Tris bridging ligand

Tri- and tetrametaphosphimates can act as polydentate ions. In principle, coordination by both nitrogen and oxygen is possible, but as seen in the salts of monovalent cations, almost exclusively coordination via oxygen is expected. Thus, the anions can act as polydentate and/or bridging ligands. The trimetaphosphimate ion can act in various ways ... 

The Ns-terdentate ligand bis(2-pyridylcarbonyl)amine, Hbpca = (54), is also a / -diketone, and ean therefore act as a bridging ligand. In the complexes [Fe(bpca)2][M (hfac)2]2, where = Fe, Mn, or Ni, the central iron, in its high ligand field Ng environment, is low-spin, while the iron eoordinated to hfac in the first complex is, as expected for its tris-/3-diketonate environment, high-spin." ... 

The synthesis and properties of [ Os(bpy)2 3(/r-181)] have been reported the formal oxidation state of the Os centers is +3. In contrast, [ Ru py)2 3(/i-181)] + contains Ru° with the bridging ligand possessing three semiquinone domains. The complex undergoes three reversible ligand-centered oxidations taking it ultimately to [ Ru(bpy)2 3(/i-181)]°" with (181) in a tris(quinone) form. The wavelength of the intense NIR absorption (MLCT) that the complex exhibits varies with oxidation state. " ... 

Ruthenium has a considerable propensity to form polynuclear complexes, particularly with carboxylate ligands which as bridging ligands span the Ru centres, sometimes accompanied by a bridging 0x0 ligand. Preparation and properties of bi- and tri-nuclear acetato complexes of Ru have been reviewed [552]. 

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