Density functional studies on diimine chelated palladium complex catalyzed Suzuki-Miyaura cross-coupling reaction: the impact of Lewis base employed in transmetallation process.

The transmetallation processes of disubstituted diimine (RN=CH-CH=NR) chelated palladium complexes catalyzed Suzuki-Miyaura cross-coupling reactions of phenyl chloride (PhCl) and phenylboronic acid [B(OH)(2)Ph] in the presence of diverse Lewis bases (OH(-), F(-), O(t)Bu(-), CO(3)(2-) and PO(4)(3-)) were studied by DFT methods with the B3LYP functional. Activation strain model has also been employed to investigate the extent of deformation of the reactants including the catalyst in the transition state. The transmetallation processes for all the cases are exothermic. The energy barriers for the process with multivalent bases are smaller than that of univalent cases, while, the amounts of the released energies are on the opposite course. The high valent oxoanions such as CO(3)(2-) and PO(4)(3-) provide more versatile bonding modes in the processes. The flexibility of diimine either as mono- or bi-dentate ligand in the mechanism provides a valuable channel for lowering the energy barriers of this process. The simplicity and efficiency of this type of ligand make it a potential alternation to the most commonly used phosphine.