Kinetics of some reactions of cationic organotransition-metal complexes

A general introduction is given to clarify the different ways in which nucleophilic attack on organo transition-metal cationic complexes takes place. Kinetics of the reactions between: [Mn(MeC5H4)(CO)2(NO)]+PF6- and some phosphine ligands were followed by infrared spectroscopy. From the results, a bi molecular mechanism is suggested for this reaction which is confirmed by measuring the activation parameters [equation]. The reaction between (6-phenylhexa-3,5-dien-2-ol) tricarbonyl iron and trifluoroacetic acid was studied kinetically by infrared spectra. The results obtained show that the rate law equation is as follows: Rate = k2[Fe+] [Acid]. N. m. r. spectra for the iron compound and for the product formed with trifluoroacetic acid were recorded at ambient temperature. A proposed mechanism is discussed in the light of both the kinetic and the spectroscopic data. The reaction between [Co(C5H5)(C8H11)]+BF4- and methoxide ion was investigated by stopped-flow techniques over a range of 25-45°C. The plots of Kobs V.OMe- give straight lines with positive intercepts which are interpreted as a parallel reaction with the solvent methanol according to the following mechanism: Rate = {k +K2[OMe-]}[CO]+. The activation parameters were determined for the reaction of cobalt compound with both the methoxide ion and methanol. The structure of the cobalt compound was confirmed by the use of double resonance technique. In the final chapter another kinetic study by stopped flow is described for the reaction between [diagram] and methoxide ion. The reactions were found to proceed through two steps as in [diagram] values of K1, K-1 and K2 were determined, the last being found to decrease in the order Cr> Mo> W. The nature of the intermediate is discussed in terms of correlations between CO stretching force constants in the carbonyl complexes and their tendency to form carbamoyl and carboxyl complexes.