Ethoxy-tethered calix[4]arenes containing P(III) substituents and trimethylsiloxy groups as building blocks in supramolecular chemistry; cis/trans intra- and intermolecular complexation of dichloroplatinum(II) fragments

Abstract

p-tert-Butylcalix[4]arene 1 reacts with bromoethyl acetate and LiAlH4 to form the p-tert-butyl-tetrakis(2-hydroxyethoxy)calix[4]arene 8 bearing four ethyl-spacers at the lower rim of the calixarene. Reaction of 8 with Et2NSiMe3 leads to the tetrakis-substituted derivative 9. Treatment of 9 with PF2Cl gives the stable tetrakis-fluorophosphite 10, while the reaction with 2-chloro-1,3,5-trimethyl-1,3,5-triaza-2σ3λ3-phosphorin-4,6-dione furnishes the tetrakis-substituted molecule 11. When 11 was allowed to react with SO2Cl2, formation of the tetrakis(2-chloro)ethyl substituted calix[4]arene 13 was observed. All examined calixarene derivatives are exclusively obtained in the cone conformer. Reaction of 11 with dichloro(cyclooctadiene)platinum(II) leads to the symmetrically four-times bridged dimmer 15, which exhibits a trans orientation of the atoms surrounding the platinum(II) atom and involves all eight phosphorus atoms in the bridges. When 10 was treated with (COD)PtCl2, the cis intermolecular complex 16 was obtained.