Tridentate NPN Ligands with a Central Secondary Phosphine Oxide Donor and their Corresponding Metal Complexes

Three new Ru complexes with N-P(OH)-N donor ligands were synthesized and characterized. A ruthenium complex with a ligand with quinolinyl side arms exhibited monodentate coordination through the phosphorus atom with an intramolecular POH...N(quinolinyl) hydrogen bond but with no interaction between nitrogen donors and the ruthenium center. Two pentamethylcyclopentadienyl ruthenium complexes with a ligand with pyridyl side arms exhibited fac-kappa(3)-NPN' tridentate coordination to the metal center, one with an interionic POH...FPF5 hydrogen bond in the crystal. A paramagnetic nickel [Ni-3(N-P(O)-N)(4)] cluster was also characterized; the crystal structure shows three nickel centers in two different environments. The central nickel is coordinated to four deprotonated ligands, two are bidentate kappa(2)-NO, two are monodentate kappa-O and is connected to the other two nickel centers by two sets of bridging mu(2)-O,P moieties. Non-central nickel centers are each coordinated to one bidentate ligand kappa(2)-PN and one monodentate ligand kappa-P.