STUDIES OF CHEMICAL BONDING USING X-RAY PHOTOELECTRON SPECTROSCOPY

Chemical bonding in a wide variety of inorganic and organometallic systems is studied using x-ray photoelectron spectroscopy. Binding energies of a series of simple compounds of the form RX(,n) can be predicted using a four-parameter equation, where the parameters are indicative of the type of molecule and substituent group. These parameters can also be correlated with lone pair ionization potentials and proton affinities. Carbon 1s binding energies were measured for a series of bis(cyclopentadienyl)metal complexes. Because of the effect on electrostatic potential due to the central metal atom, these binding energies are relatively insensitive to the charge on carbon. Metal binding energies were measured for a series of bis(fulvalene)dimetal complexes. Anomalously low binding energies in two of the complexes can be explained by assuming a lower oxidation state on the metal atoms in these complexes. Phosphorus core electron binding energies were correlated with lone pair ionization potentials and proton affinities for a series of tervalent phosphorus compounds. Examination of the correlations indicates that electronic relaxation associated with core ionization is different from that associated with the other two processes. A new point charge model is described. In this model, partial charges are placed at atomic nuclei, between bonded atoms, and in the lone pair regions of atoms. Binding energies were measured for ((sigma)-C(,3)H(,5))Mn(CO)(,5), ((pi)-C(,3)H(,5))Mn(CO)(,4), and related compounds. Approximate charges on the organic ligands in these compounds could be determined from the binding energies. A method for calculation of proton affinities was developed. The method uses CNDO/2 wave functions and an empirical parameter obtained from experimental proton affinities of test compounds.