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

Abstract

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‐κ3‐NPN’ tridentate coordination to the metal center, one with an interionic POH⋅⋅⋅FPF5 hydrogen bond in the crystal. A paramagnetic nickel [Ni3(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 κ2‐NO, two are monodentate κ‐O and is connected to the other two nickel centers by two sets of bridging μ2‐O,P moieties. Non‐central nickel centers are each coordinated to one bidentate ligand κ2‐PN and one monodentate ligand κ‐P.

Synthesis of Pd-NNP Phosphoryl Mononuclear and Phosphinous Acid-Phosphoryl-Bridged Dinuclear Complexes and Ambient Light-Promoted Oxygenation of Benzyl Ligands

“…Lithiation of 6-methyl-2,2′-bipyridine ( 1a ) was performed using 3.0 equiv of lithium N , N -diisopropylamide (LDA), and the subsequent reaction with 1.0 equiv of ethyl phenylphosphinate that was used for the synthesis of alkyl­(phenyl)­phosphine oxides afforded NNP­(O)H preligand 2a in 60% isolated yield as a yellow oil (Scheme ). The lithiation of 2-Me groups in 2-methylpyridine and 2-methylquinoline by LDA has been used to prepare NP­(O)­HN preligands . Similar to 2a , MeNNP­(O)H preligand 2b was obtained from 6,6′-dimethyl-2,2′-bipyridine ( 1b ) in 35% isolated yield as a yellow oil, which solidified upon exposure to air at room temperature to afford a white solid.…”

“…To utilize the cooperative effects of the PA ligand (or phosphoryl ligand) and the transition metal in catalysis, such as oxygenation shown in Scheme , SPO preligands that do not form strong intramolecular hydrogen bonding are required. Tridentate preligands − including an SPO moiety are promising, and PP­(O)­HP and NP­(O)­HN preligands and their late transition metal complexes have been reported. ,− We designed novel tridentate NNP­(O)H preligands, including a 2,2′-bipyridine (bpy) and an SPO moiety, which can be readily prepared from bpys and a phosphinic acid ester, and Pd complexes formed from the preligands (Figure ). Here, we reported the synthesis of NNP­(O)H preligands, the complexation of the preligands with Pd, and the reaction of the synthesized dinuclear PdBn complex with O 2 promoted by ambient light.…”