AN AB-INITIO STUDY OF THE ELECTRONIC-STRUCTURE AND RELATIVE STABILITYOF THE HALOGENATED THIOPHOSPHORUS COMPOUNDS SPX (X = CL, F, BR) AND THEIR ISOMERS

The electronic structure and relative stability of the halogenated thi ophosphorus compounds SPCl, SPF, and SPBr and their isomers ClSP, FSP, and BrSP were investigated using ab initio post-Hartree-Fock methods. Molecular geometries of all these structures together with the transi tion states between isomers, have been optimized at the SCF, MP2, and CCSD levels. Single-point CCSD(T) and MP4 calculations have been perfo rmed at the optimal CCSD and MP2 geometries. All calculations have bee n done using the standard 6-311G(2d) basis set. Harmonic vibrational f requencies and IR intensities for all species were calculated at the c orrelated levels, and they are in good agreement with the available da ta from matrix-isolated TR spectroscopy. Because the isomers ClSP, FSP , and BrSP have not yet been experimentally observed, we extended our study by calculating of equilibrium constants of isomerization using E yring transition state theory, and we have found that at sufficiently high temperatures (approximate to 1000 K) the equilibrium constants ar e large enough for the possible detection of these isomers. (C) 1997 E lsevier Science B.V.