Theoretical Study on Iridacycle and Rhodacycle Formation via C–H Activation of Phenyl Imines

A computational
study with the Becke3LYP DFT functional was carried
out on the formation of iridacycles and rhodacycles through C–H
activation of phenyl imines in methanol solvent. The whole catalytic
pathway was proposed and verified, starting from the catalyst [Cp*MCl2]2 cleavage and ending with the cyclometalated
complex. The five most important issues, namely, chloride dissociation
and C–H activation precursor formation, aromatic C–H
bond activation, the reaction rate difference between the Ir and Rh
systems, the nature of regioselectivity, and the role of the protic
solvent are discussed. The calculations indicate that the C–H
bond activation by the transition metal iridium is kinetically and
thermodynamically more favorable than that by rhodium, and the regioselectivity
of the reaction has been determined both electronically and sterically.