Structure and Rearrangements of 7-(Heptaphenylcycloheptatrienyl)isochalcogencyanates

Abstract

According to DFT B3LYP/6-31G(d,p) calculations, the intramolecular migration of NCX groups (X = O, S, Se, Te) in 7-(heptaphenylcycloheptatrienyl)isochalcogencyanates in the gas phase proceeds via the dissociation–recombination mechanism. Structures were found of transition states preceding the formation of tight ion pairs. High activation barriers to the migration of isochalcogencyanate groups (\(\Delta E{^\neq_{\rm{ZPE}}}\) 26.7, 21.3, 20.5, 19.3 kcal mol^–1) originate from the existence of stable conformation of molecules with NCX groups located in the equatorial position and are in agreement with the data of dynamic NMR. For the transition of the molecule in the form favorable for the NCX group migration an inversion of the seven-membered ring and the rotation of the phenyl group are necessary.