Insights into Supramolecular Networks Engineered via Tetrel and Hydrogen Bonding Interactions in Hemidirected Lead(II) Complexes

In this study, we explore the role of tetrel bonds (TtBs) and hydrogen bonds (H-bonds) in directing supramolecular crystal packing via self-assembly in two lead(II) chelates: [Pb(tren)(i-mnt)] (1) and [Pb4(tetraen)2(i-mnt)4] (2) [i-mnt -2 = 1,1-dicyanoethylene-2,2-dithiolate, tren = diethylene triamine, and tetraen = tris(2-aminoethyl)amine]. Both complexes were synthesized and isolated, and their solid-state structures were determined through single-crystal X-ray diffraction analysis. The secondary ligands (tren, tetraen) influence the coordination pattern of i-mnt -2 toward the Pb2+ center, generating diverse asymmetric geometries. Complex 1 is a vacant octahedral chelate, while complex 2 is a cocrystalline aggregate of crystallographically independent two cationic [Pb(tetraen)]+2 and two anionic [Pb(i-mnt)2]-2 inversion twins, each displaying seesaw geometry. These hemidirected lead(II) complexes with aliphatic ligands are the first of their class that display PbS, PbN TtB type secondary interactions in self-assembly processes, building homo- and heterodimers. Apart from TtBs, N-HN, N-HS, C-HN, and C-HS type H-bonds also engineer the supramolecular networks, generating diverse chain and ring geometry with requisite stability. DFT calculations and quantum theory of atoms-in-molecules analyses explored the nature of TtBs between hemidirected Pb(II) and the thiolate/cyano end of i-mnt -2 in formed dimers and their pivotal role in stabilizing and elucidating the electronic architecture of dimers. In addition, Hirshfeld surface analysis corroborates with X-ray and DFT results, exploring the existence of TtBs, H-bonds, and other noncovalent interactions that assist in the construction of stable supramolecular networks.