Generation and direct EPR spectroscopic observation of triplet arylphosphinidenes: stabilisation internal rearrangements.

Triplet phosphinidenes, which have been postulated as important intermediates in numerous organophosphorus reactions, have been previously directly observed only in isolated cases. Recently we have published the first recorded EPR spectrum of triplet phosphinidene-mesitylphosphinidene (A. V.

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 -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 EPR Spectrum of Triplet Mesitylphosphinidene: Reassignment and New Assignment.

Low-temperature UV-photolysis of mesitylphosphiranes under highly anaerobic conditions leads to the formation of the triplet mesitylphosphinidene (MesP). The recorded X-band EPR spectrum of triplet MesP and the derived zero-field splitting parameter D=4.116 cm differ significantly from those reported previously for this intermediate.

Mechanism of intramolecular transformations of nickel phosphanido hydride complexes.

In solution, nickel phosphanido hydride complexes ([NiH{P(Ar)(H)}(dtbpe)], Ar = Dmp, Mes*) undergo a degenerate intramolecular exchange, with the Ni-H and P-H hydrogens and both halves of the dtbpe moiety interchanging. This intramolecular rearrangement was shown to occur in three steps: first, the hydride proton migrates to phosphorus, then the P-Aryl moiety rotates around the P-Ni bond, and finally the back migration of one proton to Ni completes the process. Both migration and rotation were determined to be characterized by high barriers (on the NMR time scale) and to depend on the type of aryl group at the terminal phosphorus.

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.