Phosphiranes as Ligands: Tungsten(0) and Palladium(0) Complexes of Phosphirano[1,2-c][1,2,3]diazaphospholes

Asymmetric 1,3-dipolar cycloaddition reaction of chiral 1-alkyl-1,2-diphospholes with diphenyldiazomethane

The 1,3-dipolar cycloaddition of chiral 1-alkyl-1,2-diphosphacyclopenta-2,4-dienes ((1-(−)-menthyl)oxymethyl-1,2-diphosphole and 1-(+)-neomenthyl-1,2-diphosphole) with diphenyldiazomethane leads to novel P-chiral bicyclic phosphiranes having six chiral centers. The degree of diastereoselectivity depends on the substituent at phosphorus, and dramatically increases in the case of (+)-neomenthyl group (de up to 71%). DFT calculations indicate that the cycloaddition is thermodynamically controlled.

The 1,3-dipolar cycloaddition of chiral 1-alkyl-1,2-diphosphacyclopenta-2,4-dienes with diphenyldiazomethane leads to novel P-chiral bicyclic phosphiranes having six chiral centers.

On the nature of M–CO(lone pair)⋯π(arene) interactions in the solid state of fluorinated oxaphosphirane complexes

The X-ray structures of several oxaphosphirane tungsten(0) complexes exhibit interesting intramolecular W–CO(lone pair)ċπ(arene) interactions that have been rationalized by means of high-level DFT calculations and the CSD.

Equilibrium Study of Pd(dba)2 and P(OPh)3 in the Pd-Catalyzed Allylation of Aniline by Allyl Alcohol

Reaction of Pd(dba)₂ and P(OPh)₃ shows a unique equilibrium where the Pd[P(OPh)₃]₃ complex is favored over both Pd(dba)[P(OPh)₃]₂ and Pd[P(OPh)₃]₄ complexes at room temperature. At a lower temperature, Pd[P(OPh)₃]₄ becomes the most abundant complex in solution. X-ray studies of Pd[P(OPh)₃]₃ and Pd(dba)[P(OPh)₃]₂ complexes show that both complexes have a trigonal geometry with a Pd-P distance of 2.25 Å due to the π-acidity of the phosphite ligand. In solution, pure Pd(dba)[P(OPh)₃]₂ complex equilibrates to the favored Pd[P(OPh)₃]₃ complex, which is the most stable complex of those studied, and also forms the most active catalytic species. This catalyst precursor dissociates one ligand to give the reactive Pd[P(OPh)₃]₂, which performs an oxidative addition of nonmanipulated allyl alcohol to generate the π-allyl-Pd[P(OPh)₃]₂ intermediate according to ESI-MS studies.

Reactions of 1-alkyl-1,2-diphospholes with 1,3-dipoles: diphenyldiazomethane and nitrones

The reaction of 1-alkyl-1,2-diphosphacyclopenta-2,4-dienes (1-alkyl-1,2-diphospholes) (1) with diphenyldiazomethane proceeds at room temperature via unstable [3+2] cycloadducts to form bicyclic phosphiranes (2). However, 1-alkyl-1,2-diphospholes (1) react with N,alpha-diphenylnitrone or N-tert-butyl-alpha-phenylnitrone depending on the temperature to give either dimers of 1-alkyl-1-oxo-1,2-diphospholes (5) or 1-alkyl-1,7-dioxo-6-azo-1,7-diphospha-bicyclo[3.2.0]hept-2-enes (7) - phosphorus analogues of β-lactams.