A synthesis of the Pd ^II and Pt ^II N,N-diaryldiazabutadiene complexes and their self-assembly into infinite 1-dimensional chains in the solid state via rare C (sp ² )–H … Hal hydrogen bonding is reported. All the new compounds were characterized using elemental analyses (C, H, N), ESI-MS, IR, ¹ H and ¹³ C NMR techniques and X-ray diffraction analysis. The nature and energies of intermolecular non-covalent interactions, which are responsible for the supramolecular polymerization, were studied theoretically using DFT calculations and topological analysis of the electron density distribution within the formalism of Bader's theory (QTAIM method). While chloro-complexes, which feature a relatively stronger C (sp ² )–H … Hal hydrogen bonding, form supramolecular polymers, the iodo-derivative does not self-assemble into 1-D chains due to the dominance of other crystal packing forces over the potential H⋯I contacts. Thus, the C (sp ² )–H … Hal HB can dictate a packing preference in the solid state and serve as a useful tool for supramolecular engineers.