Reaction Mechanisms on [3 + 2] Cycloaddition of Azides with Metal Carbyne Complexes: Significant Effects of Aromaticity, Substituent, and Metal Center

Density
functional theory calculations were used to investigate
the reaction mechanisms on [3 + 2] cycloaddition reactions of azides
with metal carbyne complexes. Our results reveal that the formation
of a 1,4-metallatriazole regioisomer is a kinetically favorable process
in comparison with the formation of 1,5-metallatriazole. Aromaticity
plays an important role in stabilizing the products in these reactions.
Further analyses show that the electron-donating ligand on metal centers
or the electron-withdrawing group on the azide could accelerate the
[3 + 2] cycloaddition reaction. All of these findings could be useful
for experimental chemists to develop “click reactions”
in organometallic chemistry.