| Abstract
| - Determinations of the crystal structures of complexes of the alkali metal ions with, in the case of Li, the dianionand, in the cases Na−Cs, the monoanion of p-tert-butyltetrathiacalix[4]arene have shown that both the sulfuratoms 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 ofthe corresponding complexes of p-tert-butylcalix[4]arene, there is no similarity in the structures of the Cs complexes,with the present structure showing no evidence of polyhapto Cs+−π interactions. Instead, the complex crystallizesas a ligand-bridged (S-, O-donor) aggregate of three Cs ions, solvent molecules, and four calixarenes, somewhatlike the Rb complex, though here four Rb ions are present, and higher in aggregation than the K+ complex,where two K+ ions are sandwiched between two calixarene moieties. The triethylammonium complex of thethiacalixarene monoanion, though formally analogous in that it involves a monocation, has a simpler structurethan 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”, p-tert-butyltetrathiacalix[4]arene ligand itself.
- Structural characterization of the full series of complexes of the group 1 metals with p-tert-butyltetrathiacalix[4]arene shows that the coordination chemistry differs significantly from that of the methylene-bridged calixarene, particularly in that Cs(I) is bound in an oxygen- and sulfur-donor bridged cluster and not through cation−π interactions. There is evidence that thiaether sulfur coordination occurs with all the alkali metal ions.
|
