Electron Induced Surface Reactions of the Organometallic Precursor Trimethyl(methylcyclopentadienyl)platinum(IV)

The effect of 500 eV electrons on nanometer scale thick films of trimethyl(methylcyclopentadienyl)platinum(IV) (MeCpPt IV Me 3 ), were studied in situ, under ultrahigh vacuum conditions using a combination of temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), mass spectrometry, and reflection absorption infrared spectroscopy. TPD results revealed the presence of a monolayer state, with a desorption energy >10 kJ mol −1 larger than the multilayer. XPS data indicate that electron beam induced decomposition of adsorbed MeCpPt IV Me 3 produced a carbonaceous film that contained Pt atoms in an electronic state intermediate between metallic Pt and Pt(IV). In addition to Pt(IV) reduction, electron beam irradiation was also accompanied by the evolution of methane and hydrogen from the adsorbate layer and the loss of C−H groups. The rate of Pt(IV) reduction and methane production and the loss of C−H groups from the film were all proportional to the MeCpPt IV Me 3 coverage and the incident electron flux. Rate constants for all three processes were comparable, yielding an average reaction cross section of 2.2 × 10 −16 cm 2 for 500 eV electrons. Changes in the chemical composition of the adsorbate layer as a result of electron beam irradiation were consistent with a process in which one carbon atom desorbs for each MeCpPt IV Me 3 molecule that decomposes. A comparison of the gas-phase products observed during the electron irradiation of adsorbed MeCpPt IV Me 3 and CpPt IV Me 3 support the idea that electron-stimulated decomposition of these platinum precursors involves by Pt−CH 3 bond cleavage.