Kinetic and Thermodynamic Pathways in the Reactions of Five-Membered Zircona- and Hafnacyclocumulenes with Acetonitrile. Structures and Mechanisms of Formation of the Obtained Complexes

The heating of five-membered zircona- and hafnacyclocumulene complexes (7) with a 2-fold excess of acetonitrile results in the formation of dimeric metallaazacyclopentadiene complexes (6), bicyclic amidine complexes (5), and tricyclic metallacycles (2). These three classes of compounds can be considered as kinetically (6) and thermodynamically (2 and 5) favorable products, the yield of which depends on both the process conditions and the structure of the initial complexes. On the basis of experimental and theoretical data, for all three types of products the reaction proceeds through the formation of monomeric metallaazacyclopentadienes (4) that are competitive.