Geometric control of Cu, Ni and Pd complexes in the solid state via intramolecular H-bonding interactions

In this article, we describe the synthesis and characterization of a family of copper, nickel and palladium complexes bound by bidentate ligands derived from ortho-phenylenediamine that contain tunable H-bond donors. The crystal structures of the reduced dianionic metal complexes (formulated as [MII(L2-)2]2-) depict intramolecular H-bonding interaction between the two ligand scaffolds. Variations on the primary (Cu, Ni, Pd), secondary (H-bonding donor) and tertiary coordination sphere (solvent of crystallization and countercation), led to the isolation of the metal complexes in square-planar (SP) and/or twisted pseudo-tetrahedral geometry (TW). A detailed structural analysis of the complexes in the solid state revealed that the intramolecular H-bonding interactions can be altered by disrupting the bonds between the countercation, solvent of crystallization and the ligand scaffold, which leads to changes in the geometry of the complexes (SP or TW). DFT calculations are in agreement with our experimental observations, in which the Cu complexes were found to favor twisted geometries while the Ni and Pd complexes favored square-planar geometries.

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In this article, the synthesis and characterization of copper, nickel, and palladium complexes bound by bidentate ligands derived from ortho-phenylenediamine are described. The complexes contain tunable H-bond donors and their crystal structures reveal intramolecular H-bonding interactions between the ligand scaffolds. Variations in the coordination sphere led to the isolation of the complexes in square-planar or twisted pseudo-tetrahedral geometries. Structural analysis showed that intramolecular H-bonding interactions can be altered by disrupting the bonds between countercations, solvent of crystallization, and ligand scaffold, resulting in changes in the geometry of the complexes. DFT calculations confirmed that Cu complexes prefer twisted geometries while Ni and Pd complexes favor square-planar geometries.