Metal Complex Catalysed Reactions of Anils

Abstract

<p>It has been found that a series of thiourea metal complexes are very efficient catalysts for a number of reactions involving anils. These reactions, the formation and hydrolysis of the anil and a transimination reaction, were studied using acetone and various substituted anilines as substrates. The catalysts were Co(II) and Zn(II) complexes of thiourea and substituted thioureas and were found to have a wide range of effectiveness as catalysts.</p> <p>Kinetic studies have been carried out using a number of NMR techniques, including measurement of initial rates by integration, line broadening studies and spin saturation transfer (SST) experiments. Equilibrium constants for association of various substrates with the catalysts have also been determined, taking advantage of the paramagnetism of the Co(II) complexes.</p> <p>The results indicate that the rate determining step for the formation of the anil involves nucleophilic attack of aniline on coordinated acetone. The aniline in this case is the second coordination sphere of the metal complex and the acetone is in the first analogous mechanisms. The utility of SST experiments is demonstrated by the identification of the transimination reaction and the measurement of two exchange processes in this reaction.</p>