Hans-Peter Baldus

Phosphorus-31 and selenium-77 nuclear magnetic resonance spectra of phosphorus-poor phosphorous selenide compounds

The compounds P3Se4X (X = I, Br, Cl, SC2H5, SC5H11 or SC6H5) have been made as phosphorus-poor analogues of the corresponding compounds α- or β-P4E3X2(E = S or Se), in which a PX unit has been replaced by Se. Analysis of 31P and (in part)77Se NMR spectra of the P3Se4X compounds has shown remarkable correspondence of the coupling constants and chemical shifts between the P3Se4X and α-P4S3X2 series of compounds. Phosphorus-31 and 77Se NMR spectra of α-P4Se3I2 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 = I, Br or Cl), by skeletal rearrangement on the NMR time-scale, has been studied at several temperatures, yielding kinetic data.