Syntheses, characterization and redox properties of oxo-centred triruthenium cluster dimers and trimers linked by ortho-metallated polypyridyl ligands

A series of mono-, di- and trimeric oxo-centred triruthenium cluster compounds with ortho-metallated polypyridyl ligands were prepared by reaction of oxo-centred triruthenium precursor compound Ru3O(OAc)6(py)2(CH3OH)]+ (1) with bis(2,2'-bipyridin-5-yl)butadiyne (bpyCtriple bond, length as m-dash]C-Ctriple bond, length as m-dash]Cbpy), bis(2,2'-bipridin-5-yl)ethyne (bpyCtriple bond, length as m-dash]Cbpy), 2,2'-bipyrazine (bpz), pyrazino2,3-f]quinoxaline (pyq), or 4,7-phenanthroline (4,7-phen). As revealed by redox wave splitting, electronic interactions are operating between two Ru3O redox centres in most of the triruthenium cluster dimers and trimers. The cluster-cluster interactions are highly sensitive to the variations in bonding modes of the polypyridyl ligands. Ortho-metallation of the bridging ligand induces an enhanced electronic interaction between two triruthenium centres.