A comparative study of PF 3, PH 3 and P(CH 3) 3 on clean, K-covered, and Cl-covered Ag(111)

Abstract

Abstract The adsorption and desorption of PF3, PH3 and P(CH3)3 on clean, K-covered, and Cl-covered Ag(111) has been studied using temperature programmed desorption (TPD), work function change measurement (Δφ), ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). All three compounds adsorb molecularly at 105 K, adsorb through their P atoms, and desorb reversibly with no detectable decomposition. The adsorptions are accompanied by a maximum surface work function change of −0.15 eV (PF3), −1.4 eV (PH3) and −2.45 eV (P(CH3)3). The desorption energies increase in the order PF3 E d = 7.5 kcal mol . For PH3 and P(CH3)3, there appear to be strong repulsive adsorbate-adsorbate interactions. The bonding modes of PH3 and P(CH3)3 only involve σ-donation. For PF3, σ-donation and π-back-donation are involved. TPD and Δφ measurements indicate that the σ-donation capability follows the order P(CH3)3 > PH3 > PF3. This order is directly related to the electronegativity of the group attached to the phosphorus. Δφ, UPS and XPS measurements indicate that there is some structural rearrangement taking place in the multilayer P(CH3)3 when the surface temperature is increased. Surface Cl stabilizes adsorbed PF3, PH3 and P(CH3)3. Surface K also stabilizes PF3, but destabilizes PH3 and P(CH3)3. We compare our results with the corresponding coordination chemistry.