The migratory insertion of carbon monoxide and methyl isocyanide into zirconium-carbon and titanium-carbon bonds anchored to a calix[4]arene moiety: A dynamical density functional study

The energetics and reaction mechanism of the migratory insertion of carbon monoxide and methyl isocyanide into the zirconium-carbon and titanium-carbon bonds in [calix[4](OMe)(2)(O)(2)-M-Me-2], (M = Zr, TO, have been investigated by combining static and dynamic density functional calculations. Two steps have been characterized: the coordination of the incoming nucleophilic moiety leading to relatively stable facial adducts; its subsequent insertion into the M-C bond, leading to eta(2)-bound acyl or iminoacyl complexes, providing a rationale for the different behavior of CO and MeNC towards both insertion and deinsertion reactions. Our results indicate that the rate-determining step for the overall MeNC insertion into the M-C bond is its coordination to the electron-deficient metal center, with the titanium system featuring a higher energy barrier (12.7 versus 5.5 kcal mol(-1)). Ab initio molecular dynamics simulations have been performed on the Zr system by means of the Car-Parrinello method, to study the hitherto inaccessible mechanistic features of the insertion reactions.