| Περίληψη: | <p>This thesis describes the measurement of stability constants for olefins with tetrachloroplatinate(II) and silver(I) ions. The two systems studied were</p> <p align="center">ol + PtCl<sup>=</sup><sub style="position:relative;left:-.6em">4</sub>&leftrightharpoons;(ol)PtCl<sup>−</sup><sub style="position:relative;left:-.5em">3</sub> + Cl<sup>−</sup></p> <p align="center">and</p> <p align="center">ol + Ag(H<sub>2</sub>O)<sup>+</sup><sub style="position:relative;left:-.5em">n</sub>&leftrightharpoons;(ol)Ag(H<sub>2</sub>O)<sup>+</sup><sub style="position:relative;left:-.6em">m</sub></p> <p>where ol = olefin. The olefins studied were either unsaturated ammonium salts or unsaturated alcohols.</p> <p>With platinum(II) , it is found that olefins give higher stability constants than water, lower than amines and comparable with the heavier halides. With silver (I), olefins give stability constants lower than amines and the heavier halides, but comparable to water and fluoride.</p> <p>In the case of platinum(II) , enthalpy and entropy values were obtained from the temperature dependence of the stability constants. It was found that the overall stability constant was strongly dependent on the entropy change. The variation in the entropy change is ascribed largely to variations in the solvation energies of the ligands and complexes.</p> <p>Comparison of the enthalpy values for different olefins shovs four main trends.</p> <p><ol><li>There is an increase in ΔH from allX<sup>+</sup> to butX<sup>+</sup>(X a NH<sub>3</sub>, NEt<sub>3</sub> and AsEt<sub>3</sub>).</li> <li>There is an increase in ΔH in the series allX<sup>+</sup> where X = Net<sub>3</sub>, NMe<sub>3</sub>, NHEt<sub>2</sub>, NH<sub>2</sub>Et and NH<sub>3</sub>.</li> <li>There is an increase in ΔH for allY on replacing Y=NH<sup>+</sup><sub style="position:relative;left:-.5em">3</sub> by Y=OH.</li> <li>There is a decrease in ΔH in the series CH<sub>2</sub>=CH-CH<sub>2</sub>-NH<sup>+</sup><sub style="position:relative;left:-.5em">3</sub>,CH<sub>2</sub>=CH-CH(CH<sub>3</sub>)-NH<sup>+</sup><sub style="position:relative;left:-.5em">3</sub> and trans-CH<sub>3</sub>-CH=CH-CH<sub>2</sub>-NH<sup>+</sup><sub style="position:relative;left:-.5em">3</sub>.</li></ol></p> <p>Trends 1. and 2. can be explained in terms of an inductive effect. Both trends indicate that the π-acceptor capacity of the olefin is more important than the δ-donor capacity for the formation of stable platinum-olofin bonds. Trend 3. is shown to be largely the result of solvation energy changes. Trend 4. is shown to result from a combination of steric and inductive effects.</p> <p>It was found that the stability constants for silver(I)-olefin complexes are much lover than for platinum(II)-olefin complexes. This can be explained in terms of the nature of the metal-olofin bond in the two series of complexes. It was also found that silver(I) showed a much greater preference than platinum(II) for the uncharged alcoholic ligands rather than the positively charged ammonium ligands. This can be explained in terms of the electrostatic interaction between the positively charged ammonium group and the central metal group.</p> <p>From a study of the ultra-violet spectra of the platinum(II)-olefin complexes, it is shown that the relative energies of the d-orbitals in these complexes are d<sub>x</sub>2<sub>-y</sub>2>d<sub>xy</sub>>d,sub>z</p>2>d<sub>yz</sub>>d<sub>xz</sub>.
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