Kinetic and Thermodynamic Evaluation of the Reversible N-Heterocyclic Carbene-lsothiocyanate Coupling Reaction: Applications in Latent Catalysis

Abstract

Using stopped flow and other spectroscopic techniques, the thermodynamic parameters of the coupling reaction between 1,3-dimesitylimidazolylidene and phenyl isothiocyanate were determined (H degrees = 96.1 kJ mol(-1) and Delta S degrees = 39.6 J mol(-1) K-1). On the basis of these data which indicated that the reaction was reversible (K-eq = 5.94 x 10(14) M-1 at 25 degrees C; k(r) = 252 M-1 s(-1); k(r) = 4.24 x 10(-13) s(-1)), the adduct formed from the two aforementioned coupling partners was used as a latent catalyst to facilitate the [2 + 2 + 2] cyclotrimerization of phenyl isocyanate and the polymerization of DL-lactide.