Interconversion of Metallanaphthalynes and Indenylidene Complexes: A DFT Prediction

Metallaaromatics
have attracted considerable interest of both theoretical
and experimental chemists. However, there have been only two metallanaphthalynes
isolated so far. Thus, developing new synthetic approaches is urgent.
Here we present thorough density functional theory (DFT) calculations
on the thermodynamics and kinetics of the isomerization between metallanaphthalynes
and metal indenylidene complexes. The effects of metal centers, ligands,
and substituents on the metallabicycles were examined systematically.
Our results reveal that, in comparison with the third-row transition
metals, the second-row metals have a tendency to form metal indenylidenes
rather than metallanaphthalynes. In addition, π-donor and π-acceptor
ligands can stabilize the metallanaphthalynes and indenylidene complexes,
respectively. Steric effects at the meta position also play a role
in the stabilization of metallanaphthalynes. Electron-donating groups
(EDGs) at the meta position and second-row transition metals give
lower barriers in comparison with electron-withdrawing groups (EWGs)
and third-row transition metals. Finally, an interconversion of osmanaphthalynes
and indenylidene complexes was achieved by simply tuning the substituents
on the metallabicycles. Therefore, our findings open an avenue to
metal indenylidene complexes and metallanaphthalynes.