Secondary phosphine oxide-triggered selective oxygenation of a benzyl ligand on palladium

Abstract

The oxygenation of a benzyl ligand on palladium was dramatically accelerated by using secondary phosphine oxides, selectively affording BnOOH or BnOH.

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

“…The two P−O distances are 1.534 (5) considerably shorter than that in the general hydrogen bonds and slightly longer than that in the intramolecular hydrogen bonds in 1 (2.418(4) and 2.407(4) Å), respectively. 14 The π−π interactions are observed between two bpy moieties and Bn and PhP moieties.…”

“…12,13 We have recently found that SPOs can accelerate the oxygenation of a benzyl ligand on Pd to afford BnOOH or BnOH selectively depending on the O 2 concentration (Scheme 2a). 14 The acceleration of the reaction toward O 2 is derived from the cooperative effect of the coordinated PA ligand and the Pd center (Scheme 2b). In this reaction, the oxygenation resulted in the formation of a stable dinuclear Pd complex, 1, including "quasi-chelate" structures by intramolecular hydrogen bonding between PA and phosphoryl ligands.…”

“…44,45 Structurally defined Au 11 clusters with monodentate phosphoryl ligands were also reported. 46 To utilize the cooperative effects of the PA ligand (or phosphoryl ligand) and the transition metal in catalysis, such as oxygenation shown in Scheme 2, 14 SPO preligands that do not form strong intramolecular hydrogen bonding are required. Tridentate preligands 47−49 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 have recently found that SPOs can accelerate the oxygenation of a benzyl ligand on Pd to afford BnOOH or BnOH selectively depending on the O 2 concentration (Scheme a) . The acceleration of the reaction toward O 2 is derived from the cooperative effect of the coordinated PA ligand and the Pd center (Scheme b).…”

“…The P−O distance (1.498(2) Å) is within the range of double bonds 37. In the case of 1, which has intramolecular hydrogen bonds, the P−O distances are in the range of 1.535(3)−1.552(3) Å, exhibiting intermediate values between the single and double bonds 14. Similarly, the reaction of 2b with [PdMe(Cl)(cod)] under O 2 afforded [PdCl-(MeNNP(O))] (3b) in high yield, which was soluble in organic solvents such as CHCl 3 in contrast to 3a.…”