Designing π-stacking aurones via metalation to square-planar Pd(II)

Square-planar transition metal complexes supported with appropriate ligands can selfassemble via interfacing ligation planes. Here, we present solid-phase (x-ray crystallography) and solution-phase (1 H NMR) data that suggests the monomeric (L1)PdCl units π-stack, e.g. manifesting in dimeric adducts, while corresponding free ligand L1 does not. The x-ray structure of (L1)PdCl suggests that the native π-accepting character of the benzofuranone unit have been amplified by coordination to the Lewis acidic "PdCl." These aggregates also form in solution, with apparent Kdimer ~ 58 M. Main Text: Unique modes of self-assembly will be accessible to square-planar transition metal complexes because they lack apical ligands. Two square-planar coordination planes could πstack with one another if supported with an appropriate ligand, for example. 1-5 However, πstacking refers to a combination of attractive-e.g. electrostatic, dispersion, and donor-acceptor interactions-and repulsive forces-e.g. sterics and Pauli repulsion-for aromatic π-systems; 6-13