Phosphoamide – modified p-tert-butyl calix[4]arene and its sodium complexes: Synthesis, coordination ability and structure

A new modified calix[4]arene, namely 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-bis[(tetramethyldiamidophosphinyl)oxy]calix[4]arene (L) has been prepared by reacting the parent calixarene with tetramethyldiamidophosphoric acid chloride, and its structure was solved by the X-ray diffraction method in the solid state and characterized in solution using 1H, 13C, 31P NMR and mass spectral (ES-MS and FAB-MS) data. The coordination ability of L towards Na+ showed the formation of two different complex species, [NaL]+[AuCl4]− · 4H2O (1) and [Na2L2](ClO4)2 · (CH3OH)4 (2), depending on the reaction conditions and nature of the counter ion. Complex 1 is structurally characterized using NMR (1H, 13C, 31P) and mass spectral data. Complex 2 crystallizes with four molecules of methanol, two of them being bridges between two calixarene units and its structure was determined by X-ray analysis.

Graphical abstractThe X-ray structure of the complex [Na2L2](ClO4)2 · 4CH3OH comprises of 2 calix[4]arene ligands, 2Na+, 2(ClO4)− and 4CH3OH. Each of the calix[4]arene ligands participate in the complex, being bonded to Na+ by only one of the PO groups. Both Na+ cations are placed outside of the ligand cavities. Each cation is coordinated to one ClO4- (Na+ is directly bonded to one oxygen of the perchlorate), one terminal and two bridging CH3OH molecules.Figure optionsDownload full-size imageDownload as PowerPoint slide