1,1'-Binaphthyl-substituted diphosphene: synthesis, structures, and chiral optical properties

1,1'-Binaphthyl-substituted diphosphene 1 possessing a P[double bond, length as m-dash]P double bond and an axially chiral 1,1'-binaphthyl group was synthesized and fully characterized. Diphosphene 1 was prepared as an optically active form and thus is the first example of a chiral diphosphene. The CD spectra of 1 showed apparent circular dichroism in the longer wavelength region, caused by the P[double bond, length as m-dash]P moiety.

Palladium(II) complexes of bis(diphosphene) with different coordination behaviors

Organophosphorus compounds possessing a P-P double-bond character are intriguing materials in coordination chemistry because it is possible to form a variety of coordination modes from the π-bond in addition to the lone pairs. We report herein the complexation of a new bidentate ligand, ethylene-tethered bis(binaphthyldiphosphene) (S,S)-2, with palladium(II) species. The reaction of (S,S)-2 with [Pd(π-allyl)(cod)](SbF₆) and PdCl₂(cod) afforded η¹/η¹-bis(diphosphene) complex 7 and η¹-diphosphene/η²-phosphanylphosphide complex 8, respectively. The latter was characterized by a chloride migration from the palladium atom to a phosphorus atom due to the high electron-accepting character of the PP moiety. Theoretical calculations revealed the migration process and nature of complex 8.

Benzo-Fused Phosphepines: Synthesis by Gold(I)-Catalyzed Intramolecular Hydroarylation and Ring Inversion

Gold(I)-catalyzed intramolecular hydroarylation of dialkynyl(biaryl)phosphine oxides provided versatile benzo-fused phosphepine oxides. O-exo adducts were obtained as the major product, and O-endo adducts were the minor product. O-exo and O-endo indicate the position of an oxygen atom with respect to the central phosphepine framework. The isomers of dibenzo[b,d]phosphepine oxides with methyl and phenyl groups in an adjacent position (shown as 2 a and 3 a in the main text) were determined by X-ray crystallographic analysis. O-exo and O-endo adducts are diastereomers owing to the central chirality of the phosphorus atom and the planar chirality of phosphepine, and they are interconverted through a ring inversion of phosphepine via a transition state with a planar structure. The inversion barrier, fully estimated through theoretical calculations, drastically varied depending on the substituents in the phosphepine framework and/or the fusion of benzene and thiophene rings. Furthermore, the kinetics of the thermal isomerization of less stable O-endo product 3 a into O-exo product 2 a was examined.