THE ANALYSIS OF COORDINATION COMPOUNDS AND ORGANOMETALLICS BY X-RAY PHOTOELECTRON SPECTROSCOPY AND SECONDARY ION MASS SPECTROMETRY
Abstract
Two surface sensitive techniques, viz., x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS), have been applied to the analysis of bulk inorganic materials. An XPS study on the parent complexes Fe(,2)(CO)(,6)(PPh(,2))(,2), Fe(,3)(CO)(,9)(PPh)(,2) and Co(,4)(CO)(,10)(PPh)(,2) and derivatives obtained by the substitution of CO by PPh(,3) or P(OMe)(,3) has demonstrated the correlation between the electronic structure of the phosphorous atom, discernible by XPS, and its chemical reactivity. The W 4f binding energies have been measured for a series of complexes containing the {(eta)('3)-allyl)W(CO)(,2)} unit and neutral derivatives of the type W(CO)(,6-x)L(,x). No correlation was observed between the metal binding energies and the value of x in the W(CO)(,6-x)L(,x) series. These results have been compared with available data for the analogous molybdenum systems. The application of SIMS to the direct analysis of preformed, well-defined coordination compounds such as {Co(en)(,2)Cl(,2)}NO(,3), Mo(,2)(O(,2)CCH(,3))(,4), Cu(thiourea)(,2)Cl(,2), and Ni(PR(,3))Cl(,2) and organometallics such as ((eta)('5)-Cp)(,2)TiCl(,2) has been investigated. The resulting mass spectra contain ions characteristic of molecular weight and structurally diagnostic fragments. An indepth study of transition metal isocyanide complexes revealed that for stable monocations such as {Cr(NO)(CNR)(,5)}(PF(,6)) or dications such as {Cr(NO(CNR)(,5)}(PF(,6))(,2) which may be readily reduced to a stable singly-charged species, SIMS spectra characteristic of the complex can be obtained. However, for complexes such as {Cr(CNR)(,6)}(PF(,6))(,2) which do not possess stable monocationic counterparts, no structurally diagnostic ions are obtained. These trends are discussed in light of the "18-electron" rule. A detailed study on the clustering observed for metal acetylacetonates of the type M(acac)(,3) (M = Cr, Mn, Fe and Co), is presented and the laser desorption spectra of several of these complexes are discussed. A preliminary study of Ni{P(OR)(,3)}(,4) and Ni(PR(,3))(,2)Cl(,2) complexes supported on silica and alumina is presented. The potential of SIMS for application to supported catalysts is demonstrated. Correlations between structure and spectra as developed in these studies aid in the definition of surface structure on a scale particularly appropriate to catalysis research.
Degree
Ph.D.
Subject Area
Chemistry
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