Several mechanisms proposed and calculated for the sequential oxidation of tungsten suboxide clusters by H 2 O/ D 2 O [Mayhall, J. Chem. Phys. 131, 144302 (2009)] are evaluated using anion photoelectron spectroscopy of an apparent intermediate, W 2 O 6 D 2 -. The spectrum of W 2 O 6 D 2 -is consistent with the W 2 O 5 - + D 2 O→ W 2 O 6 - + D 2 intermediate in which the initial water addition involves the interaction of the oxygen from D 2 O with a tungsten atom, approaching from a direction with the least repulsion from the W 2 O 5 - oxygen atoms, coupled with the interaction between a deuterium with a tungsten-tungsten bridging oxygen on the cluster. The presence of W 2 O 6 H 2 - and W 2 O 6 D 2 - suggests that there is insufficient internal energy in the complex to surmount the barrier for rearrangement required for tungsten hydride and hydroxide formation necessary for H 2 or D 2 evolution, which was calculated to be energetically favorable. The quality of the calculations is verified by direct comparison between experimental photoelectron spectra of W 2 O 5 - and W 2 O 6 - and spectral simulations generated from the lowest energy structures calculated for W 2 O 5 -, W 2 O 6 - and their corresponding neutrals. The results shed light on the importance of repulsion on the pathway a reaction follows under room temperature conditions.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry