X-RAY AND NMR INVESTIGATION OF BIS(DIETHOXYPHOSPHORYLOXY)-TERT-BUTYLCALIX[4]ARENE IN THE 1,2-ALTERNATE CONFORMATION

The crystal structure of diethoxyphosphosphoryloxy)-tert-butylcalix[4] arene (1) (hexane solvate, 1:1) was determined by x-ray crystallograph y. The crystal data are P2(1)/n, a = 12.652(1) Angstrom, b = 12.564(2) Angstrom, c = 18.781(4) Angstrom, beta = 105.56(1)degrees, V = 2876.0 (8) Angstrom(3), Z = 2. In this complex the molecule adopts a 1,2-alte rnate conformation. Both the calixarene and hexane molecules are centr osymmetric. The phenol units in the asymmetric part of the calix are i nclined with respect to the main macrocyclic plane by 115.46(6)degrees and 128.01(7)degrees for the phosphorylated and the non-phosphorylate d ring, respectively. Self-inclusion of the ethyl chains in the half-c avities is observed. One intramolecular O-H ... O and several intermol ecular C-H ... O hydrogen bonds are present. In the H-1 NMR spectrum o ne average AX spin system for methylene bridge protons can be interpre ted as fast (on the NMR time-scale) interconversion of non-phosphoryla ted phenol fragments. (C) 1998 John Wiley & Sons, Ltd.