Studies in metallocene chemistry: A cell for infrared spectroelectrochemistry with applications in titanocene chemistry, ferrocene-containing polyesters, substituent effects in cyclopentadienylrhodium compounds

Studies of the properties of metal cyclopentadienyl compounds were made by infra-red spectroelectrochemistry, electrochemistry, synthesis and $\sp{103}$Rh nuclear magnetic resonance spectrometry. A cell capable of simultaneously recording IR spectra of the region near the electrode surface during electrochemical experiments was developed, and characterized using ferricyanide. The absorbance-time response to potential step and potential sweep experiments was investigated and the experimentally determined response compared to a digital simulation of the response at different distances from the electrode surface. This allowed the distance from the electrode surface to the point of observation to be estimated. The capabilities of the cell were applied to the elucidation of the electrochemical behavior of titanocene dichloride and iron pentacarbonyl. Titanocene dichloride was reduced under an atmosphere of carbon monoxide to titanocene dicarbonyl and ultimately to the anion (CpTi(CO)$\sb4$) $\sp{-}$. No evidence for the formation of a titanium(III) carbonyl species was found. In contrast, reduction of titanocene dichloride in the presence of 2,6-dimethylphenylisocyanide led to the formation of titanium(III) and titanium(II) products, in which one and both of the chloride ligands had been replaced by the isocyanide, respectively. Electrochemical and chemical reduction of fulvalene-dititanium cyclopentadienyl compounds led to the breakage of the carbon-carbon bond linking the two five-membered rings of the fulvalene ligand. The electrochemical properties of a series of ferrocene-containing polyesters in solution was investigated using various stationary and rotating solid electrode techniques. The oxidised form of the polyesters coated the electrode surface in an uneven fashion allowing solution and surface processes to occur simultaneously. Evidence for the nature of this coating was gathered using X-ray photoelectron spectroscopy. The effect of substituents on a series of ring-substituted (h$\sp5$-cyclopentadienyl)dicarbonylrhodium complexes was investigated by means of changes in C-O stretching frequencies as well as $\sp{103}$Rh NMR chemical shifts. The effect of the substituents was found to be neither a purely resonance or inductive phenomenon, but best described by a substituent parameter which took both effects into account