Designing for Intramolecular H-Bonding in Palladium(II) Dichlorides

Establishing an intramolecular H-bond requires a conformational rearrangement. Here, we apply principles from conformational analysis to design intramolecular H-bonding in square-planar Pd(II) dichlorides. Comparisons between diprotic (<b>L1</b>)PdCl₂ and monoprotic analogues, (<b>L2</b>)PdCl₂ and (<b>L3</b>)PdCl₂, illustrate that unsaturated six-membered metallacycles are well-suited to "flex" and accommodate intramolecular H-bonding. Analyzing the individual H-bonds with a distortion-interaction model suggests that this flexibility originates from small energies of rearrangement. Our analysis unifies other cases of intramolecular H-bonding under a common framework.