Mechanistic Study and Ligand Design for the Formation of Zinc Formate Complexes from Zinc Hydride Complexes and Carbon Dioxide

Density functional theory (DFT) study
of the reactions of mononuclear
phenolate diamine zinc hydride complexes and CO2 reveals
a direct insertion mechanism with a rate-determining C–H bond
formation step. A total of 16 zinc hydride complexes with various
functional groups, including 3 experimental structures and 13 newly
proposed complexes, have been optimized. The influences of various
substituents at different positions, the ring size of nitrogen bidentate
ligands, and the ortho groups of nitrogen on the reaction rate are
investigated. Computational results indicate that the ortho effect
of nitrogen is the most effective factor in reducing the reaction
energy barrier, and the complex with isopropyls as the ortho groups
of the nitrogen atom has the lowest barrier of 10.9 kcal/mol.