A semiempirical approach toward the origin of f-element binding selectivity of pyridine-2,6-diylbis(diphenylphosphine oxide)

The geometries of a series of lanthanide complexes with phosphine oxide-type ligands (either mono- or polydentate) were optimized using the PM6/Sparkle semiempirical computational approach. The activation barriers of coordination reactions (i.e. the conversion of a complex with κ¹-bound ligand into a complex with multiply bound one) were estimated. The κ²-chelate formation with a pyridine-2,6-diylbis(diphenylphosphine oxide) ligand is favorable only for a few largest lanthanides, while κ¹-coordination is the most probable case for the smaller ones.