Multiple metal coordination by calixarenes:: A structure determination of relevance to the use of calixarenes as solvent extraction agents

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)] [Na-2(C52H60O12)]. 2C(5)H(5)N(.)4 . 5H(2)O. The crystals are monoclinic, space group P 2(1)/c (C-2h(5), No. 14); a 26.8524(8), b 12.8151(2), c 25.6525(8) Angstrom; beta 115.356(1)degrees. The structure was refined on F-2 (11379 reflections, 955 parameters), giving conventional R-1 0.057 (wR(2) 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.