Bond Dissociation Energies of Tungsten Molecules: WC, WSi, WS, WSe, and WCl.

Abstract

Resonant two-photon ionization spectroscopy was used to locate predissociation thresholds in WC, WSi, WS, WSe, and WCl, allowing bond dissociation energies to be measured for these species. Because of the high degree of vibronic congestion in the observed spectra, it is thought that the molecules dissociate as soon as the lowest separated atom limit is exceeded. From the observed predissociation thresholds, dissociation energies are assigned as D0(WC) = 5.289(8) eV, D0(WSi) = 3.103(10) eV, D0(WS) = 4.935(3) eV, D0(WSe) = 4.333(6) eV, and D0(WCl) = 3.818(6) eV. These results are combined with other data to obtain the ionization energy IE(WC) = 8.39(9) eV and the anionic bond dissociation energies of D0(W-C-) = 6.181(17) eV, D0(W--C) = 7.363(19) eV, D0(W-Si-) ≤ 3.44(4) eV, and D0(W--Si) ≤ 4.01(4) eV. Combination of the D0(WX) values with atomic enthalpies of formation also provides ΔfH0K° values for the gaseous WX molecules. Computational results are also provided, which shed some light on the electronic structure of these molecules.