STUDY OF THE GEOMETRICAL STRUCTURE AND THE VIBRATIONAL-SPECTRA OF P4O8, P4O6S2, AND P4O6SE2

In the present work the bonding situation within the P4O6X2 (X = O, S and Se) series is analysed by means of the geometrical structures and the IR spectra of those molecules. The experimental data are obtained from pure P4O8 and P4O6Se2 crystals which could be synthesized for the first time. The theoretical geometrical structures were obtained by e mploying the Hartree-Fock method in combination with a basis set of do uble zeta quality plus polarization functions. Theoretical vibrational spectra calculated with the same method were refined by using the Sca led Quantum Mechanical method proposed by Pulay. Our study shows that the doubly substituted compounds behave very similar to the monosubsti tuted molecules, e. g. shifts of the vibrational frequencies result ma inly from the differences in the bond strengths of the P = X units and the different masses of the substituents, while the bonding situation within the P4O6 frame remains nearly unchanged within this series.