The tetrel bonding role in supramolecular aggregation of lead(II) acetate and a thiosemicarbazide derivative.

Abstract

A new Pb^II coordination complex [PbL(OAc)], which was readily synthesized from a mixture of Pb(OAc)₂·3H₂O and 1-(pyridin-2-yl)benzylidene-4-phenylthiosemicarbazide (HL) is reported. The crystal structure analysis of [PbL(OAc)] showed that the Pb^II cation is N,N',S-chelated by the tridentate pincer-type ligand L and by the oxygen atoms of the acetate anion. In addition, the metal centre forms Pb...O and Pb...S tetrel bonds with an adjacent complex molecule, yielding a 1D zigzag polymeric chain, which is reinforced by N-H...O hydrogen bonds and π...π interactions. These chains are interlinked by C-H...py non-covalent interactions, realized between one of the acetate hydrogen atoms and the pyridine rings. According to the Hirshfeld surface analysis, the crystal packing is mainly characterized by intermolecular H...H, H...C and H...O contacts, followed by H...N, H...S, C...C, C...N, Pb...H, Pb...O and Pb...S contacts. The FTIR and ¹H NMR spectra of [PbL(OAc)] testify to the deprotonation of the parent ligand HL, while the acetate ligand exhibits an anisobidentate coordination mode as established by means of single-crystal X-ray diffraction and FTIR spectroscopy. Lastly, theoretical calculations at the PBE0-D3/def2-TZVP level of theory have been used to analyze and characterize the Pb...O and Pb...S tetrel bonds observed in the crystal of [PbL(OAc)], using a combination of QTAIM (Quantum Theory of Atoms in Molecules) and NCIPlot (Non-Covalent Interaction Plot) computational tools.