P-31 AND SE-77 NUCLEAR-MAGNETIC-RESONANCE SPECTRA OF PHOSPHORUS-POOR PHOSPHORUS SELENIDE COMPOUNDS

Abstract

The compounds P3Se4X (X = l, Br, Cl, SC2H5, SC5H11 or SC6H5) have been made as phosphorus-poor analogues of the corresponding compounds alpha- or beta-P4E3X2 (E = S or Se), in which a PX unit has been replaced by Se. Analysis of P-31 and (in part) Se-17 NMR spectra of the P3Se4X compounds has shown remarkable correspondence of the coupling constants and chemical shifts between the P3Se4X and alpha-P4S3X2 series of compounds. Phosphorus-31 and Se-77 NMR spectra of alpha-P4Se3l2 are reported for comparison. Further replacement of a PX unit by Se gives the ultimate phosphorus-poor cluster compound P2Se5, for which a synthesis from the elements and full NMR data are reported. This sought after higher selenide of phosphorus is thus a phosphorus-poor molecule with concatenated selenium, rather than a selenium-rich structure with exocyclic selenium. The interconversion of optical isomers of the P3Se4X halides (X = l, Br or Cl), by skeletal rearrangement on the NMR time-scale, has been studied at several temperatures, yielding kinetic data.