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Date of Award

1-1974

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Supervisor

D.R. Eaton

Abstract

This work describes the results of a study of phosphine complexes of some selected members of the group VIII transition metal series. The aim of this work was to investigate possible correlations between the electronic properties of these metal complexes and their stabilities and labilities. It was felt that such a study might prove significant since many of the complexes studied are catalytically active in a number of homogeneous systems. Elucidation of the factors influencing the efficiency of such homogeneous catalytic systems is important from both practical and theoretical points of view.

Some electronic properties of the complexes were investigated using a ¹⁹F Nuclear Magnetic Resonance technique. This method is based upon the measurement of the ¹⁹F chemical shifts of complexes of (pFC₆H₄)₃P and (m-FC₆H₄)₃P. The results of this aspect of the work are discussed in Chapter V; i.e., the data is discussed in terms of the "electron affinity" of the central metal.

In order to study the correlation of the "electron affinity" of the central metal with the rates and equilibrium constants for reactions of these complexes, a number of ligand exchange reactions were studied. Chapter III presents the results for such reactions of some palladium(II) phosphine complexes. In the course of this work the formation of four coordinate palladium phosphine cations was demonstrated. The formation of these cations was shown to be highly sensitive to the nature of the particular phosphine used. Chapter IV presents the results for some phosphine ligand exchange reactions of the complexes trans[(C₆H₅)₃Pl₂MCOX (M = Rh and Ir, X = Cl, Br and I) as well as some exchange reactions of the complexes [(C₆H₅)₃P]₃RhX (X = Cl, Br and I). It was shown that the course of these reactions was highly dependent upon the nature of the particular phosphine used in the exchange reaction and on the halide present.

The results described in Chapters III, IV and V are discussed at some length in Chapter VI. In this final chapter, it is argued that the results of the preceeding three chapters can be rationalized in terms of the donor and acceptor properties of the ligands and the acceptor and donor properties of the metal. The results of the ¹⁹ɼ nmr study are used to provide a measure of the acceptor properties of the metal complexes and data from the literature, based primarily on infrared studies are used as a basis for discussion of ligand donor properties. The results presented are consistent with the hypothesis that maximum stability is achieved by optimum matching of ligand donor/acceptor properties with the acceptor/donor properties of the metal.

Chapters I and II are largely introductory. Chapter I includes a brief review of the chemistry of the complexes and ligands discussed in this work. Chapter II gives the basic theories to nuclear magnetic resonance, and conductivity, the two physical techniques used throughout the experimental work reported in this thesis.

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