Transition metal carbene chemistry. Kinetic studies on the reactions of [methyl(thiomethoxy)carbene]pentacarbonylchromium(0) with morpholine in aqueous acetonitrile—a kinetic evaluation of pKaCH

摘要: A kinetic study of the aminolysis [methyl(thiomethoxy)carbene]pentacarbonylchromium(0), (CO)5CrC(CH3)(SCH3) (2-Cr), with morpholine, a secondary amine, in 50% acetonitrile–50% water (v/v) at 25° C is reported. The second-order rate constant (kA L mol−1 s−1) increases amine concentration, giving linear dependence an intercept on axis. general base-catalyzed nature reaction was confirmed by both and hydroxide ion concentrations. mechanism proposed very similar to those for ester reactions, involving nucleophilic addition substrate yield zwitterionic tetrahedral intermediate (TA#), followed deprotonation TA# form TA− fast step, which, third converted product acid-catalyzed thiomethoxide expulsion. As carbene itself acts as acid only active towards protic equilibrium evaluated through morpholine found be good agreement value reported earlier.