Multiple Metal Coordination by Calixarenes: A Structure Determination of Relevance to the Use of Calixarenes as Solvent Extraction Agents

Abstract

An insoluble material formed in attempts to extract the copper(II) complex of (R,S)-5,5,7,12,12,14- hexamethyl-1,4,8,11-tetraazacyclotetradecane with the tetraanion of tetrakis(carboxymethyl) p-t-butylcalix[4]arene recrystallizes from pyridine with the composition [Cu(C₁₆H₃₆N₄)] [Na₂(C₅₂H₆₀O₁₂)].2C₅H₅N.4·5H₂O. The crystals are monoclinic, space group P 2₁/c (C⁵_2h, No. 14); a 26·8524(8), b 12·8151(2), c 25·6525(8) Å; β 115·356(1)°. The structure was refined on F² (11379 reflections, 955 parameters), giving conventional R₁ 0·057 (wR₂ 0·118). The calixarene encapsulates two sodium ions and has only tenuous connection to the copper/macrocycle complex through axial coordination of one carboxylate oxygen.