Nonbornadiene on Pt(111) is not bound as an n{sup 2}:n{sup 2} diene: characterization of an unexpected n{sup 2}:n{sup 1} bonding mode involving an agostic Pt...H--C interaction
- Univ. of Illinois, Urbana, IL (United States)
- AT&T Bell Lab., Murray Hill, NJ (United States)
The structure and reactivity of norbornadiene (NBD) adsorbed on Pt(111) has been studied by several physical techniques. At 130 K, NBD is bound to the surface in an unusual way: through only one C-C double bond and through an agostic interaction involving one of the C-H bonds of the bridging CH{sub 2} group. The latter interaction is characterized by an intense, broad band centered at 2670 cm{sup -1} (fwhm nearly equals 50 cm{sup -1}) in the RAIR spectra. The data strongly suggest that the other C-C double bond of NBD does not interact with the surface. This unusual binding mode, which may be adopted because steric factors favor it over the alternative {eta}{sup 2}:{eta}{sup 2} geometry, persists to 220-260 K, whereupon the agostic C-H bond is cleaved to give a norbornadienyl intermediate that is stable to 400-450 K. In this latter temperature range the norbornadienyl intermediate decomposes, probably via a retro cyclization reaction, to give benzene and dihydrogen (which desorb) and a fractional monolayer of carbon (which remains on the surface). Comparisons of the low-frequency C-H stretching mode seen for NBD with those seen for other adsorbed hydrocarbons suggest that the line width of these modes is largely due to inhomogeneous broadening, not to dispersion or lifetime effects. 49 refs., 6 figs., 4 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-91ER45439
- OSTI ID:
- 81678
- Journal Information:
- Organometallics, Journal Name: Organometallics Journal Issue: 7 Vol. 14; ISSN ORGND7; ISSN 0276-7333
- Country of Publication:
- United States
- Language:
- English
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