Systematic Structural Coordination Chemistry of <i>p</i>-<i>tert</i>-Butyltetrathiacalix[4]arene:  1. Group 1 Elements and Congeners

Determinations of the crystal structures of complexes of the alkali metal ions with, in the case of Li, the dianion and, in the cases Na−Cs, the monoanion of <i>p</i>-<i>tert</i>-butyltetrathiacalix[4]arene have shown that both the sulfur atoms which form part of the macrocyclic ring, as well as the pendent phenolic/phenoxide oxygen donor atoms, are involved in coordination to these metals. Although the Li and Na complex structures are similar to those of the corresponding complexes of <i>p</i>-<i>tert</i>-butylcalix[4]arene, there is no similarity in the structures of the Cs complexes, with the present structure showing no evidence of polyhapto Cs<sup>+</sup>−π interactions. Instead, the complex crystallizes as a ligand-bridged (S-, O-donor) aggregate of three Cs ions, solvent molecules, and four calixarenes, somewhat like the Rb complex, though here four Rb ions are present, and higher in aggregation than the K<sup>+</sup> complex, where two K<sup>+</sup> ions are sandwiched between two calixarene moieties. The triethylammonium complex of the thiacalixarene monoanion, though formally analogous in that it involves a monocation, has a simpler structure than any of the alkali metal derivatives, based formally on proton coordination (H-bonding). However, interestingly, it can be isolated in both solvated (dmf, dmso) and unsolvated forms, as indeed can the “free”, <i>p</i>-<i>tert</i>-butyltetrathiacalix[4]arene ligand itself.