Physical Organic Chemistry of Transition Metal Carbene Complexes. Part 20: 1 Kinetics and Mechanism of Reactions of (CO) 5 M C(OMe)C 6 H 4 X (M=Cr and W) with Primary Aliphatic Amines in Aqueous Acetonitrile. Substituent Effects

摘要: Abstract A kinetic study of the reactions (CO)5Cr C(OMe)C6H4X (X=4-Cl, 4-F, H, 4-Me, 4-OMe and 4-NMe2) respective tungsten carbene complexes with primary aliphatic amines (mainly n-butylamine) in 50% MeCN–50% water (v/v) at 25°C is reported. The rate law complex shows OH− amine catalysis low concentrations but not high concentrations. results are consistent a three-step mechanism: first step nucleophilic addition to form zwitterionic steady state intermediate, TA±, which, second step, followed by rapid deprotonation TA± anionic intermediate TA−, while third involves RNH3+ catalyzed methoxide ion expulsion, respectively, substitution product, (CO)5M C(NHR)C6H4X (M=Cr or W). It shown that limiting and/or reasons why TA− cannot be observed directly discussed detailed analysis substituent effects on various parameters presented.