P, Se-Heterocycles From the Quasi-Binary System PhP/Se

Abstract

Contrary to statements in the literature the PhP/Se system does contain a compound with a PhP/Se ratio lower than 1. The reaction of pentaphenyl-cyclopentaphosphane and elemental selenium yields depending on the molar ratio the heterocyclic compounds (PhP)₄Se (1), (PhP)₃Se₃ (2), or (PhP)₂Se₄ (3). 1, 2, and 3 are yellow to orange-red crystalline stable compounds. Their molecular structures, as shown by the ³¹P- and ⁷⁷Se-NMR data as well as by the X-ray crystal structure determination of 2, parallel those of the corresponding sulfur derivatives. Nucleophiles add easily to the phosphorus in 3 splitting the P₂Se₂-ring.