Vinyl-Acetamidination of in Situ-Generated Acetylenic Complexes of Zirconocenes: Thermal Isomerization of Obtained Zirconabicycles

The interaction of seven-membered zirconacyclocumulene 1 and zirconacyclopentadiene 9 complexes of zirconocene with a twofold excess of acetonitrile results in the formation of vinyl-acetamidine zirconabicycles 7 and 11. Both reactions proceed via the intermediate generation of the acetylene complexes of zirconocene and the subsequent vinyl-acetamidination of these complexes with the formation of final complexes 7 and 11. The reaction of dimeric zirconaazacyclopentadiene metallacycle 2 with 1 equiv of acetonitrile at 100 °C in toluene also results in the formation of complex 7. The obtained complex 7 is capable of undergoing unusual thermal isomerization with the formation of a strained triheterocyclic complex 8 containing a T-shaped pyrrole carbon atom. This isomerization proceeds even in the absence of any solvent with an almost quantitative yield at 140 °C for 45 h. The structures of 7, 8, and 11 have been determined by X-ray diffraction. © 2022 American Chemical Society. All rights reserved.