The thermal surface chemistry of iron pentacarbonyl on palladium (111): Reactions of an organometallic on an active metal surface.

摘要

The results presented in this dissertation arise primarily from Fourier transform reflection absorption infrared spectroscopy (FT-RAIRS) and from various methods of Fourier transform mass spectrometry (FTMS). These include thermal desorption spectroscopy (TDS), isotopic-exchange thermal desorption spectroscopy, laser-induced thermal desorption (LITD) using electron ionization, and LITD using chemical ionization via proton transfer or charge exchange. Chapter One provides the general relevance for studying organometallic surface chemistry (i.e., metal-organic chemical vapor deposition for microelectronic materials and surface mediated syntheses for supported metal catalyst generation). Chapter Two describes the ultra-high vacuum surface analysis instrument and some of the experimental methods and operations. Chapter Three presents the FTMS and LITD-FTMS studies of the Fe(CO)₅ vapor and surface-adsorbed phases, respectively, using both electron ionization and chemical ionization. The study demonstrates how one selects a preferred method of ionization, as discussed in Chapter Two. Chapter Four presents coverage dependent, thermal desorption profiles of Fe(CO)₅ on Pd(111), and also presents LITD data as a function of bulk palladium temperature. The rapid heating of LITD provides additional information about the adsorbed reactants and products, beyond that obtained using slower heating. In Chapter Five, the TDS experiment is modified with coadsorbed 13CO or with surface carbon, and the LITD experiment is conducted at higher exposures. The RAIRS results are also presented in Chapter Five and provide great detail concerning the decomposition and reaction mechanism for this system and help support previous interpretations made from the TDS and LITD data.; The significance of this work may be viewed from many perspectives, ranging from fundamental science to applied chemistry, from analytical execution to system-specific chemistries. The identification of decomposition intermediates, reaction products, and possible reaction mechanisms is a system-specific analysis that becomes more fundamental in nature given that the eventual goal is to enhance chemistry's predictive capabilities. Of analytical importance, the research: (1) represents the novel application of LITD-FTMS to a surface-adsorbed organometallic; and (2) incorporates soft-ionization techniques into the LITD experiment. Future applications of this research may involve palladium-mediated synthesis of iron-cluster compounds (relevant to industrial catalysis or waste-stream remediation) or thin or ultra-thin film iron deposition (relevant to microelectronics or magnetic storage devices).