Synthesis and characterization of a tetraruthenium butterfly cluster containing a quadruply-bridging ligand derived from an N,N′-dipyrid-2-ylurea

The tetraruthenium cluster complex [Ru4(μ4-κ4-dmpu)(CO)10], H2dmpu = N,N′-bis(6-methylpyrid-2-yl)urea, has been prepared by treating [Ru3(CO)12] with H2dmpu in toluene at reflux temperature. An X-ray diffraction study has determined that this cluster has a butterfly metallic skeleton hold up by a doubly-deprotonated N,N′-bis(6-methylpyrid-2-yl)urea ligand (dmpu). This ligand has the pyridine N atoms attached to the wing-tip Ru atoms and the amido N atoms spanning Ru–Ru wing-edges, in such a way that the cluster has C2 symmetry. The donor atoms of doubly-deprotonated N,N′-dipyrid-2-ylureas seem to be appropriately arranged to hold butterfly tetranuclear clusters.