium Carbonyl

Abstract

The reactions of the NHC-functionalized phosphines 1-[{2-(diphenylphosphino)phenyl}methyl]-3-methylimidazol-2-ylidene (Ph2PC6H4CH2ImMe) and 1-[{2-(dicyclohexylphosphino)phenyl}methyl]-3-methylimidazol-2-ylidene (Cy2PC6H4CH2ImMe) and the NHC-functionalized thioether 1-{(2-methylsulfide)ethyl}-3-methylimidazol-2-ylidene (MeSCH2CH2ImMe) with [Ru3(CO)12] have been studied. Both NHC-phosphines react with equimolar amounts of [Ru3(CO)12], in THF at room temperature, to give the edge-bridged disubstituted products [Ru3(μ-κ2P,CNHC-R2PC6H4CH2ImMe)(CO)10], R = Ph (1), Cy (2), which selectively undergo a double C–H bond activation of their CH2 group upon gentle warming (R = Ph) or at room temperature (R = Cy) to give the dihydrido derivatives [Ru3(μ-H)2(μ3-κ3P,C,CNHC-R2PC6H4CImMe)(CO)8], R = Ph (3) and Cy (4), respectively. These products contain novel face-capping ligands that arise from the oxidative addition of both C–H bonds of the corresponding NHC-phosphine ligand CH2 group. This double-metalation process is f...