η3-allyl-Pd(II) complexes of 2-, 3- and 4-pyridylmethyl-coumarin esters

Abstract

A series of 2-, 3- and 4-pyridylmethyl-coumarin esters ligands (1–3) and their η³-allyl palladium complexes (1-Pd–3-Pd) have been designed, synthetized, and characterized. NMR analysis of compounds 1-Pd–3-Pd indicated the presence of the allyl fragment. The molecular structures of 2, 3 and 1-Pd were determined by X-ray crystallographic analysis. The molecular structure of 1-Pd reveals that coumarin ligand (2) is coordinated to the palladium center via a monodentate fashion through the nitrogen atom of the pyridinyl fragment while, the allyl group is binding via a η³ fashion in an overall square-planar geometry completed with a chloride atom. The crystal packing is stabilized by a variety of weak intermolecular conventional and non-conventional interactions involving C–H–O/N hydrogen bonds, π–π and C–H–π interactions, which have been analyzed by Hirshfeld surface and non-covalent interactions analysis. The intermolecular interaction energies were explored using an energy framework analysis, which revealed that π–π and C–H–π interactions serve as the primary building blocks in these crystal packing.

Graphical abstract