Addition of H2 O and D2 O to small tungsten suboxide cluster anions Wx Oy- (x=1-4; y3x) was studied using mass spectrometric measurements from a high-pressure fast flow reactor. Within the WO y- mass manifold, which also includes WO4 H-, product masses correspond to the addition of one to three H2 O or D2 O molecules. Within the W2 Oy- cluster series, product distributions suggest that sequential oxidation W2 O y- + H2 O/ D2 O→ W2 O y+1 - + H2 / D2 occurs for y<5, while for W 2 O5-, W2 O6 H2- / W 2 O6 D2- is primarily produced. W2 O6- does not appear reactive. For the W3 O y- cluster series, sequential oxidation with H2 and D2 production occurs for y<6, while W3 O 6- and W3 O7- produce W3 O 7 H2- / W3 O7 D2- and W3 O8 H2- / W3 O8 D 2-, respectively. Lower mass resolution in the W4 O y- mass range prevents definitive product assignments, but intensity patterns suggest that sequential oxidation with H2 / D2 evolution occurs for y<6, while W4 Oy+1 H2- / W4 Oy+1 D2- products result from addition to W4 O6- and W4 O7-. Based on bond energy arguments, the H2 / D2 loss reaction is energetically favored if the new O- Wx Oy- bond energy is greater than 5.1 eV. The relative magnitude of the rate constants for sequential oxidation and H2 O/ D2 O addition for the x=2 series was determined. There are no discernable differences in rate constants for reactions with H2 O or D2 O, suggesting that the H2 and D2 loss from the lower-oxide/hydroxide intermediates is very fast relative to the addition of H2 O or D 2 O.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry