Thallium(i)phosphorodithioates containing intra- and intermolecular π-hole triel bonds

Abstract

Thallium compounds, i.e. Tl⁺[S₂P{OC₆H₃(2,5-(CH₃)₂)}₂]⁻ (1) and Tl⁺[S₂P{OC₆H₃(3,5-(CH₃)₂)}₂]⁻ (2), stabilized by intra- and intermolecular triel bonds were isolated and characterized by FT-IR, NMR (³¹P, ¹H and ¹³C) spectroscopy, and SC-XRD analysis. The crystal structures of 1 and 2 belong to monoclinic crystal systems with the space group C2/c and P2₁/n, respectively. Interestingly, the positively charged Tl atom is bonded attractively with the π-holes of the 1,1-dithioate moiety. These compounds exist in ionic form and exhibit Tl⋯S and Tl⋯π contacts (TrBs), which assist the formation of unique supramolecular polymeric architectures owing to the stereochemically active lone pair of electrons and hemi-directed coordination sphere around thallium. A differentiating feature in compound 2 is the formation of a unique Tl⋯π/π⋯π/Tl⋯π self-assembly. The attractive nature of TrB was further confirmed by DFT calculations using the quantum theory of atoms-in-molecules (QTAIM) and non-covalent interaction plot (NCIPlot) index methods. A systematic Hirshfeld surfaces analysis was also carried out to compare the intermolecular interactions.