Reactivity of a Quinoline-Tethered N‑Heterocyclic Carbene with Polynuclear Ruthenium Carbonyls

The quinoline-functionalized N-heterocyclic carbene 1-(8-quinolyl)­methyl-3-methylimidazol-2-ylidene (QuinCH2ImMe) reacted with [Ru3(CO)12] at room temperature to give the monosubstituted derivative [Ru3(κCNHC-QuinCH2ImMe)­(CO)11] (1), which, upon heating in refluxing THF, underwent a thermally induced double C­(sp3)–H bond activation to give the dihydrido derivative [Ru3(μ-H)2(μ3-κ3N,C,CNHC-QuinCImMe)­(CO)8] (2). The mechanism of this transformation has been studied by DFT calculations. The room-temperature reaction of QuinCH2ImMe with [Ru4(μ-H)4(CO)12] initially gave the imidazolium salt [QuinCH2ImHMe]­[Ru4(μ-H)3(CO)12], but it evolved to the monosubstituted tetranuclear derivative [Ru4(μ-H)4(κCNHC-QuinCH2ImMe)­(CO)11] (3) when it was heated in refluxing toluene.