Thiacalix[4]arenes: Extraction of palladium and the electronic structure

The extractability of palladium nitro complexes with the charge state of sulfur and oxygen atoms in thiacalix[4]arenas in the cone and 1,3-alternate conformations are compared. The results of X-ray photoelectron and X-ray emission studies indicate the presence of considerable electron density on the bridging sulfur atoms, which is due to the contribution of the sulfur 3p AO to the upper occupied MOs of molecules. A series of changes in the electron density on sulfur atoms in the order calixarene thioethers > thiacalixarenes > dialkylsulfides ((C₁₀H₂₁)₂S) > (C₆H₅)₂S not completely coincide with changes in their extrability, which can be caused by different nature and stoichiometry of the formed palladium complexes.